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PUBLIC HEALTH ASSESSMENT

T. H. AGRICULTURE AND NUTRITION COMPANY
FRESNO, FRESNO COUNTY, CALIFORNIA


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

Tables in Appendix B list the contaminants of concern at the THAN site by medium. ATSDR has evaluated those contaminants to determine if exposure to them will affect the public's health. ATSDR's findings are discussed in following sections of this public health assessment.

ATSDR selects and discusses contaminants of concern using the following information (25):

  • concentrations of contaminants on and off site;

  • the quality of field and laboratory data and sample design;

  • comparison of on-and off-site contaminant concentrations with comparison values for noncancer and cancer endpoints;

  • community health concerns.

The listing of a contaminant in the contaminants of concern tables does not mean that it will cause adverse health effects if people are exposed at the specified concentrations. Rather, the listing of a contaminant indicates which contaminants will be discussed further in this public health assessment. When a contaminant is considered to be of concern in one medium, the presence or absence of that contaminant in all media will be discussed. In addition, when a contaminant is considered to be of concern on site, its potential to migrate off-site also will be discussed. The potential for adverse health effects resulting from exposure to the contaminants of health concern is discussed in the Public Health Implications section of this document.

ATSDR uses comparison values--contaminant concentrations in specific media that are believed to protect public health--to select contaminants for further evaluation (25). ATSDR and other agencies have developed the comparison values to provide guidelines for estimating contaminant concentrations in media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values include environmental media guides (EMEGs) and cancer risk evaluation guides (CREGs). EMEGs are media-specific comparison values used to select contaminants of concern based on non-cancer endpoints (25). CREGs are estimated contaminant concentrations expected to cause no more than one excess cancer in a million persons exposed over a lifetime (70 years).

Maximum Contaminant Levels (MCLs) are limits on chemical concentrations in drinking water that U.S. EPA or the California Environmental Protection Agency (Cal/EPA) believes will protect public health (considering the availability and cost-effectiveness of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters water per day (for an adult). Maximum Contaminant Level Goals (MCLGs) are U.S. EPA drinking water health goals set at levels at which no adverse health effects would be expected in exposed persons. MCLs are regulations that can be enforced; MCLGs are goals that are not enforceable. U.S. EPA's reference dose (RfD) and reference concentration (RfC) are estimates of the daily exposure to a contaminant unlikely to cause illness (non-cancer) or injury. In some cases, ATSDR uses comparison values calculated from RfDs. For example, an reference dose media evaluation guide (RMEG) is a contaminant concentration in water or soil at which the exposed individual would receive a dose equal to the RfD from which it was calculated.

Toxic Chemical Release Inventory

During the assessment of the THAN site, the preparers of this document searched the Toxic Chemical Release Inventory (TRI). TRI is an on-line database, maintained by the U.S. EPA, containing information (self reports from chemical manufacturers and other companies throughout the United States) about more than 320 different substances released from facilities into the environment between 1987 and 1991.

On-going facility and/or surrounding facilities emissions may be contributing an additional environmental burden to the nearby population. Therefore, the CDHS staff searched the Toxic Release Inventory (TRI) for the years 1987, 1988, 1989 1990, and 1991 (the years for which TRI data is currently available). TRI contains information on estimated annual releases (emission rates) of toxic chemicals to the environment (via air, water, soil, or underground injection) whether these releases are routine releases, spills and other accidental releases, or occasional releases from normal operation. Toxic chemical release information is submitted to U.S. EPA by certain industries as mandated under the Emergency Planning and Community Right-to-Know Act of 1986.

Since THAN stopped operating in 1981, no information about the facility would be contained in TRI. However, there were environmental releases from other companies located within the zip code area surrounding the THAN site.

In 1987, no companies reported any releases to the air, water, underground injection wells, or the sewer system (26). In 1988, one company reported the release of 40 lbs of chlorine to the City of Fresno sewer system, and another company reportedly released 24 lbs of lead compounds to the air and 13 lbs to the City of Fresno sewer system (27). In 1989, one company reported to TRI that they released 24 lbs of lead to the air and 2,975 lbs of ethylene glycol to the San Joaquin River (28). Another company reported the release of Freon 113 (5,500 lbs) to the air (28).

In 1990, one company reportedly released ammonia to the air (as much as 499 lbs) and to the City of Fresno sewer system (2,562 lbs), lead to the air (24 lbs) and to the City of Fresno sewer system (as much as 10 lbs), and ethylene glycol (3,478 lbs) to the City of Fresno sewer system (29). Another company reported the release of 1,800 lbs of Freon 113 to the air (29). In 1991, one company reportedly released zinc compounds to the City of Fresno sewer system (45 lbs), lead to the air (50 lbs) and to the City of Fresno sewer system (45 lbs), and ethylene glycol (3,700 lbs) to the City of Fresno sewer system (30). Another company reported the release of 1,800 lbs of Freon 113 to the air (30).

A. ON-SITE CONTAMINATION

Surface Soil

On December 12, 1993, DTSC sampled the surface soil (0 to 3 inches) at three locations on the northern edge of the site along McKinley Avenue, outside of the fence that surrounds the rest of the site (61). The three sampling locations are located where no excavations had previously occurred: one sample on the western end, one sample adjacent to where the loading dock had been located; and one sample on the eastern end of the site. DTSC also took surface soil samples at approximately the same points but on the north side of McKinley Avenue (see Off-site Contamination section).

The surface soil samples were analyzed for organochlorine pesticides and organophosphate pesticides (61). All three samples contained DDT (maximum concentration=34 ppm) and DDE (maximum concentration=75 ppm). These maximum concentrations of DDT and DDE detected in surface soil exceed their health comparison values (CREG for DDT= 2 ppm and the CREG for DDE= 2 ppm). No other pesticides were detected in the samples.

Subsurface Soil

THAN has directed several investigations resulting in the analysis of more than 1,400 subsurface soil samples from about 200 locations (1). The subsurface soil samples have been analyzed for volatile organic and semi-volatile organic compounds, pesticides, and inorganic compounds including metals (1).

Eighty six chemicals have been detected in samples collected from subsurface soils at the site. Table 2 lists twenty of the more prevalent contaminants detected in the subsurface soil, the maximum concentration of that contaminant, the depth below ground surface that the maximum concentration was detected, and the number of detections per sample analyses performed for each chemical. The maximum concentrations of twelve compounds listed in Table 2 exceed their corresponding health comparison value and, therefore, are contaminants of concern in the subsurface soil. Comparison values do not exist for four contaminants detected in the subsurface soil and, therefore, they are also selected as contaminants of concern (Table 2).

As a result of these investigations several soil excavations have taken place (Figure 3) (1). Table 2 also lists the contaminants remaining in the subsurface soil after the excavations. The major contaminants of concern that are still present in the soil are DDT, DDD, dieldrin, and toxaphene.

Groundwater-Monitoring Wells

THAN has directed the drilling of several monitoring wells on the THAN site (Figure 6) (1). Several of these wells (#1, 2, 3, 4, and 6) were destroyed during the removal activities at the site in 1988, and monitoring well #77A replaced well #77 in June 1990. The existing monitoring wells include eight wells that screen the A-zone, three wells that screen the B-zone, and one well that screens the C-zone.

THAN initiated on-site groundwater monitoring in 1981 (1). Groundwater monitoring has been performed quarterly since 1984. Between July 1981 and 1983, the groundwater was sampled seven times. The THAN quarterly groundwater monitoring program as of January 1993 includes sampling all the on-site wells if the water levels allow it. The A-zone wells have not been sampled since 1987/1988 because of low water levels.

The water samples have been analyzed for volatile organic and semi-volatile organic compounds, pesticides, and inorganic compounds including metals (1). Table 3 lists the same chemicals found in the on-site subsurface soils and the maximum concentrations of these compounds detected in the on-site groundwater wells by aquifer zone. The most prevalent chemicals detected in the on-site groundwater are DBCP, chloroform, Dinoseb, -hexachlorocyclohexane ( -HCH), lindane, -HCH, dieldrin, and 1,2-dichloroethane.

Groundwater-Private Wells

One private well (well #904) is on the THAN property (1). It was constructed in 1960 and was used for industrial purposes when the site was in operation. The well is screened from 0 to 92 feet bgs. It theoretically draws water from both the A- and B-zones, but primarily from the B-zone since the A-zone has been dry.

THAN began sampling the water from well #904 in March 1992 and continues to monitor it as part of their quarterly monitoring program (1). The water samples from well #904 have been analyzed for volatile organic and semi-volatile organic compounds, pesticides, and inorganic compounds including metals.

The following compounds have been detected in well #904 (historic maximum concentrations are in parenthesis): DBCP (2.20 ppb), DDE (0.07 ppb), DDT (0.09 ppb), dieldrin (0.23 ppb), and nitrate (58,900 ppb). The maximum concentrations of DBCP, dieldrin, and nitrate exceed their corresponding health comparison value and, therefore, are contaminants of concern in the on-site private well.

Air

Site in operation:

Cal OSHA records show that three industrial hygiene inspections took place between 1977 and 1981 (31-33). Overall, the three Cal OSHA inspectors felt that THAN was very cooperative and seemed to have a good safety and health program.

On July 12, 1977, a Cal OSHA inspector conducted an unannounced walk-a-round inspection of the facility and conducted personal air monitoring of seven workers who were formulating DeFend in the hammermill blending area or working in the small packaging area of the plant (32). The DeFend formulation contains dimethoate (approximately 26%) and crystalline quartz. Results showed excessive exposures of 1.3 times the allowable 8-hour time-weighted average (TWA) concentration of nuisance dust (10 mg/m3). The dust samples were analyzed for quartz and found to contain "high levels" but less than the limit of detection. The inspector noted that the employees were wearing "approved respirators." Resampling was deemed "not feasible at this time because condition has changed." The ventilation system that was in place appeared to be ineffective. THAN was required to install a more effective dust control system.

The Cal OSHA inspector found the following entries in the OSHA 200 log for 1976: one skin rash from Guthion and 6 injuries (32). He noted that THAN had several safety procedures in place: biweekly cholinesterase testing, monthly safety meeting, THAN provision of formal respiratory training, respirators, rubber gloves, coveralls, and hard hats, coveralls replaced daily. The inspector noted that THAN seemed willing to cooperate and had no bad history of worker safety.

As a part of a Cal OSHA "Pesticide Emphasis Program," an inspector visited the THAN site on May 24, 1979 (31). He conducted an unannounced walk-a-round inspection. The inspector decided to return at a later date for monitoring because pesticides of concern were not in use that day. The operation taking place that day was Guthion packaging from a holding tank through 3 filling valves into 5-gallon cans. This was an outdoor operation. Employees were wearing coveralls, hats, glasses or face shields, respirators, and gloves. The inspector noted that residues from all the formulation tanks were dumped into an outside sump where they were treated in an open pit and trucked to a Class A landfill.

On October 31, 1979, the Cal OSHA inspector made a follow-up visit during which he conducted full-shift personal sampling on 3 employees and himself for exposure to Trefamid (31). Trefamid contains 50% diphenamid and 3.1% trifluralin. The TWA worker levels of Trefamid were 9.2, 1.6, and 1.1 mg/m3, as compared to 0.06 mg/m3 detected by the personal air monitor on the Cal OSHA inspector. These levels exceed the OSHA Permissible Exposure Limit (PEL) of 1 mg/m3 for trefamid and 0.03 mg/m3 for trifluralin (assuming that 3.1% of the dust is trifluralin). THAN was issued a special order from Cal OSHA that stated that the employees shall not be exposed above the PELs in the future.

Cal OSHA cited the company for issuing the wrong type of respiratory cartridges to the workers; they were wearing ammonia/dust cartridges but should have been wearing pesticide cartridges (31). Cal OSHA also cited THAN for the improper use of the respirators, namely, the workers had the respirators attached with only one instead of two straps. The net result of these violations is that the workers were overexposed to a suspect carcinogen, and their respirators could not have been giving them any significant protection.

A Cal OSHA report dated February 13, 1980, certifies that all unsafe conditions from the above citation had been corrected (31).

On July 1, 1981, a Cal OSHA inspector conducted an unannounced walk-a-round inspection (33). The inspection was precipitated by a Valley Medical Center doctor's report of eye irritation ("burning and stinging") incurred by a THAN employee. The inspection was to determine if control measures were adequate in the Omite area, as Cal OSHA had received 3 reports of dermatitis from Omite. An inspection of THAN's OSHA Log 200 showed that 20 cases of dermatitis due to Omite skin exposure had occurred at THAN, but the majority had not been reported by the treating physician. The inspector sent the list of employees and doctors to Cal OSHA Safety in Fresno for investigation.

THAN management told the inspector that they had instituted mandatory showers twice per shift and the dermatitis problems had disappeared (33). Other health and safety controls in use were a metered system to fill containers, local exhaust ventilation, and personal protective equipment.

During site remediation:

Air monitoring was performed prior to and during removal activities in both 1984 and 1989 (1). Air monitoring was performed in 1988 prior to and during the sampling of building materials and during the removal of 700 cubic yards of previously stockpiled soil in the one-story metal warehouse.

In the spring and summer of 1984, during the extensive soil removal, THAN's contractor conducted dust/aerosol monitoring, organic vapor monitoring, and air sampling adjacent to the work activities and at the site perimeter (1). Dust and vapor suppressants, including the use of commercial foams, were used to control air emissions during the earthwork activities. At no time did the dust/aerosol monitoring detect concentrations of airborne dusts/aerosols above the detection limit (1 mg/m3). Organic vapor monitoring revealed maximum organic vapor concentrations at the site perimeter of less than two parts per million (volume/volume, v/v) over background. Subsequent analysis of vapor samples collected at the site perimeter for volatile organic compounds indicated that vehicle exhaust from on-site internal combustion engines was the source of the majority of organic vapors detected a the site perimeter by the real-time instruments. Perimeter sampling and analyses detected (maximum concentrations in parenthesis) xylenes (7 ppb), DDT (0.068 ppb), lindane (0.270 ppb), and Ethion (0.013 ppb).

Personal air sampling and organic vapor monitoring were performed in January 1988 during removal of soil that was stockpiled in the one-story warehouse (1). Monitoring and sampling were performed adjacent to the soil handling activities and at the site perimeter. Organic vapor monitoring did not detect concentrations of airborne organic vapors above background. Personal air samples (approximate 4-hour samples) were analyzed for DDT. The results were below the detection limits of 0.03 to 0.05 mg/m3.

Personal air sampling and organic vapor monitoring were performed in June 1988 during the sampling of building materials and underlying soil (1). Organic vapor monitoring revealed concentrations of 1 to 3 ppm (v/v) total organics as methane equivalents in one soil sampling hole beneath the ground floor slab of the two-story brick building; the results of subsequent chemical analyses performed on the soil from beneath the building measured DBCP at a concentration of 1 mg/kg and other VOCs below detection limits. At no other sampling locations were organic vapors detected above background. Personal air samples (approximate 8-hour samples) collected during the 1988 building material investigation contained two compounds: 0.2 to 2.0 µg/m3DDT and 0.03 to 0.7 µg/m3 dieldrin.

In early 1989, during the structure demolition and soil excavation, THAN directed the following perimeter air monitoring and sampling: real-time organic vapor monitoring using a portable photoionization detector with a portable flame ionization detector as a backup; 24-hour sampling at five perimeter stations using a hi-volume sampler fitted with a particulate filter and polyurethane foam plug (PUF); and 8 to 24-hour sampling using a low-volume sampler fitted with an absorbent medium (Tenax) (1). The contractor did employ dust and vapor control during the demolition and excavation activities. At each of the hi-volume PUF sampling locations, three 24-hour air samples were collected two weeks prior to commencing demolition work; during the first three days of demolition; and during the first three days of excavation. The samples collected during demolition were analyzed for three indicator compounds: DDT, toxaphene, and dieldrin. The samples collected during excavation were analyzed for four indicator chemicals: DDT, toxaphene, chlordane, and xylenes. Air samples were also collected in the breathing zone of an on-site observer during each work day. The analysis targeted the same indicator chemicals as in the ambient air sampling. General organic vapors were monitored approximately twice-a-day in the breathing zone using an HNu portable organic vapor monitor.

The following are the concentrations detected in the week prior to site activity near the perimeter of the site: DDT, <0.005 to 0.033 µg/m3; dieldrin <0.0003 to 0.0024 µg/m3; toxaphene and chlordane were not detected (<0.0014 µg/m3). The maximum concentrations of DDT and dieldrin detected in the background do exceed their corresponding health comparison levels, DDT- 0.01 µg/m3 (CREG) and dieldrin- 0.0002 µg/m3 (CREG). During building demolition and excavation activities performed in 1989, the maximum airborne concentrations detected were in samples collected during the demolition. The maximum concentrations detected were 0.124 µg/m3 of DDT, 0.0032 µg/m3 of dieldrin, 0.034 µg/m3 of toxaphene. These concentrations exceed theircorresponding health comparison levels. The health comparison value (CREG) is 0.003 µg/m3 for toxaphene and chlordane.

B. OFF-SITE CONTAMINATION

Surface Soil

On December 12, 1993, DTSC sampled the surface soil (0 to 3 inches) at three locations north of the site and on the northern side of McKinley Avenue: one sample on the western end, one sample across the street from where the loading dock had been located; and one sample on the eastern end of the site (61). DTSC also took surface soil samples at approximately the same points but on the southern side of McKinley Avenue (see On-site Contamination section).

The surface soil samples were analyzed for organochlorine pesticides and organophosphate pesticides (61). All three samples contained DDT (maximum concentration=0.80 ppm) and DDE (maximum concentration=1.6 ppm). These maximum concentrations of DDT and DDE detected in surface soil do not exceed their health comparison values (CREG for DDT= 2 ppm and the CREG for DDE= 2 ppm). No other pesticides were detected in the samples.

Subsurface Soil

THAN has directed the sampling of subsurface soil at thirteen locations around the perimeter of the site border and seven locations in the THAN-owned orchard (Figure 7) to investigate the possible migration of contaminated surface water from the site. The subsurface soil samples have been analyzed for volatile organic and semi-volatile organic compounds, pesticides, and inorganic compounds including metals. Five compounds were detected but only dieldrin and toxaphene were detected at levels above comparison values (Table 4).

In 1990, the owners of the 7-acre property on the southeastern corner at the intersection of Temperance and McKinley Avenues contracted with a laboratory to sample and analyze the soil on their property (1). Fresno County Department of Environmental Health asked the owners to test their property for contamination prior to giving them authorization to develop the property. Samples were collected from 0 to 12 inches at two locations on the property and analyzed for pesticides and DBCP. DDT, DDE, and DDD were detected in the samples, but not at levels above comparison values.

Groundwater-Monitoring Wells

THAN has directed the drilling of several monitoring wells not on the THAN site, although some of them are located within the orchards owned by THAN (Figures 7 & 8) (1). The downgradient monitoring wells include six wells that screen the A-zone, fourteen wells that screen the B-zone, nine well that screen the C-zone, and four wells that screen the D-zone. The upgradient monitoring wells include three wells that screen the A-zone, two wells that screen the B-zone, and one well that screens the C-zone. The A-zone wells have not been sampled since 1987/1988 because of low water levels.

THAN initiated the off-site groundwater monitoring well program in 1983 (1). Groundwater monitoring has been performed quarterly since 1984. The THAN quarterly groundwater monitoring program as of January 1993 includes sampling all the off-site wells if the water levels allow it.

The water samples have been analyzed for volatile organic and semi-volatile organic compounds, pesticides, and inorganic compounds including metals (1). Table 5 lists the maximum concentrations of some of the compounds detected in the off-site downgradient groundwater monitoring wells. The maximum concentrations of these compounds detected in upgradient wells are also included for comparison. The main contaminants in the off-site groundwater are DBCP, chloroform, and dieldrin (1).

Groundwater-Private Wells

In July 1980, the Air Pollution Control Office within the Fresno County Health Department sampled the water from the wells of two residences located south of THAN (34). The air district sampled the water from one of the wells after receiving a request from the resident's physician. The resident had become very ill with a high fever of unknown origin which could only be brought down after hospitalization and special treatment. A water sample was submitted to the Fresno County Health Department for bacteriological analysis, the results were negative. Another water sample from the same well was sent to the Sanitation Engineering Section within CDHS for pesticide analysis. The water from the well of the sick resident contained low levels of two pesticides, namely lindane (0.012 ppb) and Endrin (0.001 ppb). No pesticides were detected in the water sample from the well of the other resident.

In December 1980, the well with the pesticides was resampled by the air pollution control district and analyzed by CDHS. Lindane was detected at a very low level, 0.00004 ppb (34).

In early 1981, CDHS sampled the water from eight private wells located in the vicinity of THAN (12). Many of the well water samples contained DBCP at levels above comparison values. The water samples from wells located close to the THAN site contained other pesticides in addition to DBCP, namely lindane, chlordane, dieldrin, and -HCH.

Since 1982, THAN has periodically sampled and analyzed the water from approximately eighty-five private wells (domestic or agricultural) that could be considered downgradient (southeast) from the site (Figure 9) (12). Additionally, THAN has sampled and analyzed the water from twelve private wells that could be considered upgradient from the THAN site.

Since the completion of the extension of the City of Fresno domestic water system to the neighborhood surrounding the site in 1990, THAN samples and analyzes only certain private wells (2). The current domestic well sampling program calls for the testing of at least three wells within the chloroform plume and several wells called peripheral wells that are located at the edges of the plume and are used to detect the potential spread of the plume. If any chemical compounds known to be associated with the site are detected by two or more sampling events, the peripheral well will be added to the domestic well sampling program and wells immediately downgradient of the peripheral well will be added to the peripheral well sampling program. According to the DTSC Order issued to THAN and other respodents, any well yielding a sample containing only DBCP will not be added to the domestic well sampling program or be added to the peripheral well sampling program solely on the basis of the presence of DBCP in the sample.

In the past, the domestic water samples were analyzed for volatile organic and semi-volatile organic compounds, pesticides, and inorganic compounds including metals, although the current analysis protocol includes only volatile organic compounds, pesticides, and DBCP (1). The peripheral well water samples are analyzed for volatile organic compounds and DBCP.

Table 6 is a synopsis of the THAN water analyses of the private wells in the vicinity of THAN (1, 12). The table lists the maximum concentrations detected in private wells located upgradient from THAN, on the THAN property, and downgradient from THAN. The most prevalent chemicals detected in the private wells are DBCP, chloroform, 1,2-dichloroethane, dieldrin, lindane, -HCH, and nitrates. The other chemicals are detected sporadically in various wells, i.e., it is not possible to see a groundwater contaminant plume of any of these contaminants.

DBCP has been detected at a high frequency (90 to 100% of the samples per well) in 75 of the 97 wells. Five of those high frequency detection wells are upgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of 54 of those high frequency detection wells that are considered downgradient to the THAN site. Six of the high frequency detection wells are located at the southwestern tip of the THAN groundwater study area. Ten of these high frequency detection wells are located due south of the THAN site and THAN has not supplied bottled water and has notpaid for the extension of the city water system to replace those wells.

DBCP has been detected periodically (25 to 90% of the samples per well) in 8 of the 97 THAN-sampled wells. Two of the wells are located upgradient to the THAN site. The other 6 wells are located downgradient to the THAN site. THAN has paid for the extension of the city water system to replace the domestic use of 5 downgradient wells.

DBCP has been detected infrequently (less than 25% of the sample analyses conducted per well) in 10 of the 97 THAN-sampled wells . Two of the wells are located upgradient to the THAN site. Four wells are located downgradient to the THAN site, and THAN has paid for the extension of the city water system to replace thesewells. Four of the low detection wells are located southwest of the THAN groundwater study area and are included in the semi-annual groundwater monitoring program conducted by THAN.

DBCP has not been detected in 4 of the 97 THAN-sampled wells. Three of these wells are upgradient from the THAN site.

Chloroform has been detected at a high frequency (90 to 100% of the samples per well) in 17 of the 97 wells. All 17 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all of these wells.

Chloroform has been detected periodically (25 to 75%) in 10 of the 97 THAN-sampled wells. Nine of the 10 wells are locateddowngradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all of these wells.

Chloroform has been detected infrequently (less than 25% frequency) in 10 of the 97 THAN-sampled wells. All 10 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of 9 of the wells.

Chloroform has not been detected in 44 wells. THAN did not analyze for chloroform in 16 wells.

1,2-Dichloroethane has been detected at a high frequency (90 to 100% of the samples per well) in 1 of the 97 wells. This well is located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of the well.

1,2-Dichloroethane has been detected periodically (25 to 75%) in 15 of the 97 THAN-sampled wells. All 15 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all of these wells.

1,2-Dichloroethane has been detected infrequently (less than 25% frequency) in 5 of the 97 THAN-sampled wells. All 5 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all of the wells.

1,2-Dichloroethane has not been detected in 60 wells. THAN did not analyze for 1,2-dichloroethane in 16 wells.

Dieldrin has been detected frequently (86%) in one well that is located downgradient of the site. THAN has paid for the extension of the municipal water system to replace the use of this well. Dieldrin has been detected periodically (25 to 75%) in 3 of the 97 THAN-sampled wells. All 3 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all three wells.

Dieldrin has been detected infrequently (less than 25% frequency) in 7 of the 97 THAN-sampled wells. All 7 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all of those wells.

Dieldrin has not been detected in 67 wells. THAN did not analyze for dieldrin in 20 of the 97 wells.

Lindane has been detected periodically (25 to 75%) in 5 of the 97 THAN-sampled wells. All 5 wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of all of these wells.

Lindane has been detected infrequently (less than 25% frequency) in 14 of the 97 THAN-sampled wells. Eleven of the wells arelocated downgradient to the THAN site, and THAN has paid for the extension of the municipal water system to replace the need for domestic use of those wells. Three of the wells are located due south of the THAN site.

Lindane has not been detected in 60 wells. THAN did not analyze for lindane in 18 wells.

-HCH has been detected periodically (25 to 75%) in 2 of the 97 THAN-sampled wells. Both wells are located downgradient to the THAN site. THAN has paid for the extension of the municipal water system to replace the need for domestic use of both wells.

-HCH has been detected infrequently (less than 25% frequency) in 11 of the 97 THAN-sampled wells. Nine of the wells are located downgradient to the THAN site, and THAN has paid for the extension of the municipal water system to replace the need for domestic use of those wells. Two of the wells are located due south of the THAN site.

-HCH has not been detected in 65 wells. THAN did not analyze for -HCH in 19 wells of the 97 wells.

THAN has analyzed the water from 72 wells for nitrate. Nitrate is not a site-associated contaminant, and thus, the wells have not been analyzed for nitrate as much as for the site-associated chemicals; most of the 72 wells have been analyzed once or twice and a few have been analyzed three times for nitrate. Nitrate has been detected at a level exceeding the drinking water standard (10,000 ppb) in 68 of the 73 wells. In the other 5 wells, the nitrate concentration measured less than 10,000 ppb. Forty-three of the 68 wells with high nitrate levels are no longer used for domestic use since the municipal water system was extended to those properties.

On May 19, 1988, the County of Fresno Health Department collected samples from 53 domestic wells. The samples were analyzed for DBCP and nitrate. This was done in order to assist those residents in deciding whether it was worth incurring the expense of connecting to the City of Fresno water system being proposed by THAN. The residential wells sampled were not associated with the contamination plume being investigated from the THAN site. The wells were located northwest, west, or southwest of the THAN site and along the transmission lines that would be installed for the THAN-sponsored City of Fresno municipal water system extension. The closest well to the edge of the THAN site-associated plume is about 0.5 miles. Of the 53 wells, DBCP was detected (>0.02 ppb) in 32 wells, and the concentration exceeded the health comparison value (MCL= 0.2 ppb) in 23 wells. At that time the County of Fresno used a DBCP health action level, based on a CDHS recommendation, of 1.0 ppb; 11 wells exceeded this level. The nitrate concentration exceeded the health comparison value (45 ppb) in 12 wells. The Fresno County Health Department sent the laboratory results to each homeowner along with a discussion of health effects and possible solutions.

Air

On July 15, 1981, the air pollution control district collected four 1.5 hour air samples at various times during the day, two at one site upwind and one each at two sites downwind (5). There were no odors present during either sampling upwind, but the odors were strong at the two downwind sites during the sampling. The odor was described as "skunkish" (5). The Fresno County Department of Health laboratories analyzed the samples for dimethoate and DEF. Neither DEF (<0.9 ppb) nor dimethoate (<1.7 ppb) were detected in any of the air samples.

C. QUALITY ASSURANCE AND QUALITY CONTROL (QA/QC)

In preparing this public health assessment, ATSDR relied on information provided by U.S. EPA, Cal/EPA, CAL OSHA, Fresno County health department, San Joaquin Valley Unified Air Pollution Control District, and contractors and assumed that adequate quality assurance and quality control measures were followed with regard to chain of custody, laboratory procedures, and data reporting. The validity of the analysis and conclusions drawn in this public health assessment depend on the completeness and reliability of the referenced information.

D. PHYSICAL AND OTHER HAZARDS

No physical hazards appear to be present at the site.

PATHWAYS ANALYSES

To determine whether nearby populations (e.g. residents, workers, schoolchildren, hospital and/or nursing home populations, etc.) are exposed to contaminants migrating from a particular site, CDHS and ATSDR evaluate the environmental and human components leading to human exposure. That pathway analysis considers five elements: sources of contamination; environmental media in which contaminants may be present or from which contaminants may migrate (e.g., air, water, soil); points of exposure; routes of human exposure; and exposed populations (25).

CDHS and ATSDR classifies pathways as completed or potential (25). For a completed pathway to exist, the five elements must exist, and there must be evidence that people have been, are, or could be exposed to a contaminant. A potential pathway exists when at least one of the five elements is missing, but could exist (e.g., people may have been exposed in the past, may now be exposed, or may be exposed in the future). A pathway is eliminated when at least one of the five elements is missing and will never exist (e.g., there are no routes of human exposure).

Table 7 identifies the completed exposure pathways and Table 8 lists the potential exposure pathways. The discussions that follow incorporate only those pathways that are important and relevant to the site.

A. COMPLETED EXPOSURE PATHWAYS

Ingestion, inhalation, and dermal contact with contaminated groundwater from private wells.

Past and in some cases current exposure to contaminated private well water occurred to residents, off-site workers, schoolchildren at Temperance-Kutner School, and the on-site workers. The site-associated groundwater contaminants detected at levels of health concern in the private wells downgradient to the THAN site are chloroform, DBCP, 1,2-dichloroethane, dieldrin, -HCH, and lindane. Groundwater in the eastern sector of Fresno County is also contaminated with nitrate and DBCP at levels above comparison values as a result of the agricultural practices in the area.

The first testing of private wells near to THAN occurred in 1977. Site-associated contaminants were detected in that first test; thus, it is unclear when the groundwater first became contaminated. One estimate of when contaminants migrated from the THAN site comes from modelling the movement of chloroform, a chemical indicator of THAN contamination (1, Appendix R). By using a known concentration of chloroform in the groundwater at a set distance from the site and an estimate of rate of groundwater flow, it is estimated that the groundwater first became contaminated by DBCP from the THAN site in 1979. However, this model does not predict when the area-wide contamination may have begun.

Residents that now use municipal water

Past exposure to contaminated private well water to nearby residents did occur. Most of the wells downgradient of the site are contaminated with DBCP and nitrates. Chloroform (18 private wells), 1,2-dichloroethane (21 private wells), dieldrin (10 wells), lindane (1 well), -HCH (13 wells) has been detected in certain downgradient wells at levels of health concern.

One of the primary routes of exposure was through the ingestion of drinking water and food prepared with contaminated well water.

Volatile compounds can escape as gases during showering, bathing, or cooking and this can also be a significant pathway of exposure. Modelling has predicted that inhalation doses from showering with contaminated water could result in exposures that are greater than those from ingestion (67). U.S. EPA has indicated that the dose from inhalation of volatilized chemicals while showering may be approximately equivalent to the dose from ingestion of two liters per day of the same water.

Absorption of the contaminants through the skin while showering with the contaminated well water or swimming in a pool filled with the contaminated well water may occur but, relative to the ingestion and inhalation exposure routes described above, is less important for the chemicals found in the private well water. Two other potential ingestion exposure routes are the ingestion of homegrown vegetables from gardens watered by the contaminated well water or from dairy products from animals that drink the contaminated well water.

In 1988 bottled water was supplied to 62 residences and workplaces located southeast of the site. Based on this history, residents could have ingested contaminated water for approximately nine years. However, inhalation and dermal exposure to the contaminated water during showering and washing probably continued until 1990, when the municipal water system was extended to those residences. Exposure to the contaminated water may still be occurring if the private well water is used to fill the swimming pool, irrigate the vegetable garden, or to feed livestock.

Off-site workers that now use municipal water

Past exposure to DBCP to off-site workers (school personnel, farm hands, etc.) did occur. The primary route of exposure was through the ingestion of drinking water. It is assumed that other routes of exposure (i.e., showering or eating vegetables from a garden watered with the contaminated water) either did not occur or occurred to only a minor extent.

It is unclear what private wells were used by off-site workers other than the Temperance-Kutner School well that was used by school personnel. Therefore, we analyzed the effect of drinking the school well water by the school personnel and did not consider other off-site worker exposures.

CDHS testing of the Temperance Kutner School well detected DBCP (maximum 0.95 ppb) and lindane (0.06 ppb) (2). The only chemicals to have been detected in the Temperance Kutner well when THAN sampled it (1987 to 1989) are DBCP (maximum-0.78 ppb) and chloroform (maximum-24.0 ppb) (1). THAN also sampled for nitrates (29,000 ppb). Of these chemicals detected in the school well, DBCP, chloroform, and nitrates were detected at levels of health concern.

In 1988, bottled water was supplied to the Temperance-Kutner School and to 62 residences and workplaces located southeast of the site. Based on this history, off-site workers and school personnel could have ingested contaminated water for approximately nine years. Well water is still used to irrigate the school's athletic fields and agricultural and animal husbandry in the area.

School children at Temperance-Kutner School

Past exposure to DBCP, lindane, chloroform, and nitrate-contaminated groundwater from the Temperance-Kutner Scholl well did occur to the children that attended the school. Of these chemicals detected in the school well, DBCP, chloroform, and nitrates were detected at levels of health concern.

The primary route of exposure was through the ingestion of drinking water. It is assumed that other routes of exposure (i.e., showering or eating vegetables from a garden watered with the contaminated water) either did not occur or occurred to only a small extent.

School children at Temperance-Kutner School were probably exposed for a maximum 7 years, from kindergarten to sixth grade.

On-site workers

Past exposure to contaminated well water to on-site workers did occur. THAN began sampling and analyzing their on-site well (well #904) in 1982 and continue to monitor it. The contaminants that have been detected in well #904 are (maximum concentrations detected are in parentheses): DBCP (2.20 ppb), dieldrin (0.23 ppb), DDE (0.07 ppb), DDT (0.09 ppb), and toxaphene (0.2 ppb) (1). THAN also sampled for nitrates (58,900 ppb). Of these chemicals, DBCP, dieldrin , and tozphene were detected in the on- site well at levels of health concern.

The primary route of exposure was from washing and showering with the DBCP-contaminated water. THAN has reported to DTSC that the well was not used for drinking water purposes (66).

On-site workers were exposed to DBCP during showering and washing from 1979, when the groundwater contamination has been predicted to have begun, until the plant closed in 1981, approximately three years.

Residents and off-site workers that use private well water

Past, current, and future exposure to DBCP and nitrates to nearby residents and off-site workers did, does, and will occur. The groundwater in the eastern section of Fresno County is often contaminated from the widespread agricultural use of DBCP and nitrogen-containing fertilizers (35-37).

The primary routes of exposure are through the ingestion of drinking water and food prepared with DBCP- and nitrate- contaminated well water. Volatile compounds like DBCP can escape as gases during showering, bathing, or cooking and this can be a significant pathway of exposure. The absorption of DBCP through the skin while showering with the contaminated well water or swimming in a pool filled with the contaminated well water may occur but, relative to ingestion and inhalation exposure routes described above, is less important. Two other possible exposure scenarios are the ingestion of homegrown vegetables from gardens watered by the contaminated well water or ingestion of dairy products from animals that drink the contaminated well water.

In 1990, THAN financed the extension of the municipal water system and the connection of 62 homes to the system. The City of Fresno offered municipal water connection to other residences along the extension route and not affected by the THAN site. The County of Fresno Health Department sampled and analyzed the water from 53 wells not associated with the contaminant plume; many of these were contaminated with nitrates and/or DBCP. The results were shared with the homeowners. Other residences located along the proposed transmission lines could also pay for the connection, but their well water was not sampled. Some of the residents agreed to pay for the connection. However, some residences chose not to participate, and thus still use their well water for domestic uses.

Other residences located near the THAN site, but not located near the water system extension, did not have the option for connection. These wells may similarly be contaminated with DBCP and nitrate and are still being used.

In 1977, the Fresno County Health Department instituted a DBCP-sampling program for new wells that are constructed in the county. If DBCP is detected at a concentration that exceeds 0.2 ppb (the drinking water standard), the residents are notified and provided with a DBCP fact sheet.

Inhalation of contaminated air by nearby residents and off-site workers

Past exposure to contaminated air may have occurred to nearby workers and residents when the company was in operation. This air contamination may have resulted from the normal facility operations including pouring from containers, filling containers, mixing pesticide formulations without adequate dust collection and vapor treatment, improper waste disposal practices such as the use of open pits, careless handling of raw materials or formulated products, and heavy equipment/truck movement across the unpaved, contaminated soil resulting in dust generation. These exposures stopped when the facility ceased operations. In addition, exposure may have occurred during remediation. There was a slight increase in air levels during the 1989 excavation and building demolition.

There are many indications that volatile sulfur-containing compounds such as dimethoate and DEF did migrate from the THAN site when it was in operation. Dating back to 1969, the Fresno County Health Department (which at that time contained the local air pollution control district) received many odor complaints from nearby residents of THAN (3). The air pollution control district investigated these complaints several times. After one visit to the THAN site, an air pollution control district staff member noted in a memorandum, "I am convinced that their yard, where liquid chemicals have been spilled in the past, is the source of the odor" (7). With direction and supervision by the air pollution control district, THAN took several steps to deal with the odor problem; these included: installing a dust control system, installing a vapor treatment system, storing the chemicals inside a warehouse, etc. However, in 1981, because of the ever increasing number of neighborhood complaints, the air pollution control district ordered THAN to discontinue handling, storing, formulating, mixing, or packaging DEF, Defend, and dimethoate at the site (3).

As has been noted in the Community Concerns Section, long-time residents living around THAN still vividly recall being exposed to odors they believed originated from the THAN site. They described some of the odors as smelling like "rotten eggs" and "cooking cabbage and skunks together"; such descriptions also indicate the presence of sulfur-containing compounds. The odors were often so bad that the residents had to stay inside or "sleep with their face in the pillow." Along with smelling the odors, the residents also complained of health effects such as asthma and other breathing problems, skin irritations and rashes, headaches, and dizziness.

Because sulfur-containing compounds have relatively low odor thresholds, it is understandable that these would be the compounds that the nearby residents would detect. Most of the site-associated compounds are not so odiferous, i.e., they have a higher odor threshold; however, these compounds may also be dispersed through the air as either a gas or attached to dust particles. Thus it is reasonable to assume that the same processing operations that led to the dispersion of the sulfur-containing compounds into the neighborhood would also result in the spread of other compounds when they were being mixed, formulated, packaged, or otherwise handled on-site. This may also explain some of the other odor descriptions and the occasional observance of clouds of chemicals.

Inhalation of contaminated air by on-site workers

Past exposure to contaminated air occurred to THAN employees not wearing adequate respiratory protection when the company was in operation. This air contamination may have resulted from the normal facility operations including pouring from containers, filling containers, mixing pesticide formulations without adequate dust collection and vapor treatment, improper waste disposal practices such as the use of open pits, careless handling of raw materials or formulated products, and heavy equipment/truck movement across the unpaved, contaminated soil resulting in dust generation. Those exposures stopped when operations ceased and did not occur when protective equipment was properly used.

Some of the site-associated chemicals, such as chloroform and DBCP, are considered volatile, easily changing from a liquid form to a gaseous form. Some of the site-associated chemicals such as dimethoate and lindane are termed semivolatile and may be present in a gaseous form and/or attached to dust particles in the air. Some of the chemicals such as DDT, DDE, and DDD are not very volatile and tend to adsorb to soil particles which may be dispersed off-site attached to dust particles.

A 1977 Cal OSHA report indicates that the level of dust in the DeFend formulating area exceeded the OSHA worker health comparison value (32). A 1979 Cal OSHA report indicates that the level of Trifluralin, an active ingredient of Trefamid, in the processing area exceeded the OSHA worker health comparison value (31). Even though employees were wearing respirators during both of these site investigations, during the 1979 visit, the Cal OSHA inspector cited THAN for providing the wrong respirator cartridge filters and allowing the employees to improperly wear the respirators.

Surface soil exposure by on-site workers

Only three surface soil samples (0 to 3 inches bgs) have been taken on-site; therefore, it is not possible to completely evaluate this pathway. In these three surface soil samples, the only contaminants were DDT and DDE. However, the subsurface soil is contaminated with many chemicals namely, aldrin, DDD, DDE, DDT, DEF, 1,2-dichloroethane, dieldrin, Dinoseb, Guthion, -HCH, -HCH, -HCH, lindane, parathion, toxaphene, and trifluralin at levels above comparison values. Since these chemicals may have reached the subsurface soil by deposition onto the surface soil and migration downward, the surface soil is assumed to be contaminated with these contaminants. THAN workers may have been exposed through dermal contact and incidental ingestion to the contamination in the on-site surface soil.

According to a number of industrial hygiene reports (31-33), the majority of workers used gloves, protective boots, and disposable overalls for protection from the chemicals used in the pesticide formulation processes. Thus, these workers would also be protected from the contaminated surface soil. THAN ceased operating in 1981, so those exposures no longer occur. One employee has been retained to monitor the vapor extraction systems and the stormwater drainage system and to maintain a presence at the site. This employee may continue to be exposed to the contaminated surface soil if protective clothing is not worn.

B. POTENTIAL EXPOSURE PATHWAYS

Surface soil exposure to nearby residents and off-site workers

Based on the anecdotal evidence for fugitive dust migrating from the facility when it was in operation, nearby residents and off- site workers may be exposed through dermal contact and incidental ingestion to contaminants in the off-site surface soil. Due to the inadequacy of the off-site surface soil sampling, this pathway is cited as a potential pathway of exposure. The only off-site surface soil sampling that has taken place consists of three sampling locations to the north of the site along McKinley Avenue. DDT and DDE were the only contaminants found in these three samples and the concentrations of DDT and DDE did not exceed their health comparison value. There has been limited off-site subsurface soil sampling; however, this information is not very useful for interpreting typical exposures to nearby residents or off-site workers.

PUBLIC HEALTH IMPLICATIONS

The Public Health Implications section of this public health assessment is divided into three subsections. The first reviews the known, possible toxicological outcomes following exposure to certain site contaminants. The second subsection evaluates available state health outcome database information, reviews prior epidemiological involvement by CDHS, and summarizes several epidemiological studies that have studied the relationship between DBCP-contaminated groundwater in Fresno County and cancer and reproductive toxicity. Given the toxicological information and the available health outcome information, the third subsection addresses specific community health concerns that were recorded in the Community Health Concerns section.

A. TOXICOLOGICAL EVALUATION

The following section evaluates the potential health effects that may result from exposure to contaminants at the THAN site. Populations known or suspected to be sensitive to exposure to the contaminants are included. To link the human exposure potential of a site with health effects that may result from site-specific conditions, ATSDR estimates human exposure to site contaminant(s) by way of ingestion, inhalation, or dermal contact.

In order to understand the health effects that may be caused by a specific chemical, it is helpful to review factors related to how the human body processes a chemical after exposure. Those factors include the exposure concentration (how much), the duration of the exposure (how long), the route of exposure (breathing, eating, drinking, or skin contact), and the multiplicity of exposure (combinations of exposure). Once exposure occurs, individual characteristics such as age, sex, nutritional status, health status, lifestyle, and genetic make-up influence how the chemical is absorbed, distributed, metabolized (processed), and excreted (eliminated). Together, those factors determine health effects that exposed people may have.

To evaluate health effects, ATSDR has developed minimal risk levels (MRLs) for contaminants commonly found at hazardous waste sites (25). The MRL is an estimate of daily human exposure to a contaminant below which noncancer adverse health effects are unlikely. MRLs are developed for ingestion and inhalation and for the length of exposure (e.g., acute, fewer than 14 days; intermediate, 15-364 days; and chronic, more than 365 days).

ATSDR publishes MRLs in its series of chemical-specific documents called Toxicological Profiles--references that describe health effects, environmental transport, human exposure, and regulatory status. Preparers of this public health assessment have reviewed the profiles for the contaminants of concern at the THAN site.

To help with clean-up decisions at hazardous waste site, U.S. EPA has developed reference doses (RfDs). A reference dose is an estimate of the daily exposure of the human population to a potential non-cancer hazard that is likely to be without risk of harmful effects over a lifetime.

If there is no MRL for a particular compound, the preparers of this report will evaluate an exposure using an RfD, if one exists.

U.S. EPA and Cal/EPA have reviewed available information from human and/or animal studies to determine whether certain chemicals are likely to cause cancer in humans. U.S. EPA and/or Cal/EPA have developed cancer slope factor values for many carcinogens. A cancer slope factor is an estimate of a chemical's potential for causing cancer. If adequate information about the level of exposure, frequency of exposure, and length of exposure to a particular carcinogen is available, an estimate of excess cancer risk associated with the exposure can be calculated using the cancer slope factor for that carcinogen. Cancer risks from pathways involving multiple contaminants are added together, and the overall cancer risk from multiple pathways is evaluated.

Cancer risk is the likelihood, or chance, of getting cancer. We say "excess cancer risk" because we have a "background risk" of about one in four chances of getting cancer. In other words, in a million people, it is expected that 250,000 would get cancer from a variety of causes. If we say there is a "one-in-a-million" excess cancer risk from a given exposure to a contaminant, we mean that if one million people are exposed to a carcinogen at a certain level over their lifetime, then one cancer above the background chance, or the 250,001st cancer, may appear in those million persons from that particular exposure. In order to take into account the uncertainties in the science, the risk numbers used are plausible upper limits of the actual risk based on conservative assumptions. In actuality, the risk is probably somewhat lower than that calculated, and in fact, may be zero.

There are no health guidelines available to evaluate exposure through the skin and there are very few inhalation guidelines. In those cases for which exposure via these routes should be evaluated, the use of a MRL, RfD, or a cancer slope factor derived from an ingestion may be used (25).

For many of the compounds of concern at the THAN site, there are insufficient data for ATSDR to evaluate with what health effect, if any, the exposure estimates may be associated. This is because very few chemicals are thoroughly evaluated for toxic effects; the National Research Council estimates that only 2% of at least 60,000 chemicals that are used widely have been comprehensively studied for toxic effect. Many of these chemicals have data from animals testing only. U.S. EPA generally requires the following studies: short-term mutagenicity assays conducted with bacteria or yeast; reproductive toxicity studies; long-term studies in rodent and nonrodent species; and carcinogenicity. The long-term studies do have the ability to detect pathological changes in the organs of most cells but do not test functional changes such as neurologic, neurobehavioral, immune, endocrine, or pulmonary effects.

There are almost no data on the health effects of exposure to multiple contaminants, the situation that typically exists under most site conditions. As a result, effects may be increased or decreased (i.e., exposures to multiple contaminants may cancel out effects expected if a person were exposed to the contaminants individually) when exposure to more than one substance occurs. Simultaneous exposure to contaminants that are known or probable carcinogens could increase the risk of developing cancer. ATSDR's evaluation of exposures in this public health assessment is limited to single contaminant exposures; exposure to multiple contaminants has not been evaluated.

The contaminants of concern which have been selected for follow-up in this section are DBCP, chloroform, 1,2-dichloroethane, dieldrin, lindane, -HCH, -HCH, -HCH, DEF, dimethoate, diphenamid, trifluralin, DDT, DDE, DDD, parathion, and toxaphene. Nitrate, an area-wide groundwater contaminant of concern, will also be discussed. Each of these compounds will be discussed separately. The discussion for each compound will start with a general description of the environmental fate and toxicology of that compound followed by a separate analysis of the health impact to the nearby residents, on-site workers, off-site workers, or schoolchildren at Temperance-Kutner School.

The equations used to calculate dose estimates are described in the Public Health Assessment Guidance Manual (25). The exposure assumptions that were used in calculating the dose estimates referred to in the toxicological evaluation section are listed in Table 9.

1,2-Dibromo-3-chloropropane (DBCP)

General background:

Most of the private wells located in the vicinity of the THAN site are contaminated with DBCP at levels of health concern. The DBCP contamination probably results from both the non-point application by farmers and the inadequate waste handling practices at the THAN site; DBCP that spilled or was applied to the soil does not bind to the soil but leaches to the groundwater.

DBCP was first marketed as a soil fumigant in 1955 (38). Farmers in California stopped using DBCP in 1979. Thus, DBCP could have been used in the eastern sector of Fresno County as a soil fumigant for 24 years. THAN reportedly handled DBCP at the site from 1964 to 1975, eleven years. The first testing of private wells near THAN did not occur until 1977. DBCP was detected in that first test; however, it is unclear when the groundwater first became contaminated. One estimate of when DBCP migrated from the THAN site comes from modelling the movement of chloroform, a chemical indicator of THAN contamination. By using a known concentration of chloroform in the groundwater at a set distance from the site and an estimate of rate of groundwater flow, it is estimated that the groundwater first became contaminated by DBCP from the THAN site in 1979. However, this model does not predict when the area-wide contamination may have begun.

Previous studies of workers in chemical factories that produced DBCP showed that its main harmful effect was to the male reproductive organs (38). Men exposed to DBCP in the air may produce fewer sperm and eventually become unable to father children. Inhalation or ingestion of DBCP by rats or rabbits has been shown to cause male reproductive toxicity (38). One study found sexually mature male rats to be less susceptible to DBCP-induced testicular toxicity than immature male rats (38). Changes that were induced in neonates or in utero were carried on to adulthood. Another study found the degenerative testicular changes in the adult group of rats but not in the immature group.

ATSDR derived an intermediate-duration (15-364 days) oral MRL from information on male reproductive changes noted in rabbits that ingested water spiked with DBCP (38). ATSDR derived an intermediate-duration (15-364 days) inhalation MRL from information on male reproductive changes noted in rabbits that inhaled DBCP (38). There are insufficient study results available for ATSDR to develop either a chronic-duration oral or inhalation MRL.

At high doses, workers exposed to DBCP in the air reported experiencing headache, nausea, light-headedness, and weakness (38). After animals have inhaled or ingested greater amounts of DBCP than those that cause male reproductive toxicity, there is an increased death rate, increase in fetal death, liver and kidney lesions, and cancer. Respiratory lesions and carcinomas of the respiratory tract were observed after inhalation exposure while gastrointestinal lesions and stomach carcinomas were seen after oral exposure in animals. After dermal exposure, DBCP was reported to cause eye and skin irritation and stomach cancer in experimental animals (38).

Information regarding carcinogenicity of DBCP in humans is sparse (38). One report did not find an increased incidence of cancer among exposed workers. A preliminary study suggested an association between lymphoid leukemia and gastric cancers in Fresno County where drinking water was contaminated with DBCP. A later study failed to disprove the association (see Health Outcome Data Evaluation section).

Based on the animal studies, the U.S. Department of Health and Human Services has determined that DBCP may be reasonably anticipated to be a carcinogen (38). The International Agency for Research on Cancer has determined that DBCP is possibly carcinogenic to humans (Class 2B). U.S. EPA has determined that DBCP is a probable human carcinogen (Class B2)(39); however, the cancer potency value for DBCP has been withdrawn by the U.S. EPA. Therefore, the cancer potency used in developing California's MCL will be used to estimate the cancer risk that may have resulted from drinking or showering with DBCP-contaminated groundwater.

Residents that now use municipal water

The daily adult dose calculated from the ingestion of the maximum concentration of DBCP detected in the off-site private wells where municipal water has replaced its domestic use (Table 6) does not exceed the intermediate-duration oral MRL. Therefore, no non-carcinogenic health effects would be expected from ingestion of the maximally DBCP-contaminated water for a period of less than a year. Obviously most residents were not exposed to the maximum concentration; however, most residents were exposed for much longer than a year.

Assuming that the maximum daily dose from inhalation from showering with the contaminated water is equivalent to the maximum daily dose from ingesting the contaminated drinking water, this dose does not exceed the intermediate-duration inhalation MRL. Therefore, the levels of DBCP detected in the private wells would not be expected to result in any adverse health effects if a person was exposed to them for less than a year.

The residents were exposed for much longer than one year to the DBCP-contaminated water; however, there are insufficient long-term, low-dose studies, and ATSDR is not able to develop either a chronic oral or inhalation MRL. Therefore, it is unclear if any non-carcinogenic health effects would be expected to occur from the long-term ingestion or inhalation of the DBCP-contaminated water. It is also unknown what the effects are to more sensitive populations, such as children and the elderly, from either short-term or long-term exposure.

Residents that live near THAN and started using bottled water in 1988 and city water in 1990 may have a low increased risk of cancer (1 in 10,000) resulting from ingesting and breathing the DBCP-contaminated well water.

Off-site workers that now use municipal water

The daily adult dose calculated for the ingestion of the maximum concentration of DBCP detected in the Temperance-Kutner School (Table 6) does not exceed the intermediate-duration oral MRL, and thus, no non-carcinogenic health effects would be expected from ingestion of the maximum level of DBCP in water for a period of less than a year. Obviously not all off-site workers were exposed to the maximum concentration; however, most workers were probably exposed for longer than a year. Because there are no health guidelines for long-term exposure to DBCP, it is unclear if any non-carcinogenic health effects would be expected to occur for exposures greater than one year.

Off-site workers who started using bottled water in 1988 have a very minimal increased cancer risk (1 in 1,000,000) resulting from ingesting the DBCP-contaminated well water.

Schoolchildren at Temperance-Kutner School

Post-adolescent animals have been used for the DBCP toxicology studies. Therefore, there are no data available to evaluate the effect that this exposure may have on children.

On-site workers

The estimated dose to an on-site worker inhaling DBCP while showering and bathing does not exceed the intermediate inhalation MRL. This indicates that noncancer health effects would not be expected to have occurred from exposure to the contaminated water for less than one year. Because there are no health guidelines for long-term exposure to DBCP, it is unclear if any non-carcinogenic health effects would be expected to occur for exposures greater than one year.

On-site workers who showered and bathed with the contaminated water have a very minimal increased cancer risk (1 in 1,000,000) resulting from inhaling DBCP from the contaminated well water.

Residents and off-site workers that use private well water

The daily adult dose calculated from the ingestion of the maximum concentration of DBCP detected in the off-site private wells where municipal water has not replaced its domestic use (Table 6, upgradient well) does not exceed the intermediate-duration oral MRL. Therefore, no noncancer health effects would be expected from ingestion of the maximally DBCP-contaminated water for a period of less than a year. Obviously most residents are not or have not been exposed to the maximum concentration; however, most residents are or have been exposed for much longer than a year.

Assuming that the maximum daily dose from inhalation from showering with the contaminated water is equivalent to the maximum daily dose from ingesting the contaminated drinking water, this dose does not exceed the intermediate-duration inhalation MRL. Therefore, the levels of DBCP detected in the private wells would not be expected to result in any noncancer, adverse health effects if a person was exposed to them for less than a year.

The residents have probably been exposed for much longer than one year to the DBCP-contaminated water; however, there are insufficient study results available for ATSDR to develop either a chronic oral or inhalation MRL. Therefore, it is unclear if any non-carcinogenic health effects would be expected to occur from the long-term ingestion or inhalation of the DBCP-contaminated water.

Residents that live near THAN (east Fresno) and continue to use their private well water may have a moderate increased cancer risk (1 in 1,000) resulting from ingesting and breathing DBCP from the contaminated well water.

 

Chloroform

General background

As a result of how hazardous substances were managed, chloroform was discharged to the on-site soil. Chloroform dissolves easily in water but does not stick to soil very well. This means that if it is spilled onto the soil, it will tend to travel down through the soil to the groundwater. There is almost no chloroform found in the on-site soil. However, the groundwater on the THAN site and 1.25 miles downgradient of the site is contaminated with chloroform at levels of health concern. Chloroform has been detected at levels of health concern in 18 wells located downgradient of the THAN site. Chloroform has also been detected at levels of health concern in the Temperance- Kutner School well.

The first testing of private wells located near THAN for chloroform did not occur until 1984. Chloroform was detected in that first test; thus, it is unclear when the groundwater first became contaminated. One estimate comes from modelling the movement of chloroform from the THAN site. By using a known concentration of chloroform in the groundwater at a set distance from the site and an estimate of rate of groundwater flow, it is estimated that the groundwater first became contaminated with chloroform from the THAN site in 1979.

Chloroform is typically found in chlorine-treated drinking water supplies (40). Drinking water levels as high as 311 ppb have been reported in public water supplies, although most of the reported concentrations ranged between 2 and 44 ppb.

Chloroform was used as an anesthetic, pain reliever, and antispasmodic for many years until its toxic effects were fully recognized and the U.S. Food and Drug Administration banned these uses in 1976 (40). Therefore, most of the information regarding chloroform toxicity following inhalation exposure in humans was obtained from clinical reports of patients undergoing anesthesia. The levels of chloroform used in anesthesia are considerably greater than even the maximum concentrations that residents or off-site workers would have been exposed. Additionally, the exposure duration for chloroform as an anesthetic would be considerably shorter than exposures to residents or off-site workers.

Previous studies have shown that the target organs of chloroform toxicity in humans and animals are the central nervous system, liver, and kidneys (40). The toxicity is very similar whether chloroform is inhaled or ingested. There is no information regarding the developmental or reproductive effects in humans after exposure to chloroform. Animal studies indicate that chloroform can cross the placenta and cause birth defects (40).

ATSDR derived a chronic-duration (greater than 365 days) oral MRL from information on liver changes noted in dogs that ingested chloroform (40). There are insufficient study results available for ATSDR to develop either an intermediate- or chronic-duration inhalation MRL.

Results of studies in humans who drank chlorinated water, which has chloroform in it, showed a possible link between the chloroform in chlorinated water and the occurrence of cancer of the colon and urinary bladder (40). Cancer of the liver and kidney developed in rats and mice that ate food or drank water over a long period of time that had small amounts of chloroform in it. It is not known whether liver and kidney cancer would develop in humans after long-term exposure to chloroform in drinking water. The U.S. Department of Health and Human Services has determined that chloroform may reasonably be anticipated to be a carcinogen (40). Based on sufficient animal studies, the International Agency for Research on Cancer has determined that chloroform may be reasonably anticipated to be carcinogenic to humans. U.S. EPA has determined that chloroform is a probable human carcinogen (Class B2) (39).

Residents that now use municipal water

The daily adult dose calculated from the ingestion of the maximum concentration of chloroform detected in the off-site private wells (Table 6) does not exceed the chronic-duration oral MRL. Assuming that the maximum daily dose from inhalation from showering with the contaminated water is equivalent to the maximum daily dose from ingesting the contaminated drinking water, the ingestion and inhalation daily doses together (or the total dose) does exceed the chronic-duration oral MRL. An estimated chloroform dose lower than the chronic-duration MRL would mean that exposure for longer than 365 days would not be associated with deleterious, noncancer effects. Even though the estimated chloroform dose does exceed the health guidance level, this does not mean that noncancer health effects such as biochemical liver changes will or have occurred, since there are several orders of magnitude safety factor built into the MRL. However, as the does increases the probability of systemic toxicity increases. Most residents were not exposed to the maximum concentration.

It is also unknown what the effects are to more sensitive populations, such as children and the elderly, may be from either short-term or long-term exposure.

Residents that live near THAN and started using bottled water in 1988 and city water in 1990 have a slight increased risk of developing cancer (1 in 100,000) as a result of ingesting and breathing the chloroform in the contaminated well water in the past.

Off-site workers that now use municipal water

The daily adult dose calculated from the ingestion of the maximum concentration of chloroform detected in the Temperance-Kutner School does not exceed the chronic-duration oral MRL, and thus, non-carcinogenic health effects would not be expected from long- term (greater than 365 days) ingestion of the maximally chloroform-contaminated water.

Off-site workers who started using bottled water in 1988 have a very minimal increased cancer risk (less than 1 in 1,000,000) resulting from past ingestion of chloroform in the contaminated well water.

School children at Temperance-Kutner School

Post-adolescent animals have been used for the chloroform toxicology studies; therefore, there are no data available to evaluate the effect that this exposure may have on children.

On-site workers

Chloroform was never detected in the on-site well. Based on historical practices and the monitoring well concentrations, it appears that the on-site private monitoring well is located upgradient to the source of the chloroform contamination, the laboratory building. Therefore, it is assumed that the workers were not exposed to chloroform-contaminated water when showering and washing.

1,2-Dichloroethane

General background

There is very little 1,2-dichloroethane (only 4 detections in 422 samples, Table 2) found in the on-site soil, but the groundwater on the THAN site and 0.9 miles downgradient of the site is contaminated with 1,2-dichloroethane at levels of health concern. 1,2-Dichloroethane does not appear on THAN's chemical inventory and it is not known how it came to be present in on-site soils and groundwater.

The 1,2-dichloroethane groundwater contamination does not extend quite as far downgradient as the chloroform contamination. However, it is assumed that, as with chloroform, the groundwater first became contaminated with 1,2-dichloroethane in 1979. 1,2-Dichloroethane has been detected at levels of health concern in 21 private wells located downgradient of the THAN site.

People who have been accidentally exposed to large amounts of 1,2-dichloroethane in air or who accidentally or intentionally swallowed 1,2-dichloroethane developed nervous system disorders and liver and kidney disease or were known to die from heart failure (41). Studies in experimental animals also found that breathing or swallowing large amounts of 1,2-dichloroethane produced nervous system disorders and kidney disease. Reduced ability to fight infection was also seen in experimental animals who breathed or swallowed 1,2-dichloroethane, but no evidence of this has been reported in humans. Longer-term exposure to lower doses also caused kidney disease in animals. Evidence from animal studies suggests that 1,2-dichloroethane probably does not produce birth defects or affect reproduction (41).

Because of insufficient study results, ATSDR has not developed any non-cancer health comparison values for 1,2-dichloroethane (41). Neither is there an RfD for 1,2-dichloroethane.

Exposure to 1,2-dichloroethane has so far not been associated with cancer in humans (41). However, cancer was seen in laboratory animals who were fed large doses of the chemical. When 1,2-dichloroethane was put on the skin of laboratory animals, they developed lung tumors. Breathing 1,2-dichloroethane may also cause cancer in animals. Based on the cancer findings in animals, the Department of Health and Human Services has determined that 1,2-dichloroethane may reasonably be anticipated to be a carcinogen (41). The International Agency for Research on Cancer (IARC) has determined that 1,2-dichloroethane is possibly carcinogenic to humans. U.S. EPA has determined that 1,2-dichloroethane is a probable human carcinogen (Class B2) (39).

Residents that now use municipal water

ATSDR and U.S. EPA have not developed any health comparison guidelines to evaluate the non-cancer effects of 1,2-dichloroethane. Therefore, it is unclear if any non-carcinogenic health effects would be expected to occur from the ingestion or inhalation of the 1,2-dichloroethane-contaminated water. It is also unknown what health effects are to more sensitive populations, such as children and the elderly, from either short-term or long-term exposure 1,2-dichloroethane.

Residents that live near THAN and started using bottled water in 1988 and city water in 1990 may have a very minimal increased risk of developing cancer (1 in 1,000,000) as a result of past exposure from ingesting and breathing the 1,2-dichloroethane in the contaminated water.

Off-site workers that now use municipal water

1,2-Dichloroethane was never detected in the Temperance-Kutner School well. Therefore, it is assumed that the teachers and other employees of the school were not exposed to 1,2-dichloroethane-contaminated water at school.

School children at Temperance-Kutner School

1,2-Dichloroethane was never detected in the Temperance-Kutner School well. Therefore, it is assumed that the school children were not exposed to 1,2-dichloroethane-contaminated water in school.

On-site workers

1,2-Dichloroethane was never detected in the on-site well. Therefore, it is assumed that the workers were not exposed to 1,2-dichloroethane-contaminated water when showering and washing at the facility.

Dieldrin

General background

Dieldrin has been detected in the on-site subsurface soil, the off-site subsurface soil, the on-site groundwater, and the off-site groundwater at levels of health concern. Dieldrin has been detected at levels of health concern in 10 private wells located downgradient to the THAN site. Dieldrin has also been detected at levels of health concern in the on-site private well.

Dieldrin is a pesticide that was handled at the THAN site from 1960 to 1972. As a result of the waste management practices at the site, dieldrin was discharged to the soil. Dieldrin sticks to soil very strongly and may stay there unchanged for many years (42). Indeed, dieldrin has been detected in the on-site subsurface soil and the off-site subsurface soil at levels of health concern. Dieldrin does not dissolve in water very well (42). Hence, even though the groundwater is contaminated with dieldrin, relative to 1,2-dichloroethane or chloroform, the concentration of dieldrin in groundwater is much less and it has not traveled as far downgradient.

Dieldrin can travel through the air by attaching to dust or as a vapor (42).

Studies show that dieldrin enters the body quickly after exposure. Dieldrin then stays in your body fat for a long time (42). It can take many weeks or years for all of the compound to leave your body.

Information on the effects that occur in humans in response to dieldrin exposure comes from case reports of accidental or intentional poisoning and from studies of workers occupationally exposed in either the manufacture or application of the pesticide (42). The levels of exposure that have occurred as a result of the THAN site would be much lower than the levels in these case studies. Exposure to moderate levels of dieldrin for a long time may cause headaches, dizziness, irritability, vomiting, or uncontrollable muscle movements. This may result from the buildup of dieldrin in the body over time.

Large amounts of dieldrin affect the nervous system of animals similar to that seen in people (42). Animal studies show that dieldrin causes increases in liver enzymes and liver weight. Also, animal studies show that exposure to moderate levels of dieldrin for a short time causes decreased ability to fight infections. It is not known whether dieldrin causes birth defects or reproductive toxicity in humans. Studies in animals give conflicting information about whether dieldrin causes birth defects. Studies in male animals indicated that dieldrin may be associated with decreased fertility (42).

ATSDR derived a chronic-duration (greater than 365 days) oral MRL from information on liver changes noted in dogs that ingested dieldrin (42). There are insufficient study results available for ATSDR to develop an inhalation MRL (42).

Studies in animals show that mice that eat dieldrin develop liver tumors (42). Based on these animal data, U.S. EPA has determined that dieldrin is a probable human carcinogen (Class B2) (39). The International Agency for Research on Cancer has determined that dieldrin is not classifiable as to its carcinogenicity to humans.

Residents that now use municipal water

The daily adult dose calculated from the ingestion of the maximum concentration of dieldrin detected in the off-site private wells (Table 6) does not exceed the chronic-duration oral MRL. Therefore, noncancer health effects would not be expected from long-term (greater than 365 days) ingestion of the dieldrin-contaminated water.

There are insufficient study results available for ATSDR to develop an inhalation MRL. However the ingestion and inhalation daily doses together (or the total dose) does not exceed the chronic-duration oral MRL. Therefore, noncancer health effects would not be expected from ingestion and breathing of the maximally dieldrin-contaminated water.

It is also unknown what the effects are to more sensitive populations, such as children and the elderly, from either short-term or long-term exposure.

Residents that live near THAN and started using bottled water in 1988 and city water in 1990 may have a slight increased risk of cancer (1 in 100,000) from ingesting and breathing the dieldrin-contaminated water in the past.

Off-site workers that now use municipal water

Dieldrin was never detected in the Temperance-Kutner School well. Therefore, it is assumed that the teachers and other employees of the school were not exposed to dieldrin-contaminated water.

School children at Temperance-Kutner School

Dieldrin was never detected in the Temperance-Kutner School well. Therefore, it is assumed that the school children were not exposed to dieldrin-contaminated water.

On-site workers

The estimated dose to an on-site worker inhaling dieldrin while showering and bathing does not exceed the chronic-duration oral MRL. This indicates that noncancer health effects would not be expected to have occurred from exposure to the dieldrin-contaminated water.

On-site workers who showered and bathed with the contaminated water have an very minimal increased cancer risk (1 in 1,000,000) from inhaling dieldrin in the contaminated water.

On-site workers with inadequate protection

If the surface soil is contaminated to a similar extent as the subsurface soil, accidental exposure to dieldrin may have occurred to on-site workers who were not wearing adequate protection. The exposure would most likely have come from the contaminated soil that may be on the workers hands, which is then ingested after typical hand to mouth activity. Additionally, dieldrin is efficiently absorbed through the skin.

There are inadequate surface soil data to allow computation of a maximum daily dose to on-site workers exposed through incidental ingestion and dermal absorption from the contaminated soil.

HCH Isomers/Lindane

General background

The on-site subsurface soil, the groundwater on the THAN site, and the groundwater 0.75 miles downgradient from the THAN site are contaminated with lindane, alpha-hexachlorocyclohexane ( -HCH), beta-hexachlorocyclohexane ( -HCH), and delta-hexachlorocyclohexane ( -HCH) at levels of health concern. Hexachlorocyclohexane (HCH) is a synthetic chemical that exists in eight common chemical forms. One of these forms, gamma-HCH ( -HCH) is commonly called lindane. Lindane was once marketed as an insecticide for fruit, vegetable, and forest crops (43). It is still used in the United States and other countries as a human medicine to treat head and body lice and scabies. Technical-grade HCH, a mixture of several chemical forms of HCH, was once used as an insecticide in the United States; it typically contained about 40% lindane as well as the alpha (), beta (), and delta () forms of HCH.

Lindane and technical-grade HCH were handled at the THAN site from 1960 to 1970. As a result of the waste management practices at the site, these compounds were discharged to the soil. The HCH isomers stick to soil fairly strongly and may stay there unchanged for many years. Indeed, lindane and the other HCH isomers have been detected in the on-site subsurface soil at levels of health concern (43). Lindane and -HCH do not dissolve in water very well (43). Hence, even though the groundwater is contaminated with lindane and the other HCH isomers, relative to 1,2-dichloroethane or chloroform, the concentrations of lindane and the other HCH isomers are much lower and they have not traveled as far downgradient. Lindane has been detected at levels of health concern in one private well located downgradient to the THAN site. -HCH has been detected at levels of health concern in 13 wells located downgradient to the THAN site.

Information about the health effects of HCH comes from occupational studies and studies of individuals that were exposed to lindane through the use of therapeutic lotions to control mites or lice (43). The human health effects of breathing HCH isomers are blood disorders, dizziness, and headaches. These effects have occurred in workers exposed to HCH during pesticide manufacturing. People who have swallowed large amounts of HCH have had seizures and even died. A few people who have used very large amounts of lindane on their skin have had blood disorders or seizures. Animals that have been fed lindane and the other HCH isomers have had convulsions. All isomers of HCH can produce liver and kidney disease. Reduced ability to fight infection was reported in animals fed lindane, and injury to the ovaries and testes was reported in animals given lindane (43).

ATSDR derived an intermediate-duration (15-364 days) oral MRL from information on liver changes noted in rats that ingested the -isomer (43). There are insufficient study results available for ATSDR to develop a chronic oral MRL (43).

No inhalation MRLs have been developed because of the lack of quantifiable human data and the complete lack of animal data (43).

There is no evidence available regarding the presence or absence of carcinogenic effects in humans after exposure to the HCH isomers (43). Long-term administration of -HCH or lindane to laboratory rodents has been reported to result in liver cancer. The Department of Health and Human Services has determined that HCH may reasonably be anticipated to be a carcinogen (43).

Residents that now use municipal water

The daily adult dose calculated from the ingestion of lindane and the HCH isomers (maximum concentrations added together for total dose) detected in the off-site private wells (Table 6) does not exceed the intermediate-duration oral MRL for -HCH exposure. There are insufficient study results available for ATSDR to develop an inhalation MRL. However the ingestion and inhalation daily doses together (or the total dose) does not exceed the intermediate-duration oral MRL for -HCH exposure. For a period of exposure less than a year, noncancer health effects would not be expected from ingestion or inhalation of HCH isomers in the contaminated water.

The residents were exposed for much longer than one year to the HCH-isomer-contaminated water; however, there are insufficient study results available for ATSDR to develop either a chronic oral or inhalation MRL. Therefore, it is unclear if any non-carcinogenic health effects would be expected to occur from the long-term ingestion or inhalation of the HCH-contaminated water.

Residents that live near THAN and started using bottled water in 1988 and city water in 1990 may have very minimal increased risk of developing cancer (1 in 1,000,000) from ingesting and breathing the HCH in the contaminated water in the past. There are currently no exposures.

Off-site workers that now use municipal water

None of the HCH-isomers were ever detected in the Temperance-Kutner School well. Therefore, it is assumed that the teachers and other employees of the school were not exposed to HCH-contaminated water.

School children at Temperance-Kutner School

None of the HCH-isomers were ever detected in the Temperance-Kutner School well. Therefore, it is assumed that the school children were not exposed to lindane or the other HCH- contaminated water while attending school.

On-site workers

None of the HCH-isomers were ever detected in the on-site private well. Therefore, it is assumed that the on-site workers were not exposed to HCH-contaminated water during their showering or bathing at work.

On-site workers with inadequate protection

If the surface soil is contaminated to a similar extent as the subsurface soil, accidental exposure to lindane or the other HCH- isomers may have occurred to on-site workers who were not wearing adequate protection. The exposure would most likely have come from the contaminated soil that may be on the workers' hands, which is then ingested after typical hand to mouth activity. Additionally, the HCH isomers are easily absorbed through the skin.

There are inadequate surface soil data to allow computation of a maximum daily dose to on-site workers exposed through incidental ingestion and dermal absorption from the contaminated soil.

Nitrate

General background

The groundwater in the area of the THAN site is contaminated with nitrate at levels of health concern; it is not a site-associated contaminant, but rather an area-wide problem. Increased nitrate levels in groundwater usually occur as a result of contamination by organic wastes from humans or animals or by nitrogenous fertilizers (44). Nitrates, per se, are nontoxic. The toxic potential of nitrate is related to the conversion of nitrate to nitrite in the gastrointestinal tract. Nitrite is formed from nitrate by certain microorganisms found in soil, water, sewage, as well as in the digestive tract (44).

Inorganic nitrates are also found naturally in foods such as carrots, spinach, celery, lettuce, radishes, and beets and are used as curing agents and preservatives in meat (44). The chief source of the nitrate body burden, except in the newborn, is ingested vegetables, unless drinking water containing high levels is consumed (44).

After being absorbed into the blood stream, nitrite changes hemoglobin so that it is no longer capable of transporting oxygen from the lungs to the tissues (44). This effect is called methemoglobinemia or biochemical suffocation. Ingestion of well water with a high nitrate content produces methemoglobinemia much more frequently in infants than in adults. The current drinking water standard of 10 ppm is an approximate level below which infant methemoglobinemia would be highly unlikely for water that is used for infant feeding. But the margin of safety is little considering that the standard is the maximum concentration at which no observed methemoglobinemia has been associated with water consumption.

There are several other groups of people who may be predisposed to methemoglobinemia due to nitrate/nitrite: pregnant women, individuals with glucose-6-phosphate dehydrogenase deficiency, adults with reduced gastric acidity (including those being treated for peptic ulcer or those with chronic gastritis or pernicious anemia), and people with a hereditary lack of NADH or with a methemoglobin reductase activity in their red blood cells (44).

Limited experimental data do not support the transfer of appreciable amounts of nitrates in milk (44). After a single, high dose of nitrite to animals, it was shown that nitrite passed the placenta to reach the fetus and produced methemoglobinemia. It is hard to extrapolate from these acute animal studies what occurs when humans ingest these chemicals in low levels.

There are reports in the veterinary literature suggesting that nitrite/nitrate exposure increases the incidence of abortions in cattle, but other reports fail to support this observation (44). One study in animals seems to support this effect of nitrate; however, the level at which this was seen was several hundred times that estimated for human intake.

Experimental studies where sodium and potassium nitrate were administered to rat, hamster, mouse, or rabbit have not shown any birth defect effects (44). One epidemiological study suggested a possible association between elevated levels of nitrates in drinking water and increased incidence of malformations of the neural tube and musculoskeletal system. Other possible causative factors such as other dissolved substances in water, dietary parameters, environmental, and personal variations were not investigated.

U.S. EPA has established a RfD for nitrate based on methemoglobinemia effects in infants fed formula prepared with nitrate-containing water (39).

Residents that now use municipal water

The dose calculated that an infant would get from the ingestion of the maximum concentration of nitrate detected in the off-site private wells where municipal water has replaced its domestic use (Table 6) exceeds the chronic RfD. Therefore, methemoglobinemia may have occurred to infants fed formula prepared from the contaminated well water.

Off-site workers that now use municipal water

The noncancer health comparison value is based on infant exposure to nitrates; adult off-site workers would not be expected to have had any noncancer effects from drinking the nitrate-contaminated water.

School children at Temperance-Kutner School

The noncancer health comparison value is based on infant exposure to nitrates; children off-site workers would not be expected to have had any noncancer effects from drinking the nitrate- contaminated water.

On-site workers

The on-site workers did not ingest the water and were, therefore, not exposed to the nitrate in the contaminated water.

Residents and off-site workers that now use private well water

The dose calculated that an infant would get from the ingestion of the maximum concentration of nitrate detected in the off-site private wells still in use for domestic purposes exceeds the chronic RfD. Therefore, methemoglobinemia may have occurred to infants fed formula prepared from the contaminated well water.

S,S,S-tributyl phosphorothioate (DEF)

General background

From 1969 to 1981, numerous nearby residents to the THAN site complained of odors coming from the THAN site. DEF is a sulfur-containing compound with a low odor threshold because of the presence of two impurities--butyl mercaptan and dibutyl disulfide. The odor complaints seemed to coincide with mixing of DEF and Defend (dimethoate, see the following discussion) by THAN. Thus, in 1981, the Fresno County Air Pollution Control District ordered THAN to discontinue handling DEF at their Fresno site.

DEF can exist in the particulate and vapor-phases.

No data were available reviewing the long-term effects to humans or animals that are exposed to DEF.

ATSDR has not developed any MRLs for exposure to DEF. U.S. EPA has not developed an RfD for exposure to DEF (39).

DEF has not been evaluated for its carcinogenic potential by either U.S. EPA (39), the U.S. Department of Health and Human Services, or the International Agency for Research on Cancer.

Nearby residents and off-site workers whom detected odors

Assuming that the residents smelled the butyl mercaptan, a contaminant of DEF, and knowing that the odor threshold for butyl mercaptan is 1 ppb and knowing that prior to 1983 DEF contained 5% butyl mercaptan as a contaminant, the residents may have been exposed 20 ppb DEF. Because the residents altered their lifestyle to avoid the foul odor, it is highly likely that the concentrations were much greater than 20 ppb. Unfortunately, there are no health comparison values to use for evaluating the potential health effects of this exposure concentration.

Dimethoate

General background

THAN handled dimethoate at the site from 1969 to 1981. Dimethoate, also known as De-Fend, is a systemic insecticide used for cotton, sorghum, alfalfa, watermelons, apples, and other fruits. Dimethoate is a sulfur-containing compound with a low odor threshold because of the presence of contaminants (62). Technical dimethoate is about 93-95% pure (62). The major impurities are O,O-dimethyl S-methylphosphorodithioate and O,O,S- trimethyl phosphorodithioate (62).

During the time THAN was in operation at the site, numerous nearby residents complained of odors coming from the THAN site. The odor complaints seemed to coincide with mixing of DEF (see previous discussion) and Defend by THAN. Thus, in 1981, the Fresno County Air Pollution Control District ordered THAN to discontinue handling dimethoate at their Fresno site.

Limited evidence in humans suggests that exposure for longer periods to lower levels of dimethoate may result in damage to the nervous system (45). There have been rare reports of skin sensitization to dimethoate (45).

The major organs or systems affected in laboratory animals by longer-term exposure to lower levels of dimethoate in animals are the liver, kidney, nervous system, the parathyroid, and the male reproductive organs (45). In animals, it is not irritating to the skin and only slightly irritating to the eye. No skin sensitization data are available on dimethoate. Dimethoate did not appear to cause birth defects in experimental animals. However, dimethoate was found to be mutagenic in a variety of in vitro and in vivo test systems.

ATSDR has not developed any health comparison values for dimethoate. U.S. EPA has developed a RfD based on neurotoxicity observed in rats fed dimethoate (39). However, no health comparison values have been developed for the inhalation route of exposure.

Several animal studies suggest that dimethoate may cause tumor formation in a number of different organs including the liver and spleen (45). However, the available data were considered by the International Agency for Research on Cancer to be inadequate to assess the carcinogenic potential of the compound. Dimethoate has not been evaluated for its carcinogenic potential by either U.S. EPA (39) or the U.S. Department of Health and Human Services.

Nearby residents and off-site workers whom detected odors

Assuming that the residents smelled Dimethoate with an odor threshold of 1.06 ppb, the residents were exposed to at least 1.06 ppb dimethoate. Because the residents altered their lifestyle as a result of the foul odor, it is highly likely that the concentrations were much greater than 1.06 ppb. Unfortunately, there are no health comparison values to use for evaluating the potential health effects of exposure through the inhalation route.

Trifluralin

General background

Trifluralin, an herbicide, is an active ingredient in a pesticide mixture called Trefamid. THAN mixed Trefamid at the Fresno site, and as reported by Cal/OSHA on at least one occasion, the on-site workers were overexposed to Trefamid and Trifluralin. Trifluralin is fairly volatile and, therefore, would tend to be present in the air as a vapor (45). However, as result of the mixing of the pesticide mixture it may also be present in air attached to particulates such as the inert material in the Trefamid mixture.

Trifluralin has been detected in the subsurface soil at concentrations that exceed the health comparison level. It is assumed that trifluralin reached the subsurface soil as a result of the waste management practices at the site. Trifluralin is only slightly soluble in water and, thus, is relatively immobile in the soil (45). Hence, the on-site groundwater is only slightly contaminated with trifluralin and not at a level of health concern.

Trifluralin is a dinitroaniline and considered to have a very low degree of toxicity and is easily degraded in the environment to products without significant adverse effects on organisms (45). Trifluralin is not considered to be either an eye or skin irritant. Trifluralin has not demonstrated any developmental toxicity in animal studies (45).

ATSDR has not developed any health comparison values for trifluralin. U.S. EPA has developed a reference dose (RfD) based on liver and blood changes observed in dogs fed trifluralin (39).

Based on no human studies and limited animal studies, U.S. EPA classifies trifluralin as a possible human carcinogen (Class C) (39).

On-site workers with inadequate protection

On at least one occasion, on-site workers were exposed to trifluralin in the air at a level that exceeded the acceptable worker exposure concentration. Assuming that the workers did not wear adequate respiratory protection and were exposed to the maximum detected trifluralin for the entire employment, the exposure dose exceeds the RfD for trifluralin. An estimated trifluralin dose lower than the RfD would mean that long-term exposure would not be associated with deleterious, noncancer effects. Even though the estimated trifluralin dose does exceed the health guidance level, this does not mean that noncancer health effects such as liver and blood changes occurred, since there are several orders of magnitude safety factor built into the RfD. However, as the does increases the probability of systemic toxicity increases.

Making the assumption that a worker was employed by THAN the entire time that it operated at this site (1959 to 1981) and the worker was exposed to the maximum concentration of trifluralin detected during the Cal OSHA inspections without adequate respiratory protection for that entire time of employment, the worker may have a slight increased cancer risk (1 in 100,000) from this exposure.

If the surface soil is contaminated to a similar extent as the subsurface soil, accidental exposure to trifluralin may have occurred to on-site workers who were not wearing adequate protection. The exposure would most likely have come from the contaminated soil that may be on the workers' hands, which is then ingested after typical hand to mouth activity. Additionally, trifluralin is easily absorbed through the skin.

There are inadequate surface soil data to allow computation of a maximum daily dose to on-site workers exposed through incidental ingestion and dermal absorption from the contaminated soil.

Diphenamid

General background

Diphenamid, an herbicide, is an active ingredient in a pesticide mixture called Trefamid. THAN mixed Trefamid at the Fresno site, and as reported by Cal/OSHA on at least one occasion, the on-site workers were overexposed to Trefamid. Diphenamid is not very volatile and, thus, would be present in the air as a particulate.

THAN handled diphenamid at the site from 1965 to 1979. As a result of the waste management practices diphenamid was discharged to the on-site soil. Diphenamid has been detected in the subsurface soil but not at levels that exceed the health comparison level. Diphenamid does not bind very tightly to sandy soils and, thus, it leaches rapidly to the groundwater. The on-site groundwater is contaminated with diphenamid at a level of health concern. Diphenamid has been detected in the off-site groundwater but not at a level of health concern.

ATSDR has not developed any MRLs for exposure to diphenamid. U.S. EPA has developed a RfD based on liver changes noted in dogs fed diphenamid (39).

Diphenamid has not been evaluated for its carcinogenic potential by either U.S. EPA, the U.S. Department of Health and Human Services, or the International Agency for Research on Cancer.

On-site workers

On at least one occasion, on-site workers were exposed to diphenamid as a result of wearing inadequate respiratory protection while formulating Trefamid, which contains 50% diphenamid. Assuming that a worker was exposed to the maximum detected diphenamid for an entire shift, the exposure dose exceeds the RfD for diphenamid. An estimated diphemamid dose lower than the RfD would mean that long-term exposure would not be associated with deleterious, noncancer effects. Even though the estimated diphenamid dose does exceed the health guidance level, this does not mean that noncancer health effects such as liver changes occurred, since there are several orders of magnitude safety factor built into the RfD. However, as the does increases the probability of systemic toxicity increases.

DDD, DDE, DDT

General background

The on-site subsurface soil is contaminated with DDD, DDE, and DDT at levels of health concern. DDT was one of the most widely used insecticides until its use was banned by U.S. EPA in 1972 because DDT was building up in the environment and because some cancer tests in laboratory animals showed positive results (46). DDE and DDD are contaminants of technical grade DDT. In the soil, DDT is usually broken down to form DDE or DDD. DDD was also marketed as a pesticide, and one form of DDD has been used medically to treat cancer of the adrenal gland (46).

THAN handled DDT and DDE at the site from 1965 to 1972. As a result of the waste management practices at the site, DDT and DDD were discharged to the on-site soil. Once in the environment, DDT lasts for a very long time (46). DDT, DDE, and DDD attach tightly to soil and are not very water soluble; therefore, they do not tend to move down through the soil to the groundwater (46). Indeed, DDT, DDE, and DDT have been rarely detected in water samples taken from wells both on and downgradient from the THAN site, indicating that the DDT, DDE, and DDD in the soil is not moving from the soil to the groundwater. DDT, DDE, and DDD attached to soil particles may be carried by the wind. If near to the surface, some of the DDT and the DDE may vaporize.

Short-term exposure to high doses of DDT through accidental or intentional poisoning primarily affects the nervous system (46). People who made DDT had some changes in the levels of liver enzymes. However, there was no indication that DDT caused permanent, harmful (noncancer) effects. Animal studies show that long-term exposure to DDT may affect the liver (46).

ATSDR has not developed an intermediate- or chronic-duration oral MRL.

U.S. EPA has developed a RfD based on liver changes observed in rats fed DDT (39).

Studies in animals have shown that oral exposure to DDT can result in an increased occurrence of liver tumors (46). In studies of DDT-exposed workers, results did not show increases in the number of deaths or cancers. However, these studies had problems or flaws so that possible increases in cancer may not have been detected. Because DDT caused cancer in laboratory animals, it is assumed that DDT could have this effect in humans. The Department of Health and Human Services has determined that DDT may reasonably be anticipated to be a human carcinogen (46). The International Agency for Research on Cancer (IARC) has determined that DDT, DDE, and DDD are possibly carcinogenic in humans. U.S. EPA has determined that DDT, DDE, and DDD are probable human carcinogens (Class B2) (39).

On-site workers with inadequate protection

Limited surface soil sampling has detected DDT and DDE at levels of health concern. More extensive sampling has shown DDT, DDE, and DDD to be major contaminants in the subsurface soil. Therefore, accidental exposure to DDT, DDE, or DDD may have occurred to on-site workers who were not wearing adequate protection. The exposure would most likely have come from the contaminated soil that may be on the workers' hands, which is then ingested after typical hand to mouth activity. Even though the contaminated soil is on the skin, DDT, DDE, and DDD do not enter the body through the skin very easily.

Even though the data are limited, the surface soil data for DDT and DDE were used to compute a maximum daily dose to on-site workers exposed through incidental ingestion of the contaminated soil. The estimated dose for a former employee not wearing adequate protection, thereby accidentally ingesting DDT and DDE- contaminated surface soil, does exceed the RfD. An estimated DDT/DDE dose lower than the RfD would mean that long-term exposure would not be associated with deleterious, noncancer effects. Even though the estimated DDT/DDE dose does exceed the health guidance level, this does not mean that noncancer health effects such as liver changes occurred, since there are several orders of magnitude safety factor built into the RfD. However, as the dose increases the probability of systemic toxicity increases.

Since both DDT and DDE are considered to be probable human carcinogens by U.S. EPA, former employees that did not wear adequate protection and who were exposed for 13 years, may have a moderate (1 in 1,000) increased cancer risk from exposure to DDE and DDT present in soil.

Parathion

General background

The on-site subsurface soil is contaminated with parathion at levels of health concern. THAN handled parathion at the site from 1959 to 1981. As a result of the waste management practices at the site, parathion was discharged to the on-site soil. Parathion in soil will vaporize to air or stick to soil particles and does not dissolve easily in water (45). There is very little parathion found in the groundwater on or near the THAN site, indicating that it is not migrating from the subsurface soil to the groundwater.

Limited evidence in humans suggests that exposure for longer periods to lower levels of parathion may result in damage to the nervous system (45). The nervous system is the major organ system affected in laboratory animals exposed long-term to low-levels of parathion. Parathion may be fetotoxic, but it does not seem to be associated with any developmental toxicity.

ATSDR has not developed any non-cancer health comparison values for parathion. Neither is there an RfD for parathion (39).

One animal study has suggested that parathion may be associated with an increased incidence of adrenal cortical tumors (45).

Based on no human studies and limited animal studies, U.S. EPA classifies parathion as a possible human carcinogen (Class C) (39). The International Agency for Research on Cancer determined that there is inadequate evidence for the carcinogenicity of parathion in animals.

On-site workers with inadequate protection

If the surface soil is contaminated to a similar extent as the subsurface soil, accidental exposure to parathion may have occurred to on-site workers who were not wearing adequate protection. The exposure would most likely have come from the contaminated soil that may be on the workers' hands, which is then ingested after typical hand to mouth activity. Additionally, parathion is easily absorbed through the skin.

There are inadequate surface soil data to allow computation of a maximum daily dose to on-site workers exposed through incidental ingestion and dermal absorption from the contaminated soil.

Toxaphene

General background

The on-site subsurface soil is contaminated with toxaphene at levels of health concern. Toxaphene is an insecticide that was heavily used in the United States until most uses of it were banned in 1982 (47). Toxaphene is a man-made mixture containing over 670 chemicals, primarily various chlorinated camphene compounds.

THAN handled toxaphene at the site from 1959 to 1965. As a result of the waste management practices at the site, toxaphene was discharged to the on-site soil. Toxaphene in soil will vaporize to air or stick to soil particles and does not dissolve easily in water (47). There is very little toxaphene found in the groundwater on or near the THAN site, indicating that toxaphene is not migrating from the subsurface soil to the groundwater.

Limited evidence in humans suggests that exposure for longer periods to lower levels of toxaphene may result in damage to the liver, kidneys, lungs, and nervous system in people (47). The major organ or systems affected in laboratory animals by longer-term exposure to lower levels of toxaphene are the liver, kidney, nervous system, adrenal gland, and immune system. The adrenal gland and immune system don't appear to be damaged by toxaphene in people.

ATSDR derived an intermediate-duration (15-364 days) oral MRL from information on developmental changes noted in offspring of rats fed toxaphene during gestation (47). ATSDR derived an acute-duration (less than 14 days) oral MRL from information on hepatic changes noted in rats fed toxaphene (47). There are insufficient study results available for ATSDR to develop a chronic oral MRL (47).

No conclusive evidence is available to link cancer with toxaphene exposure in humans (47). However, an increased risk for developing cancer (liver and thyroid) has been demonstrated in laboratory rodents exposed to high doses of toxaphene. Based on these findings, U.S. EPA has classified toxaphene as a probable human carcinogen (Class B2) (39).

On-site workers with inadequate protection

If the surface soil is contaminated to a similar extent as the subsurface soil, accidental exposure to toxaphene may have occurred to on-site workers who were not wearing adequate protection. The exposure would most likely have come from the contaminated soil that may be on the workers' hands, which is then ingested after typical hand to mouth activity. Additionally, toxaphene may be easily absorbed through the skin.

There are inadequate surface soil data to allow computation of a maximum daily dose to on-site workers exposed via incidental ingestion and dermal absorption from the contaminated soil.

B. HEALTH OUTCOME DATA EVALUATION

Cancer Registry

The CDHS California Cancer Registry has been collecting cancer incidence data for Fresno County since 1988. Under the state model of reporting, a passive cancer surveillance system has been implemented in which hospitals and other facilities are responsible for identifying, abstracting, and reporting cancer cases to regional registries. The regional registries report to the state. Cases are identified by trained tumor registrars.

Cancer incidence data for the two census tracts that include the THAN site were obtained from the California Cancer Registry. For the 4 year period 1988-1991 (the years for which cancer reporting is complete), there were a total of 182 cancers diagnosed in residents of these two census tracts (63). Fifteen different sites of cancer were diagnosed in the time period. In general, cancer is a disease of older people, and in this population, greater than 80% of the cases were diagnosed in people forty and older. There were only 5 cases diagnosed in young people less than 20 years of age. Table 10 presents the distribution of cancers by organ types in the two tracts of interest compared to Fresno County as a whole. Cancer incidence in the two tracts does not appear to be unusual and is very similar to that seen for Fresno County as a whole. The top four sites (accounting for more than 50% of the cases for both the tracts and the county as a whole) are respiratory cancers, cancers of the digestive system, male genital, and female breast. There are limitations to using these kinds of data, and it cannot be concluded that hazardous materials present at the site did or did not affect cancer incidence among the residents of the tracts of interest.

Birth Defects Monitoring Program

The CDHS Birth Defect Registry Program (BDMP) began collecting data for Fresno County in 1986. As of 1991, the data are no longer being collected in Fresno County. BDMP staff used to periodically visit all non-military hospitals and genetic centers in California and nearby bordering areas to review medical records (17). Diagnostic and demographic information was collected from in-patient and genetic center medical charts for children diagnosed with major structural malformations between conception and 1 year of age (17). The zip code coding for a particular birth was determined by using the mother's residence at the time of delivery. This still occurs in those regions where BDMP is still active.

CDHS (ATSDR Cooperative Agreement staff) requested the birth defect incidence data for the THAN site area. BDMP has provided the data according to zip code, the smallest geographical area by which data are readily available, for the years 1986 to 1990 (64). The reported birth defects were classified into eleven categories according to organ system: central nervous system, eye, ear, heart, lung, oral clefts, gastrointestinal, genitourinary, skin, musculoskeletal, and chromosomal anomalies and other congenital anomalies. Although this grouping of birth defects is more specific than considering all malformations as a single group, individual malformations within each group may not be etiologically homogeneous.

For 1986 to 1990, the overall case rate and individual organ systems rates were calculated for the zip code containing the THAN site. In order to determine whether there was an increase in the rate of birth defects among children born to women living in that zip code, these rates were compared to the overall case rate and organ system specific rates for Fresno County (excluding the zip code) and the entire state.

Out of a total of 4,333 births (live births and fetal deaths) in the zip code during the five year period, 127 cases of birth defects were identified (64). This gives an observed overall rate of birth defects of 29 per 1,000 births. The overall rate of birth defects in Fresno County for the same time period was 31 per 1,000 births. When the birth defects were grouped by organ system, the rates for the zip code surrounding the THAN site were either comparable or lower than the rates for the rest of Fresno County or the rest of the state.

Because the zip code is much larger than the THAN site (Figure 5), any birth defect incidence rates for the zip code may not be directly linked to the site. These data rely on the address at time of delivery to reflect the address during the first three months of pregnancy, the time of maximum susceptibility to teratogens for many types of birth defects. It is known that 20- 25% of mothers change residence between conception and birth. Another limitation to this cursory look at health outcome data is that many confounding factors such as mother's age, mother's race, child's sex, and parent's socioeconomic status were not taken into account.

The birth defect incidence data for the years 1986-1990 do not reflect an increase in birth defects in the zip code that includes the THAN site (64). However, because of the many limitations to using these types of data, this does not mean that hazardous materials present at the site did or did not affect reproductive outcomes for women living near the site.

Prior CDHS Involvement

In 1989, Environmental Epidemiology and Toxicology Section (EETS) staff reviewed the two health-related data bases: the cancer registry and the birth defects registry (48). Based on information for 1987 and one-half of 1988, adult cancers had not increased (48). Preliminary information from the Birth Defects Monitoring Program showed no increases in low birth weight babies for 1987 (48). They also reviewed childhood cancer data available from a large four county study being conducted by other EETS staff. They reported to the T-K Neighbors that examination of the child cancers reported between 1980 and 1988 found no evidence of excessive numbers nearby the site (48).

Then in 1990, in response to a request from the T-K Neighbors for a health study, staff from within CDHS reviewed the environmental consultant reports concerning THAN and assessed the possibility that adverse health effects might result from groundwater contamination (49). The CDHS staff found that the community around THAN "is unlikely to experience an increased incidence of adverse health effects as a result of the off-site groundwater contamination" (49). CDHS shared the risk estimate assumptions and results with the community and T-K Neighbors. Due to the low level of exposure and the small size of the potentially affected population, they explained that a health survey would not shed any light on whether the illnesses reported in the community represented the normal, expected occurrences that any such community would have, or whether there were some subtle risks present because of the site.

DBCP Groundwater Health Studies- Fresno Area

The area-wide DBCP groundwater contamination problem has been the subject of several epidemiological studies that have focused on cancer or reproductive endpoints. In 1982, EETS within CDHS carried out a preliminary epidemiological study to test whether DBCP contamination in the drinking water in Fresno County was associated with cancer deaths. Specifically, they looked at deaths from 1970-1979 due to esophageal, stomach, liver, kidney, female breast, and lymphoid leukemia (cancers associated with DBCP in laboratory animals) (50). The report states that they found statistically significant trends of increasing risk for stomach cancer and lymphoid leukemia associated with increasing DBCP exposure (50). The apparent effect was greater than one would have expected from animal toxicology studies. In the report, CDHS pointed out that the study was exploratory in nature, and that the findings might have a number of other explanations, i.e., people of Hispanic ethnicity may live in high DBCP use areas, and Hispanics are known to have higher rates of stomach cancer.

Shell Oil Company retained a consultant to reanalyze the CDHS study and to conduct a case-control study in which relatives of individuals who died of gastric cancer or who had died of other causes were interviewed (51). The study included the same outcomes as those in the CDHS study but extended the study period to 1970-1984, used narrower age strata, and used seven DBCP contamination strata rather than three as in the CDHS study. They conclude "there is no evidence of association between DBCP in Fresno County water and mortality from leukemia or gastric cancer" (51).

A review of the Shell report by two California state agencies conclude that even though the Shell study corrects some of the flaws of the CDHS study, like controlling for Hispanic ethnicity, the data still demonstrate a suggestive association between DBCP exposure and gastric cancer and lymphoid leukemia mortality (52, 53).

The Shell Oil Company consultant extended their DBCP study to look at reproductive outcomes from 1978-1982. Specifically they looked at birth rates, birth weight, and birth defects. The DBCP contamination by census tract was again divided into seven strata. The seven DBCP contaminant levels are as follows (Categories 1-7, respectively): <0.010 ppb, 0.010-0.100 ppb, 0.100-0.200 ppb, 0.200-0.500 ppb, 0.500-1.000 ppb, 1.000-3.000 ppb, and >3.0 ppb.

No correlation was found for birth ratios adjusted for age, race, percent Hispanic, and parity and DBCP contamination (54). There was no statistical trend across the seven DBCP exposure categories for low birth weight; however, five of the higher exposure categories showed an increased relative risk for low birth weight compared to the lowest exposure category (55). The highest exposure category did result in a low birth weight that was statistically significant compared to the lowest exposure category (55).

The relative risks for all congenital malformations for infants born in the census tracts of the six higher DBCP exposure categories were lower than the comparison group (55). However, central nervous system (neurological) birth defects were all greater in the six higher DBCP exposure categories compared to the lowest exposure category (55). There was no dose related trend to this finding (55).

C. COMMUNITY HEALTH CONCERNS EVALUATION

As was explained in the Community Health Concerns Section, the residents have consistently and urgently expressed concerns about exposures from the THAN site. As a way to document the extent and nature of the health and environmental concerns, which had been raised by the community members for many years, CDHS staff conducted interviews in the neighborhood surrounding the THAN site. A comprehensive synopsis of their concerns can be found in the Community Health Concerns section. In this section, the experiences that were recorded in that section will be reviewed for plausible explanation and understanding, given the known toxicology of the site-associated compounds and history with similar exposures at other sites. However, it should be pointed out that while certain plausible connections may be drawn, other explanations that bear no relationship to site-associated compounds are also possible. Since we were not conducting a health study, we did not attempt to identify all the possible confounding factors.

Some of the residents whom we interviewed were exposed to certain site-associated chemicals that were released into the air when the site was in operation. Some of the residents we interviewed were exposed to site-associated chemicals and nitrate in their private wells when they used the water for domestic purposes. Some residents that we interviewed were exposed through both of these pathways.

The residents whom we interviewed who lived in close proximity to the site remember very vividly the "rotten egg" odors or "skunk smells" that used to arise from mixing of certain formulations at the site. These odors were probably attributable to DEF or Defend or the impurities in these pesticide formulations. Interestingly, the residents remember smelling the odors on the weekends, especially when it was hot and humid and in the evenings, yet according to information related to DTSC, THAN, site operations ceased in the late afternoon and no mixing occurred on the weekends (66). Weekends and evenings are the times that people are typically at home, so they might not have been home to experience the odors at other times of the day or week. It is also probable that the hot weather would increase the volatilization of materials stored or spilled on-site and that the humid weather would cause these compounds to concentrate. Hot and humid weather is usually present when there is an inversion layer due to pressure differences in the atmosphere. Fog, or in some cases smog, may result from the presence of an inversion layer, and investigators from the U.S. Department of Agriculture have detected an enriched amount of pesticides in fog in the San Joaquin Valley (56). Diazinon, parathion, chlorpyrifos, and DEF were detected at much higher levels in the fog samples collected in the San Joaquin Valley compared to what concentrations are found in rainwater or would be expected based on the chemical properties of the pesticides (56). Thus, while not being expected, the temporal occurrences of the odor memories by the residents could be plausibly explained.

Many of the residents remember experiencing health effects when they smelled the odors. These health effects included skin problems, numbness in fingers and lips, difficulty breathing, nausea and diarrhea, and central nervous system effects like headache, delirium, and poor coordination. The odor threshold (concentration at which a compound can be smelled) for most compounds is lower than the concentration that is known to be associated with a health effect (57). An odor threshold is simply the minimum concentration at which a compound can be detected by an individual. Humans also have the ability to detect the intensity of an odor, and it has been shown that odor intensity perception is proportional to the concentration of the odorant (57). Residents living near the site described odors that would awaken them at night, cause them to sleep with their head in a pillow, and prevent them from going out into their backyard. It seems apparent that the responsible odorants were present at concentrations much higher than their odor thresholds. Therefore, the odor-related health effects that the residents reportedly experienced should not be dismissed as not being expected based on toxicology or being "psychological" in origin (58). As was pointed out in the toxicological evaluation section, very little is known about the low level health effects of DEF or Defend.

For many years, health effects have been reported by communities in San Joaquin or Imperial Valley potentially exposed to the drift of cotton defoliants sprayed in nearby fields. In one study, investigators found eye irritation, runny nose, throat irritation, fatigue, nausea, and diarrhea to be statistically elevated in respondents living or working in three communities located near sprayed cotton fields than in a control group (59). The most frequently applied cotton defoliants in these areas are DEF and another compound that rapidly degrades to DEF (59). Low levels of DEF were detected in the air of the three communities located near fields (59).

To protect public health, the California Department of Pesticide Regulation does not allow DEF to be applied within one-half mile of residential areas. This regulation does not apply to pesticide formulation facilities. However it should be noted that no such safety zone existed around the THAN formulation site. The nearest residence to the THAN site is less than 500 feet from the facility's border.

Another epidemiological study looked at a northern California community located right beside a potato field where Ethoprop (a sulfur-containing cholinesterase inhibitor very similar to DEF and Defend) was sprayed (60). They found an elevated level of risk for self-reported headache, diarrhea, runny nose, sore throat, burning/itching eyes, fever, hay fever attacks, and asthma attacks in the group of people that perceived a strong or unusual odor compared to the group that did not perceive any odor (60).

In addition to the concerns about air exposures to site-associated chemicals, many residents we interviewed were concerned about the contaminated well water. Several of the interviewed residents were concerned enough that they switched to bottle water or bought a carbon filter system early in the 1980s. However, they reported that the contaminated water was good at keeping their plants' "pest free." Others continued to use the water but reported experiencing headaches, diarrhea and stomach pains, nose and throat irritation, and skin problems.

DBCP and dieldrin are known to cause headaches but at higher concentrations than residents probably were exposed. Several of the site-associated chemicals found in the contaminated groundwater--chloroform, 1,2-dichloroethane, and dieldrin--are known to be associated with gastrointestinal problems like nausea, vomiting, diarrhea, and stomach pain but at higher concentrations than residents probably were exposed. None of the compounds are necessarily associated with nose and throat irritation. High levels of DBCP when applied to the skin of animals did cause skin inflammation. It should be noted that headaches, stomach aches, and skin irritation are frequently experienced in the general unexposed population.

The residents whom we interviewed reported that they and their family members had been diagnosed by their physicians for a variety of conditions and diseases. Heart-related conditions were the most predominant and included irregular heartbeat, tachycardia (excessively rapid heartbeat), hypertension, and congestive heart failure. Also reported were liver degeneration, immunological depression, neurological alterations, inability to conceive due to low sperm count, and several miscarriages.

Chloroform and dieldrin have been associated with heart/blood system-related health effects but at much higher concentrations than would have been experienced at the THAN site.

Liver changes have been associated with human exposure to chloroform, 1,2-dichloroethane, and technical-grade-HCH, but these effects would not be expected based on the toxicological evaluation of exposure through the private well water.

Immunological function tests are not required by Federal or state regulatory agencies, and no federal standards for immune system tests in animals have been established. However, DBCP, chloroform, 1,2-dichloroethane, and the HCH isomers including lindane have been shown to depress or alter the immune system response in some way. It is not known whether these effects would be seen at the concentrations to which the residents have been exposed.

Neurological testing using animals to see the effect of compounds is also not standardized. Additionally, animal testing may not be appropriate because many of the neurological conditions or syndromes seen in humans do not appear to occur in evolutionarily less developed animals like rodents. High concentrations of dieldrin have been associated with convulsions. The HCH isomers are known to cause paresthesia, seizures, and altered brainwave patterns.

As stated in the toxicological section, we have inadequate knowledge about the health effects that might result from long-term, low level exposure to any one of the compounds. However, using what we do know, long-term exposure to the maximum concentration of DBCP detected in the private wells may result in effects on the reproductivity in men, specifically, lowered sperm count. Lindane has been shown to affect the male and female reproductive organs, but no evaluation could be made as to whether these effects would be expected at the concentrations detected in the private well water. Nitrate has been associated with miscarriages in animals; it is not known whether the levels of nitrates detected in the private well water could be associated with miscarriages in women.

The residents reported to us the occurrence of several types of cancer, colon cancer being the most common. DBCP, 1,2-dichloroethane, dieldrin, and HCH isomers including lindane are thought to be cancer-causing based on animal studies, though there are little human data to support the animal data. Epidemiology studies have suggested an association between chronic exposure to chlorinated drinking water sources and increased incidences of colon cancer and bladder cancer. Chloroform is a by-product of chlorination. In the Toxicological Evaluation section, each of the compounds detected in the private well water were evaluated for their carcinogenic impact. The increased cancer risk for the maximal concentrations detected in the private well water varied from minimal (less than 1 person in 1,000,000 people) to low increase (1 person in 10,000 people). Remember that 1 in 4 people (2,500 in 10,000 people) will contract cancer sometime during their lifetime. Thus, instead of 2,500 of 10,000 people getting cancer within their lifetime, there would be 2,501 people with cancer. The size of the exposed population is so small that it would be impossible to detect this type of increase in a health study.

Toxicologists draw on all available and newest information to evaluate the human health impact from the compounds at the site. However there are significant gaps that limit a complete understanding of the human health impact to residents living near to the THAN site. Very little is known about the initiation and progression of the many different types of cancer. Very little is known about the toxicological interactions that may occur when a human is exposed to a chemical mixture. For instance, if a chemical depresses the immune system, how would the body be altered and would this alteration affect the way the body responds to another compound that is known to cause cancer or affect the reproductive system. There are many questions still unanswered in environmental health science.

In addition to human health concerns, respondents expressed many health concerns related to their pets and farm animals. Disruption of the breeding cycle, sterility, miscarriages and premature births were cited as problems with cattle and sheep. Several female dogs had cancer of the mammary glands. Several pets with leukemia were reported. Skin rashes and irritations were reported among cats and dogs. Although many of the animal health problems continued when human problems generally ceased with the closing of the THAN and/or the use of bottled water or another drinking water source. This could be explained by the fact that most of the residents that we interviewed, continue to use their private well as the source of water for their domestic animals. As previously described, DBCP and nitrates, as well some other site-associated contaminants, found in the contaminated groundwater are associated with reproductive problems, skin irritation, and cancer. There may be a correlation, but a more thorough evaluation of the animals' health effects is beyond the scope of this public health assessment.

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