PUBLIC HEALTH ASSESSMENT
GULFPORT, HARRISON COUNTY, MISSISSIPPI
Review of sampling data and supporting site-related information suggests that contaminants have been released to ambient air, groundwater, soil, surface water, and sediment. ATSDR staff also searched the EPA Toxic Chemical Release Inventory to determine whether it included pertinent information about industrial chemical releases to ambient air or other media. That database showed four companies (listed below alphabetically) in the Chemfax vicinity that reported releasing chemicals to air in 1991, the latest reporting period available (3):
Arizona Chemical Company: Reichold Road, (about 3½ miles east of Chemfax)
- Total air release, 48,915 pounds--consisting of ammonia, benzene, biphenyl, ethylbenzene,
maleic anhydride, naphthalene, styrene, sulfuric acid, toluene, xylene
Avondale Industries: 13303 Seaway Road, Gulfport (about 1½ miles east of Chemfax)
- Total air release, 34,800 pounds--acetone
Indal Aluminum: 1900 34th Street, (about 2½ miles south of Chemfax)
- Total air release, 13,000 pounds--chlorine
Treated Materials Co.: 13334 Seaway Road, Gulfport (about 1½ miles east of Chemfax)
- Total air release, 30 pounds--consisting of compounds of chromium, arsenic, and copper
Chemical release data are reported as pounds of chemical released per year. The information does not include ambient air concentration information and, therefore, is not useful for addressing specific public health considerations.
ATSDR reviewed information and selected contaminants that warrant evaluation in later sections of this document to decide whether exposure to them has public health significance. Contaminant selection considered the following factors:
- Concentrations of contaminants in media;
- Sample locations, field data quality, and laboratory data quality;
- Relationship of concentrations to ATSDR's selection comparison values or the unavailability
of suitable comparison values; and
- Community health concerns.
Many contaminants evaluated during this process were eliminated from further review and are not mentioned in this document. Those that the process identified for further evaluation and their associated environmental media are summarized in this section and in data tables (Appendix B). However, discussion of the selected contaminants and affected environmental media in this section of the assessment does not imply that human exposure has occurred or would actually result in adverse health effects. Later sections address exposure and health effects issues.
The data tables include selection comparison value information where pertinent. The Cancer Risk Evaluation Guide (CREG) is an estimated comparison concentration that is based on an excess cancer rate of one in a million persons and is calculated using EPA's cancer slope factor for a specific chemical. ATSDR's Environmental Media Evaluation Guide (EMEG) is an estimated comparison concentration that is based on health effects information determined by ATSDR for its Toxicological Profiles for specific chemicals.
Ambient Air Quality
In December, 1993, ATSDR's representative was on the property on two successive days and noted a chemical odor. The odor was stronger on the second day; a company manager said the plant was at a higher production level than the previous day.
Table 1 (Appendix B) reports selected airborne contaminants identified by sampling conducted on site on three days within the same week in the spring of 1990. Comparison of the maximum contaminant levels (Item A in the table) with values reported in the apparent upwind (Item B) and downwind (Item C) directions appears to confirm that chemical air emissions occur within the property boundaries. Four of the maximum concentrations (Item A) were less than 1 part per billion (ppb). Four concentrations ranged between 1 and 10 ppb (1,2,4-trimethyl-benzene; 1,3,5-trimethylbenzene; trichlorofluoromethane; and trichlorotrifluoromethane); several were found between 10 and 100 ppb (1,2,4-trimethyl-benzene; benzene; methylene chloride; naphthalene; and xylene); and one (styrene) was 120 ppb. Five chemicals (benzene, carbon tetrachloride, methylene chloride, naphthalene, and styrene) were at levels greater that their associated selection comparison values, as shown in Table 1.
ATSDR reviewed the chemical concentration data and the apparent upwind sampling locations on site to consider whether chemicals might have blown onto the property from off-site sources during the monitoring event. That review also sought to identify concentrations at which chemicals might have been transported from the site onto adjacent property while sampling was in progress. ATSDR considers those evaluation findings to be speculative but informative. Comparison of Item B (upwind) concentrations to the Item A sampling data suggests that some airborne chemicals at low concentrations were being transported onto the property. ATSDR especially noted that the Items B and A concentrations were about the same for 1,1,1-trichloroethane; 1,2,4-trichlorobenzene; carbon tetrachloride; and dichlorodifluoromethane. Such similarities suggest that the sources of those specific chemicals, and possibly others, might be entirely off site. The Item C (downwind) data suggest that, for the most part, the concentrations of airborne chemicals transported off the property during that sampling event might have been on the order of 1 ppb or less.
Monitoring and Industrial Wells
Table 2 (Appendix B) provides maximum concentrations of the selected contaminants recorded during 1988 and 1990 sampling activities for on-site groundwater in monitoring wells and industrial wells (Table 2, Items A and B). The table also contains off-site monitoring data recorded at two well locations several hundred feet northeast and southeast of the property along Three Rivers Road (Item C). Neither of the off-site wells is between the site and the Industrial Seaway, a possible discharge point for contaminated shallow groundwater.
Four organic chemicals were present in the on-site monitoring wells but were absent in samples from the industrial wells and the off-site monitoring wells. Several metals found in on-site and off-site monitoring wells at relatively similar concentrations were largely absent from samples drawn from the on-site industrial wells. Two metals, lead and nickel, were identified in monitoring well samples at levels greater than their associated selection comparison values, as shown in Table 2. Most metals shown were at levels that are within the range frequently found in groundwater. Cobalt is above its normal range, but the concentrations shown also have been found elsewhere. Aluminum, iron, and lead levels are somewhat greater than normal.
Public Water Supply Wells
ATSDR received a set of sampling information for four of the nearest public supply wells in the area; the closest is nearly a mile northeast of the site, beyond the Industrial Seaway. Data included a range of metals and several other common water quality parameters (5). Sample dates ranged from 1975 to 1992. Concentrations reported were well within accepted drinking water limits; hence these constituents were not selected for further consideration in this document. Organic chemical data were not included in the analyses.
Results of 15 surface soil samples taken on site in 1988 and 1990 show several of the selected organic chemicals present at substantive concentrations (Table 3, Appendix B). One chemical, p,p'dichlorodiphenyldichloroethane (4,4-DDD), was identified at an estimated (approximate) concentration greater than its associated selection comparison value. Three samples taken off site on adjacent properties on the north side of County Barn Road show two of the selected organic chemicals were present at quite low levels; wind might have transported contaminated particles there and elsewhere from one or more of the area industries. Metals were at similar concentrations on site and off site; the levels shown are within the range normally found in soils.
Sampling of subsurface soils on site in 1990 identified the selected organic chemicals shown in Table 4 (Appendix B); the chemicals were not detected in off-site subsurface soils. Metals concentrations were comparable on site and off site; the levels shown are within the range normally found in soils.
Several selected organic chemicals were present in sediment sampling in 1988 and 1990 (Table 5; Appendix B) on site in ditches and holding ponds (Table 5, Item A), within a diked tank area (Item B), and in the former cooling pond before it was closed (Item C). The highest concentrations were found in ditches and holding ponds. A few organic chemicals were found--but at substantially lower levels--in sediment samples obtained at two locations off site from the ditch (Item D) through which both on-site and off-site drainage water is transported to Bernard Bayou. None of the selected chemicals were detected in sediments sampled at a location that is believed to reflect background conditions (Item E). Some metals were at substantively higher concentrations on site than off site, but the levels shown are within the range normally found in soil-like material.
One selected organic chemical and several metals were present in 1990 in pond waters on site (Table 6, Appendix B); a few metals were present in a sample of water from an off-site ditch that transports both on-site and off-site runoff. The metals concentrations are generally within the range normally found in natural waters.
ATSDR is not aware of data for off-site ambient air or for nearby private water wells that might be affected by site releases. ATSDR also is not aware of pertinent sediment and water quality data for the nearby Industrial Seaway. However, ATSDR's review of data for the off-site drainage ditch sediment and surface water suggests that inflows of those materials into the Industrial Seaway are likely to be negligible when compared to the massive inflows area-wide from land runoff and industry discharges. Thus, it is likely that specific site effects, if any, on Seaway water and sediment quality could not be measured.
ATSDR noted that laboratory analyses for sample data used in these evaluations were subjected to quality control. ATSDR presumes that field and associated protocols were substantially valid. The completeness and reliability of information could affect the validity of ATSDR's conclusions.
ATSDR did not observe substantive physical or other hazards on the property. The
concentrations of organic chemicals reported in on-site ambient air are much less than required to support ignition or an explosion.
ATSDR identifies completed and potential human exposure pathways by examining source, and environmental and human components that might lead to contact with contaminants. A pathway analysis considers five elements:
- A source,
- A contaminated medium (e.g., soils, waste materials, air),
- A point or location of human exposure,
- A route of exposure (ingestion, inhalation, or skin contact), and
- An exposed population.
An exposure pathway is considered complete when all five elements exist and there is evidence that exposure to a contaminant has occurred in the past, is occurring, or will occur in the future. An exposure pathway is considered to be potential when one or more key elements are not clearly defined but could exist. Potential pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring, or could occur in the future. For this assessment, ATSDR's analysis of information indicates there are several completed pathways. The principal one is associated with ambient air; the others involve surface soils, workplace chemicals, and the combination of sediment and surface water. A few potential pathways also are plausible. This section describes pertinent information about those pathway elements; Table 7 (Appendix B) summarizes pathway information.
Discussion of pathways in this section does not imply that human exposure would actually result in adverse health effects. Health issues are addressed in the Public Health Implications section of this assessment.
Principal Completed Exposure Pathway
Ambient air sampling conducted on the Chemfax property indicates that Chemfax workers have been exposed consistently in the past, are being exposed, and will be exposed in the future through inhalation to chemicals such as those shown on Table 1. Reports of odors and respiratory disorders received from persons within an extended area indicate that various groups of area workers, shoppers, temporary and long-term residents, and students have also been exposed, are being exposed, and will be exposed in the future through intermittent inhalation of airborne chemicals that appear to be from multiple sources. The specific chemicals released by all industries in the area are not known but would include at least those identified in EPA's Toxic Chemical Release Inventory.
Other Completed Pathways
From experience with assessments of other chemical facilities and the site visit, ATSDR representatives believe that some Chemfax workers likely have been exposed in the past, are being exposed, and will be exposed in the future to process chemicals during intermittent equipment maintenance, chemical loading/unloading procedures, and related production activities principally through incidental skin contact and inhalation.
Workers on site likely have been exposed, are being exposed, and will be exposed to contaminants in surface soils principally through intermittent skin contact, incidental ingestion, and inhalation. Limited sampling data for off-site soils suggest that persons on at least portions of the immediately surrounding properties also are likely to have been exposed, are likely to be exposed currently, and are likely to be exposed in the future to low levels of some contaminants through the same intermittent exposure routes.
Sediment and Surface Water
Some contaminants have been shown to be present in surface water or sediment in on-site ponds, ditches, and diked areas and in an off-site ditch. A few maintenance workers have probably experienced exposure to those contaminants in the past, presently experience exposure, and are likely to experience exposure in the future principally through intermittent skin contact and incidental ingestion, while conducting activities at those locations.
Private Water Supply Wells
Before 1978, workers on site might have been exposed to the types of contaminants shown in monitoring well samples through ingestion and other potable uses of water from the formerly used private supply well. Sample data were not reported for that well.
Water company representatives helped ATSDR identify several nearby locations, including an adjacent business, that are not connected to any of the public water systems. For purposes of this public health assessment, ATSDR presumes that at least some of those people rely on private wells for potable water supply. None of those locations are between the site and the Industrial Seaway, a plausible discharge point for shallow contaminated groundwater. Off-site groundwater monitoring at two locations along Three Rivers Road has not disclosed contaminants at levels of concern. However, that limited data and the on-site data are not sufficient to confidently predict groundwater flow direction(s) in the site vicinity. Without specific knowledge of groundwater quality at locations that might be on private wells, ATSDR investigators believe some business personnel and residents in the area have been, are being, and are likely to be potentially exposed to contaminants through ingestion, inhalation (while showering and cooking), and skin contact with groundwater.
Residents' descriptions of what they have seen in Seaway waters (e.g., floating tar-like substance)
suggest that boaters, fishermen, and any swimmers might have experienced, might be
experiencing, and might experience intermittent exposure to contaminants principally through
skin contact and incidental ingestion. Fishermen might also be exposed to contaminants through
consumption of fish. Pertinent sampling data are not known to be available for these media.
Sediment is not likely to be an important medium for direct exposure unless they have been
dredged and deposited where human contact could occur.
This section discusses health issues for persons exposed to specific contaminants, discusses health outcome data and addresses specific community health concerns. To evaluate noncancer health effects, ATSDR has developed a Minimal Risk Level (MRL) for certain contaminants commonly found at hazardous waste sites. The MRL is an estimate of daily human exposure to a contaminant below which noncancer adverse health effects are unlikely to occur. MRLs are developed for routes of exposure and for the length of exposure: acute (less than 14 days), intermediate (15 to 364 days), and chronic (equal to or greater than 365 days). ATSDR presents these MRLs in Toxicological Profiles. These chemical-specific profiles provide information on health effects, environmental transport, human exposure, and regulatory status. If an ATSDR MRL is not available, then EPA's Reference Dose (RfD) is used. The RfD is an estimate of daily human exposure to a contaminant for a lifetime below which (noncancer) health effects are unlikely to occur.
In order to determine levels of exposure to calcium, iron, magnesium, potassium, and sodium, the estimated ingestion exposures are compared with values derived from the Recommended Dietary Allowances (RDAs) and ranges of Estimated Safe and Adequate Dietary Intakes (ADIs). The RDAs are the levels of intake of essential nutrients that, on the basis of scientific knowledge, are judged by the Food and Nutrition Board of the National Research Council (NRC) to be adequate to meet the known nutrient needs of practically all healthy persons. The ADIs are ranges of provisional values of recommended use when data are insufficient to set RDAs.
ATSDR estimates cancer risks using EPA's cancer potency factor. That method assumes that animal data gathered under high dose exposure conditions can be used to estimate the risk of low dose exposures in humans (6). Cancer is a group of diseases characterized by uncontained growth and spread of abnormal cells. Cancer cells multiply uncontrollably, destroying normal cells, and can spread from their site of origin to other parts of the body. A chemical capable of causing damage leading to cancer is called a carcinogen. The latency period, or length of time between exposure and development of disease, ranges from a few years to decades.
Health Issues by Contaminant
The mere presence of a chemical does not imply that harm will result from exposure. A contaminant at a concentration lower than that chemical's MRL or RfD should pose no appreciable public health hazard with respect to noncancerous adverse health effects.
Individuals likely have been exposed, are being exposed, and will be exposed to multiple contaminants through several exposure pathways. However, scientific data on the health effects of multiple contaminant exposure are very limited. The effects of multiple contaminant exposure can be additive, synergistic (greater than the sum of the effects of single-contaminant exposures), or antagonistic (less than the sum of the effects of single-contaminant exposures). Also, simultaneous exposure to contaminants that are known or probable human carcinogens could increase the risk of developing cancer. Evaluation of exposures in this public health assessment is based mainly on separate individual contaminant exposures.
To estimate the exposure dose, it was assumed that adults (mainly workers in respect to this site) and non-pica children would ingest 50, and 100 milligrams (mg) of soil per day respectively. Pica children exhibit a craving for unnatural food such as soil. Soil ingestion rate in pica children (5,000 mg per day) greatly exceeds the soil ingestion for the normal population. Children 1 to 3 years old are at increased risk of pica behavior but probably did not have access to soils, contaminated sediments and waste locations at this site because those areas are not within their reach. For incidental ingestion of surface water by workers on site, we assumed an ingestion rate of 1 milliliter (0.001 L) per day.
Polynuclear Aromatic Hydrocarbons (PAHs)
PAHs are naturally occurring or synthetic chemicals formed during the incomplete burning of fossil fuels such as coal, oil, and gas and other organic matter. There is little known use for most of these chemicals except for research purposes. A few PAHs are used in medicine and to make dyes, plastics, and pesticides. Reliable health-based and environmental information exists on only a few of the 17 PAHs discussed in the ATSDR toxicological profile for PAHs, and the potential health effects of the other less well-studied PAHs must be inferred from this information (7).
Workers at the Chemfax site, nearby residents, and workers at other immediately surrounding businesses off site likely were exposed, are being exposed, and will be probably exposed in the future to naphthalene in air (Table 1) and surface water (Table 6) and to several PAHs in surface soils (Table 3) and sediments (Table 4). It is also very likely that some workers have been exposed, are being exposed, and will be exposed in the future to chemicals including PAHs during equipment maintenance and chemical loading/unloading procedures, principally through incidental skin contact and inhalation. However, it is difficult to determine whether health effects would occur, because data and other information are absent.
Reliable health-based information exists on only a few of the 17 PAHs discussed in the toxicological profile. Since these chemicals often occur together in the environment and many have similar health effects, potential health effects of the other less well-studied PAHs in this document will be inferred from this information (7). There are no MRLs or RfDs for benzo(a)anthracene, benzo(b/k)fluoranthene, benzo(ghi)perylene, indeno(1,2,3-cd)pyrene, 2-methylnaphthalene, and phenanthrene. However, the total ingestion dose of all these PAHs in surface soils on site did not exceed the RfDs for either anthracene (0.3 milligram per kilogram per day (mg/kg/day), fluoranthene (0.04 mg/kg/day), fluorene (0.04 mg/kg/day), acenaphthene (0.06 mg/kg/day), pyrene (0.03 mg/kg/day) or the acute MRL for benzo(a)pyrene (0.1 mg/kg/day). In addition, the total dose is between 1,000 and 10,000 times lower than the dose of a mixture of PAHs that caused minor liver problems or aplastic anaemia in laboratory animals (9). Noncarcinogenic health effects are unlikely to occur in workers and nearby residents because of exposure to low levels of PAHs in surface soils on site and off site.
Workers at Chemfax likely were also exposed to naphthalene in air and surface water (Tables 1 and 6). The inhalation exposure for workers on site does not exceed ATSDR's chronic inhalation MRL of 0.002 parts per million (ppm) for naphthalene. In addition, the maximum concentration (12 ppb or 0.012 ppm) of naphthalene in ambient air at Chemfax (Table 1) is lower than the acceptable ambient air concentrations set by most states in the United States. Moreover, harmful effects and symptoms are known to begin to occur in humans only at short and long term inhalation exposures of 10 ppm. Most of the 30 to 60 workers at Chemfax are unlikely to experience any adverse health effects because of exposure to this level of naphthalene in air.
The very small number of maintenance workers are those most at risk, because they are exposed to PAHs in air (Table 1), surface soils (Table 3), sediments (Table 5), and in surface water (Table 6). It is possible that this small group of workers might receive high levels of PAHs in their bodies and that the exposure could cause mild headaches and nausea. In addition, any hypersensitive people among these workers might also experience minor skin irritations because of their exposures to high PAHs in soils and sediments.
Workers at Chemfax will be potentially exposed in the future to PAHs in groundwater (Table 2). However, the potential estimated doses do not exceed the RfDs for acenaphthene, fluorene, fluoranthene, pyrene or benzo(a)pyrene. Moreover, the total estimated ingestion dose from all groundwater, sediments, and surface water was more than 1,000 times lower than the experimental dose that caused minor liver problems or aplastic anaemia in laboratory animals (9). Therefore, adverse noncarcinogenic health effects are unlikely to occur because of potential exposure to low levels of PAHs in groundwater.
The Department of Health and Human Services/ National Toxicology Program (DHHS/NTP), the International Agency for Research on Cancer (IARC), and the United States Environmental Protection Agency (EPA) consider benzo(a) anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and ideno(1,2,3-c,d)pyrene to be probable or possible human carcinogens that have caused forestomach, esophageal, and laryngeal tumors in laboratory rats. ATSDR used the toxicity equivalency factor (TEF) methodology in conjunction with the benzo(a)pyrene dose-response model and the dose additivity assumption to obtain estimates of cancer risk associated with exposures to PAHs in surface and subsurface soils, sediments, and groundwater. Based on these estimates, the small number of maintenance workers at Chemfax exposed to the highest levels of PAHs in surface soils and sediments might have a low increased risk of developing stomach, laryngeal, or esophageal tumors in their lifetime. If any soil-pica children are exposed in nearby off-site areas to the low levels of PAHs recorded, they have no apparent increased risk of developing cancer.
Potential exposure to PAHs in groundwater on and off site (Table 2) could pose a public health hazard because levels of some contaminants in monitoring/industrial wells both on and off site exceed natural background levels or health guidelines. Potential exposure to contaminants in subsurface soils on site can be avoided if any future remedial or construction workers wear protective clothing and follow prescribed guidelines.
Other Organic Chemicals
Workers at Chemfax likely were exposed, are being exposed and will be exposed in the future to other organic chemicals in air, groundwater, surface soils, and sediments (Tables 1-3 and 5). However, none of the contaminants were detected in the off-site environmental media sampled (Tables 2-6).
Information in the Environmental Contamination section and environmental data presented in Table 1 indicate that levels of benzene, carbon tetrachloride, methylene chloride, and styrene in ambient air far exceed their associated selection comparison levels. The concentrations of all other contaminants were far lower than their comparison values or levels commonly found in air. Benzene, carbon tetrachloride, methylene chloride and styrene, which are also known carcinogens, are discussed further in this section.
Benzene, also known as benzol, is a clear, colorless, and highly flammable liquid with a strong sweet odor. Benzene evaporates into the air very quickly and dissolves easily in water. Benzene found in the environment is from both human activities and natural processes. Natural sources of benzene which include volcanoes and forest fires, account for a small amount of benzene in the environment. Benzene is also a natural part of crude oil and gasoline. Benzene is produced primarily from petroleum sources and is used mostly in the manufacture of other chemicals used to make plastics, synthetic rubbers, fibers, and resins. Benzene is also used to make drugs, dyes, pesticides and other agricultural chemicals, lubricants, solvents, and cleaning products. Most people can begin to smell benzene in air at 1.5 to 4.5 ppm (8).
All workers at Chemfax likely were exposed, are being exposed, and will be exposed to benzene in ambient air (Table 1). The highest level of benzene in ambient air at the site (18 ppb or 57 micrograms per cubic meter (ug/m3) far exceeds levels of benzene detected in outdoor air in parts of New Jersey, California, and North Carolina. In addition, the highest level of benzene in ambient air at the site also exceeds guidelines or standards for benzene in ambient air set by the states of North Dakota (zero), North Carolina (0.12 ug/m3), Michigan (0.14 ug/m3), and Massachusetts (1.5 ug/m3). However, some other states have set higher guideline levels ranging from 72 to 300 ug/m3 (8). It is possible that the small group of workers involved in maintenance, chemical or chemical waste processing duties are those at higher risk, and might experience mild depression in their immune systems because of their exposures to high levels of benzene in ambient air.
DHHS/NTP, IARC, and the EPA regard benzene as a human carcinogen. According to IARC, many case reports and case series have described the association of leukemia with exposure to benzene, either alone or in association with other chemicals. Based on this information, ATSDR has determined that the small number of workers exposed to the highest levels of benzene in ambient air at the site might have a low increased risk of developing leukemia over a lifetime.
Carbon tetrachloride is a clear liquid that evaporates very easily; therefore it is often found in the environment in the gaseous form. Most carbon tetrachloride that escapes to the environment is found as a gas in the atmosphere. Carbon tetrachloride has a sweet odor and most people can begin to smell it in air at 10 ppm. Carbon tetrachloride does not occur naturally but has been produced in large quantities to make refrigeration fluid and propellants for aerosol cans. Since refrigerants and aerosol propellants have been found to affect the earth's ozone layer, the production of these chemicals is being phased out. Consequently, the manufacture and use of carbon tetrachloride will probably decline in the future. In the past, carbon tetrachloride was widely used as a cleaning fluid, in both industry and dry cleaning establishments, where it served as a degreasing agent. It was also used in the household to remove spots from clothing, furniture, and carpeting. Carbon tetrachloride was also used in fire extinguishers and as a fumigant to kill insects in grain. These uses were discontinued in the mid-1960s and 1986, respectively (9).
The exposure of Chemfax workers to carbon tetrachloride in air is similar to that for benzene, with maintenance and chemical/waste process workers probably exposed to higher amounts than others elsewhere on site (Tables 1 and 7). However, the worker's inhalation exposure to carbon tetrachloride is far lower than ATSDR's intermediate inhalation MRL of 0.01 ppm (9). In addition, the highest level of carbon tetrachloride reported in ambient air at Chemfax (0.14 ppb or 0.88 ug/m3) is also lower than the acceptable ambient air concentrations of carbon tetrachloride set by most of the states in the United States (9). Adverse noncarcinogenic health effects are unlikely to occur in workers exposed to low levels of carbon tetrachloride in ambient air.
DHHS/NTP, IARC, and the EPA consider carbon tetrachloride to be a carcinogen. An IARC working group reported that there were no adequate data to evaluate the carcinogenicity of carbon tetrachloride. However, three case reports described liver tumors associated with cirrhosis in humans exposed to carbon tetrachloride. One mortality study of laundry and dry cleaning workers exposed to a variety of solvents including carbon tetrachloride indicated excess respiratory cancers, liver tumors, and leukemia. Workers who are exposed to the highest level of carbon tetrachloride reported in ambient air at Chemfax are not likely to incur an increased risk of developing cancer.
Dibenzofuran is released into the environment in atmospheric emissions through burning of coal, organic matter, refuse, and diesel fuel. The chemical has also been found in tobacco smoke.
Maintenance workers likely were exposed, are being exposed, and will be exposed in the future to dibenzofuran in sediments from drainage holding ponds and ditches on site (Table 5). There is no Toxicological Profile or health guideline for dibenzofuran. However, the concentration (0.29 ppm) of dibenzofuran in the sediments is more than 10 times lower than the maximum concentration (3.6 ppm) of dibenzofuran in sediments collected in 1983 from Eagle Harbor, near Puget Sound, Washington, which had been receiving creosote effluents (10). Little is known of any human health effects as a result of long-term exposure to low concentrations of dibenzofuran. It is probable that workers in close contact with sediments containing the low levels of dibenzofuran reported are not likely to experience any adverse health effects. In addition, potential exposure to low levels of dibenzofuran found in groundwater on site (Table 2) is not likely to cause adverse health effects.
4,4-DDD or DDD (p,p'-dichlorodiphenyldichloroethane) is found in small amounts as a contaminant in technical DDT. 4,4-DDD was also used to kill pests, and one form of DDD has been used medically to treat cancer of the adrenal gland. The use of 4,4-DDD to kill pests has been banned. 4,4-DDD can also be found in the body as a breakdown product of DDT. Since 4,4-DDD is a metabolite of DDT as well as a contaminant of commercial preparations of DDT, many of the effects of DDT could be mediated through 4,4-DDD (11).
Chemfax workers likely were exposed, are being exposed, and will be exposed in the future to 4,4-DDD in surface soils through skin contact, inhalation, and ingestion (Tables 3 and 7). There are currently no MRLs or RfDs for 4,4-DDD. Since 4,4-DDD is a metabolite and a contaminant of commercial preparations of DDT, many of the effects of DDT could be mediated through 4,4-DDD. However, the estimated ingestion dose for the workers is far less than the acceptable daily intake (0.005 mg/kg) of DDT recommended the World Health Organization (WHO) or RfD (0.0005 mg/kg/day) for DDT. In addition, the estimated ingestion dose is approximately 700 million times lower than the lowest dose of 4,4-DDD that caused no adverse health effects in laboratory animals after 78 weeks of chronic/long-term studies. Noncarcinogenic health effects are unlikely to occur in workers exposed to low levels of 4,4-DDD in soils on site.
DHHS/NTP, IARC, and the EPA regard 4,4-DDD as a possible/probable human carcinogen because 4,4-DDD has caused lung/liver tumors or cancer of the thyroid in laboratory animals. Based on this information, the exposed workers are not likely to develop cancer because of their exposure to 4,4-DDD in surface soils.
Endrin ketone might be found in the environment as a breakdown product of endrin. The primary chemical, endrin, is a solid white substance that has been used as a pesticide to control insects and rodents. It is no longer produced or sold for general use in the United States. Little information is known about the properties of endrin ketone (12).
Most workers at Chemfax likely were exposed, are being exposed, and will be exposed in the future to endrin ketone in surface soils (Table 3). Maintenance workers or any construction workers who are close to surface soils are at greater risk than others. However, the estimated ingestion dose for the workers is about 7 million times lower than the doses of endrin (the primary/parent chemical) that caused enlargement of the heart or kidney in experimental dogs after 1 to 2 years of chronic/long-term studies (12). Adverse health effects are unlikely to occur in workers because of their exposure to low levels of endrin ketone in soils.
Methyl Butyl Ketone (MBK)
MBK, also known as 2-hexanone, is a clear, colorless liquid with a sharp odor. It is slightly soluble in water and can easily evaporate into the air. It is a waste product of wood pulping, coal gasification, and oil shale operations. It was formerly used in paint and paint thinner and in various chemical substances. However, since it was found to have harmful health effects, it is no longer made in the United States, and its uses have been restricted. There are no known major natural sources of MBK (13).
Workers at Chemfax who formerly used well water potentially were exposed to MBK in groundwater (Table 2), and residents off site who use well water potentially are being exposed; information is not available to confirm these exposures. However, the estimated potential ingestion doses for workers and residents, including children, are between 1,000 to 40,000 times lower than the doses of MBK that caused no adverse health effects in laboratory animals after 40 weeks of exposure (13). Workers and residents are unlikely to experience any adverse health effects because of potential exposure to MBK in groundwater. In addition, there is currently no available information on the carcinogenic potential of MBK.
Methylene chloride, also known as dichloromethane, is a colorless liquid that has a mild, sweet odor; evaporates very quickly and will not burn easily. It is widely used as an industrial solvent and as a paint stripper. It can be found in certain aerosol and pesticide products and is used to manufacture photographic film. Methylene chloride does not appear to occur naturally in the environment. It is made from methane gas or wood alcohol (14).
Chemfax workers likely have been exposed to methylene chloride in ambient air in the same manner as they have been exposed to benzene and carbon tetrachloride discussed above. However, the inhalation exposure for the workers is lower than EPA's chronic RfD of 3 mg/m3 or ATSDR's intermediate inhalation MRL of 0.03 ppm for methylene chloride. Noncarcinogenic health effects are unlikely to occur because of exposure to low levels of methylene chloride.
DHHS/NTP, IARC and the EPA consider methylene chloride to be a probable/possible carcinogen because methylene chloride administered through inhalation caused increased incidence of alveolar/bronchiolar neoplasms in laboratory mice of both sexes. According to an IARC working group, methylene chloride inhalation also increased fibroadenoma (breast tissue abnormalities) in female rats. However, the data from a study of 751 occupationally exposed workers were considered by IARC to be inadequate to assess the carcinogenicity of methylene chloride in humans. Based on this information, workers at Chemfax might have a very low or no apparent increased risk of developing breast tissue cancer over a lifetime because of exposure to the highest levels of methylene chloride reported in ambient air.
Styrene is a colorless liquid that evaporates easily and has a sweet smell. However, styrene often contains other chemicals that give it a sharp, unpleasant smell. Styrene is used mostly to make rubber and plastics. Billions of pounds of styrene are produced for this purpose each year in the United States. Products produced from styrene include packaging, insulation, fiberglass, pipes, automobile parts, drinking cups and other food-use items, and carpet backing. Styrene is also present in combustion products like cigarette smoke and automobile exhaust. Low levels of styrene occur naturally in a variety of foods, such as fruits, vegetables, nuts, beverages, and meats. Styrene can also be found in air, soil, and water after release from the manufacture, use, and disposal of styrene-based products (15).
The inhalation exposure to styrene occurring in the small group of Chemfax workers (Tables 1 and 7) exceeds ATSDR'S chronic inhalation MRL of 0.06 ppm for styrene. In addition, the highest level of styrene in ambient air at Chemfax exceeds levels of styrene detected in outdoor air in some areas of New Jersey, California, and North Carolina. It is possible that workers exposed to the highest level of styrene reported in ambient air might experience mild decrease in verbal learning skills after more than 9 years of employment.
Although IARC and the EPA consider styrene to be a possible/probable carcinogen because styrene has been shown to cause mammary tumors in laboratory rats (15), the EPA has not yet determined an inhalation unit risk for styrene. Therefore, it is difficult to determine whether any mammary tumors will occur in any exposed workers.
Workers at Chemfax, other workers at nearby businesses, and some residents within the Chemfax area likely were exposed, are being exposed, and will be exposed in the future to several metals in surface soils, sediments, and surface water (Tables 3, 5 and 6). However, the estimated ingestion doses for workers and residents, including children, do not exceed the MRLs, RfDs, RDAs, or ADIs for aluminum, calcium, copper, iron, magnesium, mercury, nickel, and sodium (Table 9). Although there are no ingestion health guidelines for cobalt, the estimated ingestion doses for workers is more than 20 million times lower than the doses of cobalt that caused less serious vomiting, nausea, edema, liver necrosis, or any serious heart muscle conditions in humans (16). In addition, the estimated ingestion doses of lead in the soils are lower than the RfD of 0.0000001 mg/kg/day for alkyl leads. Workers and residents are unlikely to suffer any adverse health effects because of exposure to low levels of metals.
Potential exposure to metals in groundwater on and off site (Table 2) could pose a public health hazard because levels of some contaminants in monitoring/industrial wells both on and off site exceed natural background levels or health guidelines. Potential exposure to contaminants in subsurface soils can be avoided if the future remedial workers or any construction workers wear protective clothing and follow prescribed guidelines.
Review of the Mississippi disease incidence and vital health statistics records for the period 1980 to 1992 did not show any abnormal incidence rates or increase in deaths due to diseases in Harrison county compared to state rates. The state cancer registry is scheduled to begin operations early in 1995. In addition, examination of data in the children's medical program records for the years 1991 to 1993 did not show any abnormal incidence rates of diseases in Harrison county compared to state rates. However, the incidence of neurological and orthopedic cases tended to be higher than other cases in all public health districts for the period 1991 to 1993. According to the director of the children's medical program, the higher reporting rate for neuorological and orthopedic cases occurs because more specialists focus on those diseases than on others.
We have addressed each of the community concerns about health as follows:
- Are health problems such as headaches, allergies, hearing disorders, memory loss,
long-term blood platelet disorder, respiratory conditions including asthma suffered by
some residents caused by exposure to site-related contaminants?
Several of the chemicals related to the site have been directly or indirectly associated with the development of practically all of the health problems listed above either in animals or in humans. However, there are not enough environmental data to enable us to determine which health effects can occur in residents living within the vicinity of the site. Therefore, ATSDR has recommended that the appropriate federal and state agencies analyze drinking water, ambient air, additional surface soil in nearby off-site areas, and surface water and fish from the Industrial Seaway and other potential routes of human exposure to contaminants in the area.
Toxicological evaluation of on-site data indicates that workers exposed to the highest levels of PAHs in soils and sediments and to benzene, methylene chloride and styrene in ambient air are likely to experience mild forms of health effects including headaches, nausea, skin irritations and decrease in immune function and verbal learning skills. However, the manifestation of these health effects would depend upon long-term continuous exposure.
- Are the cases of leukemia, breast and other cancers in the community due to exposure to site-related contaminants?
According to IARC, many case reports and case series have described the association of leukemia with exposure to benzene, either alone or in association with other chemicals. According to an IARC working group, methylene chloride inhalation has caused increased mammary tumors in female rats and lung cancer in mice of both sexes. However, another working group of IARC, which reviewed data of occupationally exposed workers, considered the data inadequate to assess the carcinogenicity of methylene chloride in humans. ATSDR reviewed the Mississippi disease incidence and vital health statistics records for the period 1980 to 1992. There were no abnormal increases in deaths due to cancer in Harrison county compared to state rates. The state cancer registry is scheduled to begin operations early in 1995. There are not adequate environmental data to enable us to determine whether exposure to any contaminants in private well water, residential soils, surface water and fish from the Industrial Seaway can result in excess cancer. When pertinent environmental data are available, ATSDR will evaluate the data for cancer and reevaluate the community concerns about cancer.
However, toxicological evaluation of soil, sediment and ambient air data indicates that exposed workers might have: 1) a low chance of developing additional stomach, laryngeal or esophageal cancer due to high PAHs in soils and sediments; 2) a low chance of developing additional leukemia because of high concentrations of benzene in air; and 3) a low or no apparent risk of developing lung or mammary tumors from high levels of methylene chloride in air.
- Is it safe to swim and fish in the Industrial Seaway and other surface water elsewhere?
Data are not available for Seaway water or fish to determine whether contamination is present and what, if any, health effects any contaminants might cause for persons who swim or eat fish caught there. Therefore, ATSDR is recommending sampling of Seaway media. ATSDR does not believe other area surface waters are pertinent to this assessment, except for the ponds and ditches specifically associated with the site, and swimming and fishing in those waters is not feasible.
- Does the intermittent chemical odor in residential, school, and shopping areas cause discomfort and other health effects?
Quite a few people from the area reported a range of physical discomforts associated with the odors experienced from area industries. Several studies conducted in the U.S. and in overseas countries indicate that noxious environmental/chemical odors might trigger symptoms by a variety of physiological mechanisms, including exacerbation of underlying medical conditions, stress-induced illness, and increase in the occurrence of health effects including headaches, nausea, and eye and throat irritations. In addition, the severity of such health effects might depend upon the type and amount of the chemical present in the air or environment. However, the reasons for these associations cannot be explained solely by scientific research. ATSDR is recommending off-site ambient air sampling.