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PUBLIC HEALTH ASSESSMENT

MCCLELLAN AIR FORCE BASE
SACRAMENTO, SACRAMENTO COUNTY, CALIFORNIA


PUBLIC HEALTH IMPLICATIONS

A. Toxicological Evaluation

In this section, ATSDR discusses health effects that may result from exposures to site contaminants. People can only be exposed to a site contaminant if they come in contact with it. Exposure can occur by breathing, eating, or drinking the contaminant, or by dermal (skin) contact with contaminated water, soil, or air.

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

To determine the possible health effects of a variety of chemicals, ATSDR researched the scientific literature. The resulting information was compiled and published in a number of chemical-specific ATSDR documents called Toxicological Profiles. Toxicological Profiles are references that list health effects that could result from exposure to a specific chemical in the environment.

Toxicological Profiles include health guidelines such as ATSDR's Minimal Risk Level (MRL), EPA's Reference Dose (RfD), Reference Concentration (RfC), and Cancer Slope Factors (CSF). Health guidelines provide a basis for comparing estimated exposures with concentrations of contaminants in different environmental media (soil, air, water, and food) to which populations may be exposed. ATSDR's MRL is an estimate of daily human exposure to a chemical likely to be without appreciable risk of deleterious effects (noncancer) over a specified duration of exposure. MRLs are derived from studies in people and animals and are reported for acute (14 days or fewer), intermediate (15-364 days), and chronic (365 days or longer) exposures. If an individual's daily exposure is below the MRL, adverse health effects are not expected. An RfD is EPA's estimate of the daily exposure (by the oral route) of the human population, including sensitive subpopulations, likely to be without appreciable risk of deleterious effects during a lifetime (70 years). An RfC is EPA's estimate of the concentration of a contaminant in air to which daily exposure (by inhalation) of the human population, including sensitive subpopulations, is likely to be without appreciable risk of deleterious effects during a lifetime (70 years).

Comparison values such as RfDs and RfCs do not consider, however, the risk of developing cancer. For carcinogenic chemicals, EPA established cancer slope factors that define the relationship between doses and the likelihood of an increased risk of cancer in exposed individuals compared with non-exposed control individuals. EPA has calculated cancer slope factors for ingestion and inhalation exposures.

The profiles include the Environmental Protection Agency's (EPA) weight-of evidence classification for carcinogens, which define a specific chemical's ability to cause cancer in humans and animals. According to EPA, Class A chemicals are known human carcinogens, and Class B chemicals are probable human carcinogens. Class B is further subdivided into two groups: Group B1 consists of chemicals for which there is limited evidence of carcinogenicity from epidemiologic studies in humans; and Group B2 consists of chemicals for which there is sufficient evidence of carcinogenicity in animals, but inadequate evidence or no data available from epidemiologic studies in humans. Group C chemicals are possible human carcinogens and Group D chemicals are not classifiable as to human carcinogenicity.

Other comparison values, such as the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs), and NIOSH Recommended Exposure Limits (RELs) are used to provide safe and healthful working conditions for working men and women. PELs are designed to ensure, to the extent feasible, that no employee suffers impairment of health or functional capacity even if he/she is regularly exposed to a toxic material throughout working life. PELs are usually listed as 8-hour time-weighted averages (TWA). It is important to understand that PELs apply only to healthy employees working 40-hour weeks, and do not apply to the general population (including children, the elderly, and the sick), which may be subject to continuous environmental exposure.

NIOSH RELs are used in combination with engineering and work practice controls, exposure and medical monitoring, labeling, posting, worker training, and personal protective equipment to protect worker health and safety over a working lifetime. The REL is frequently expressed as a TWA for up to a 10-hour day during a 40-hour week. It may also be expressed as (a) a short-term exposure limit (STEL), a 15-minute, time-weighted average exposure that should not be exceeded at any time during a workday, or (b) a ceiling limit -- a concentration -- that should never be exceeded -- even for an instant -- at any time during a workday. NIOSH has identified numerous chemicals that should be treated as occupational carcinogens even though OSHA has not identified them as such.

Using the available health guidelines and scientific information, ATSDR determines the likelihood that an adverse health effect, cancerous and/or noncancerous, will occur as a result of exposure to contamination. Cancerous and noncancerous health effects occur via different biological mechanisms, and therefore, are evaluated separately using different health guidelines and scientific information. If either cancerous or noncancerous health outcomes are expected to occur as a result of exposure to contaminants, the exposure is determined to be of public health concern.

ATSDR's quantitative evaluation of human exposure by water and soil ingestion and by inhalation uses media-specific rates for adults and children (see Appendix C). The rates are calculated by multiplying the contaminant concentration by the ingestion rate for an adult or a child, and then dividing that number by the appropriate standard body weight (70 kg for adults, 10 kg for a child). The water ingestion rates used for adults and children are 2.0 liters/day and 1.0 liter/day, respectively. For soil and sediment, the ingestion rates used are 100 mg/day for adults, 500 mg/day for school-age children, and 5,000 mg/day for pica children (children who ingest soil in amounts far exceeding those observed in the average child). ATSDR uses an inhalation rate of 23 cubic meters (m3)/day for adults and 3.8 m3/day for a 1-year-old child. Some exposures are intermittent or irregularly timed. For those exposures, an exposure factor (EF) is calculated that averages the dose over the exposure period.

Individuals on and off the McClellan Air Force Base site may have been exposed to multiple chemicals in the water, soil, sediment, and air. ATSDR recognizes that exposure to multiple contaminants may modify the resulting toxicity from chemical exposure. However, data are very limited on the health effects of multiple chemical or multiple route exposures. Toxicity from exposure to two or more chemicals may be additive (equal to the sum of the toxicity from individual chemicals), synergistic (greater than the sum of the toxicity from the individual chemicals), or antagonistic (less than the sum of the toxicity from the individual chemicals). Therefore unless scientific information concerning multiple chemical exposure is available, ATSDR evaluates individual contaminant exposure.

On Site

ATSDR has identified three completed exposure pathways for on-site military and civilian populations: past exposure via ingestion of TCE-contaminated water from the base's water production wells; inhalation of ambient air (past, current, and future) contaminated with TCE, PCE, 1,1-DCE, MC, benzene, and mercury; and ingestion of PCB-contaminated surface soil (past, current, and future).

Off Site

Three completed exposure pathways for off-site residents were identified by ATSDR: private wells, ambient air, and sediment (Magpie Creek). Contaminants detected in off-site residential water wells that are above health comparison values and in a past completed exposure pathway include TCE, 1,1-DCE, MC, VC, cadmium, arsenic, 1,2-DCA, and PCE. The ambient air pathway section discusses the following contaminants: TCE, 1,1-DCE, PCE, MC, 1,1,1-TCA, and benzene. People have been exposed in the past and are still being exposed to contaminants in the air. Off-site sampling of sediment from Magpie Creek identified cadmium, and lead as contaminants of concern. People were exposed to those contaminants in the past and are still being exposed.

Results of off-site air monitoring on the perimeter of OU D and at four off-site residential yards indicate air contamination. Ambient air in the crawl spaces of some off-site homes is an occasional completed exposure pathway (i.e., only occurring if someone works or plays in the area). Air sampling in the crawl spaces indicates VOCs from the soil have volatilized; further sampling of ambient air in the breathing zones of the homes is needed to assess occupant exposure.

Trichloroethene (TCE)

On-site residents, civilian and military personnel, and off-site residents living west on the base have been exposed to TCE in groundwater and ambient air. On- and off-site exposure at McClellan Air Force Base resulted from long-term (more than a year) ingestion of contaminated water from base and private residential wells. Other domestic uses of water (e.g., cooking and bathing) resulted in residents inhaling TCE volatilized from the contaminated water and dermal absorption of TCE from the contaminated water. Limited air monitoring data indicate that on- and off-site military and civilian populations near OU B and OU D were also exposed to TCE by the inhalation route.

EPA assigned a B2 classification (probable human carcinogen by oral and inhalation routes) to trichloroethylene based on animal studies. In 1988, the Scientific Advisory Board for the EPA offered an opinion that the weight-of evidence was on a C-B2 continuum (possible-probable human carcinogen). The classification status is currently under review. TCE is not classifiable for cancer according to National Toxicology Program and the International Agency for Research on Cancer (50). To be most protective to the public, ATSDR used the more conservative classification and EPA's cancer slope factor for evaluation of exposures to TCE at McAFB.

The maximum concentration of TCE (22.5 µg/L) was detected on-site in Building 368, a distribution point for on-site base potable water. The range of TCE detected in other distribution points sampled was < 0.5 - 22.2 µg/L (Table 1-B). Samples containing those concentrations were collected in 1979-80; the wells that contributed to the contamination were taken off line in 1980. When they were active, the wells supplied water to the entire base; therefore, on-site military and civilian populations were exposed in the past to TCE in the base water supply. How long people were exposed to TCE before sampling took place is not known. Definitive TCE exposure is documented during the 12- to 13-month period before the wells were taken off line (12).

Using a worst case scenario, on-site TCE exposure by ingestion during that time frame would not be expected to result in an increased cancer risk and is not of public health concern. The dose estimations for adults and children did not exceed the intermediate MRL of 0.7 mg/kg/day. Therefore, adverse, noncancer health effects are not expected from exposures of one year or less duration. Reports in the literature indicate that, while showering, people generally inhale an amount of VOCs equivalent to that found in 2 liters of water (51). Therefore, if the estimated TCE inhalation and ingestion exposures at McAFB are additive, they do not exceed the ATSDR oral intermediate MRL of 0.7 mg/kg/day. Dermal exposure would not increase the total exposure sufficiently to be of public health concern.

A health guideline for chronic TCE exposure has not been developed. Little information is available about adverse health effects in people following chronic TCE exposure. However, exposure to TCE on-site at McAFB would be unlikely to exceed exposures that have been reported to result in adverse noncancer health effects in animals. Exposures in animal studies are thousands of times greater that the expected exposures of people on-site at McAFB. Therefore, it is unlikely that chronic exposures to contaminated water would result in adverse noncancer health effects.

Off-site residents living west of the base have also been exposed in the past to TCE in private well water by way of inhalation, ingestion, and dermal absorption. Off-site residential well samples collected in 1986 had a maximum TCE concentration of 55.0 µg/L. Estimated past exposures from ingestion (0.0015 mg/kg/day for adults and 0.006 mg/kg/day for children) to TCE are not of public health concern and are less than the oral intermediate MRL of 0.7 mg/kg/day. A chronic health guideline is not available for TCE. However, total chronic exposures from inhalation of volatilized TCE and from dermal contact with water is not expected to result in total chronic exposure of public health concern. Therefore, adverse noncancer health effects are not expected in the exposed population. However, based on EPA's cancer slope factor these past exposures may be of public health concern in regard to cancer risk. In the area of concern, approximately 20 of 240 private wells sampled had concentrations of VOCs that were of public health concern.

Municipal water was provided to the area in 1986. Therefore, current exposure would occur only if residents have continued to use the contaminated private wells. Exposure may occur if residents have continued to use the private wells for potable purposes or if they water lawns or gardens (inhalation of volatilized TCE). ATSDR received limited private well sampling data in 1991; levels of TCE were identified at 4.10 µg/L. The estimated exposure doses of 0.0001 mg/kg/day for adults and 0.0004 mg/kg/day for children do not exceed the intermediate MRL. Therefore, exposure of residents to these concentrations is not of public health concern for adverse noncancer health effects. The concentrations are also not of public health concern for cancerous health effects.

On- and off-site military and civilian personnel and residents west of the base have also been exposed to TCE in ambient air by way of inhalation. Annual average air monitoring sampling data in 1987 identified TCE at 0.05 parts per billion volume (ppbv) at Station 2 (near off-site residents). Data for Station 5 (OU B) include only the fourth quarter average, which identifies TCE at 0.20 ppbv. In 1992, ATSDR received air monitoring data for Station 2 and the Groundwater Treatment Plant (GWTP). TCE levels of 2.1 ppbv and 0.087 ppbv, respectively, were detected. The intermediate EMEG for TCE is 2000 ppb. Concentrations that people are exposed to are several thousand-fold less than the EMEG. Therefore, noncancer health effects are not expected from these exposures. The CREG for TCE in air is 0.06 µg/m3 (0.01 ppb). Therefore, exposures to TCE in ambient air may be of public health for cancerous health effects.

People particularly susceptible to TCE exposures are chronic consumers of alcohol, people with heart disease, people taking disulfiram (a medication used to treat alcoholism), and people taking the anticoagulant warfarin (50). Those medications increase the toxicity of TCE in the liver by interfering with its normal metabolism.

1,2-Dichloroethane (1,2-DCA)

Off-site residents were exposed to 1,2-DCA in contaminated groundwater by way of inhalation, ingestion, and dermal absorption. Automobile and heavy equipment mechanics, machinists, and registered nurses are frequently exposed to 1,2-DCA in the workplace (52). The National Occupational Exposure Survey conducted by NIOSH notes that occupational exposure to 1,2-DCA occurs when it is used as a fumigant, solvent, or diluent in open-system operations (52).

EPA has classified 1,2-DCA as a B2 probable human carcinogen by the oral and inhalation routes because of evidence of its carcinogenicity in animals and because data from studies in people are inadequate (52). The maximum concentration of 85.0 µg/L was found in 1986 in off-base residential wells. From the levels detected, estimated exposure doses indicate that off-site sensitive populations (children) have an increased risk of developing cancer, and their exposures are of public health concern.

Off-base residents were exposed to 1,2-DCA in the past when they inhaled it during bathing and cooking, when it would be likely to volatilize. Reports in the literature suggest that inhalation exposure during those activities is equal to exposure from ingestion (51). Because residences have been supplied with municipal water since 1986, residents currently would be exposed to 1,2-DCA only if they used private well water to water their lawns or gardens or if they drank the contaminated water. New sampling data (1991) from six off-site residential wells found a 1,2-DCA level of 0.70 µg/L. Inhalation or ingestion of that or similar levels does not increase the risk of developing cancer.

The health effects of long-term exposure to drinking water contaminated with 1,2-DCA are not known (52). Until more data are available, we are unable to determine whether health effects are likely to occur in off-site residents who had 1,2-DCA in their wells. Data on noncancer human health effects associated with 1,2-DCA exposures are very limited and have been documented from case reports of accidental or intentional ingestion of high concentrations of pure 1,2-DCA. Such exposures have resulted in depression, nausea, vomiting, diarrhea, gastritis, colitis, hepatic damage and cirrhosis, congestion in the lungs, pulmonary edema, and bronchitis (52).

Persons taking disulfiram or phenobarbital are highly sensitive to the effects of 1,2-DCA (52). Reduced nutritional intake, such as fasting, may also increase the toxicity of 1,2-DCA (52). Liver enzymes are largely responsible for the metabolism of chemicals like 1,2-DCA. Both, reduced nutritional intake and chemicals like disulfiram and phenobarbital, have the ability to alter enzyme levels in the liver. These liver enzyme alterations may result in increased toxicity by changing the metabolism of 1,2-DCA.

Methylene Chloride (MC)

On-site military and civilian populations and off-site residents west of the base have been and are currently exposed to methylene chloride (MC) in ambient air. Off-base residents were also exposed to MC in the past by way of chronic ingestion and inhalation of and dermal contact with private well water. Because off-site residences have been supplied with municipal water since 1986, residents currently should only be exposed if they have continued to use contaminated private wells. However, the number of residential wells currently in use and whether or not they are used for drinking water or irrigation is not known.

Methylene chloride is widely used as an industrial solvent and as a paint stripper (53). It can also be found in certain aerosol and pesticide products and in the manufacture of photographic film. Methylene chloride does not occur naturally in the environment and is usually released to the environment in air and to a lesser extent in water and soil, as a result of industrial and consumer uses (53). EPA has classified MC as a B2 probable human carcinogen by the oral and inhalation routes (53).

In 1987, the maximum concentrations of MC found in ambient air at Stations 2 and 5 were 1.38 ppbv and 7.52 ppbv, respectively. Exposures to those levels would not be expected to result in an increased cancer risk and are not of public health concern. The maximum concentrations detected do not exceed the intermediate inhalation MRL of 2000 ppb; therefore, adverse noncancer effects are unlikely. The dose estimations for Station 2 and 5 are 0.002 and 0.026 mg/kg/day, respectively.

Air monitoring data received by ATSDR in 1992 indicate MC at a level of 1.5 ppbv at Station 2 (near residents' homes) and at 0.31 ppbv in the yards of residents off base. A concentration of 1.75 ppbv was measured at the Groundwater Treatment Plant, another air station on base. These concentrations are lower than levels detected in 1987. Exposures to these concentrations are not of public health concern and are not expected to result in adverse health effects.

The maximum concentration of MC found in private, off-site, residential water wells was 96.2 µg/L, a level at which there would be no apparent increased risk of developing cancer if the contaminated water was ingested over 70 years. Therefore, those exposures are not of public health concern. The estimated exposure doses do not exceed the chronic oral MRL of 0.06 mg/kg/day; therefore, adverse noncancer health effects would not be expected.

The effects of long-term oral exposure to MC have been studied only in animals. There is no information on long-term oral exposure in people (53). Impairment of the central nervous system and decreased visual and auditory functions are the major manifestations associated with short-term human exposure by way of inhalation at concentrations 42,000 times higher than the concentrations at McAFB (53). There is little information in the literature on adverse noncancer health effects associated with concentrations found at McAFB.

Methylene chloride changes to carbon monoxide in the liver, resulting in a condition known as carboxyhemoglobinemia. The condition develops because carbon monoxide interferes with normal oxygen transport in the blood. Several populations may be especially sensitive to MC (54). Persons with preexisting coronary artery disease or respiratory dysfunction and smokers may experience adverse health effects at lower levels than healthy people. Published research studies have demonstrated that exposure to MC may be of health concern to pregnant women because it readily crosses the placenta (53).

Vinyl Chloride (VC)

Off-site residents have been exposed in the past to vinyl chloride (VC) in private well water by way of inhalation, ingestion, and dermal absorption. After residents' homes were connected to municipal water in 1986, exposures to VC would have occurred only if residents continued to use the contaminated private wells..

According to the literature, people typically exposed to VC include those who live on or near landfills where VC was disposed, and those exposed to it as a degradation product of TCE, PCE, or 1,1,1-trichloroethane (55). Vinyl chloride is used almost exclusively in the United States by the plastics industry for the production of polyvinyl chloride (PVC). PVC is used to make a variety of plastic products, including pipes, wire and cable coatings, and packaging materials (55). EPA has classified VC as a Class A known human carcinogen by the oral and inhalation routes (55).

The maximum concentration of vinyl chloride in residential water wells near McAFB was 17.3 µg/L (detected in 1983). Exposure to that concentration by way of ingestion may result in an increased risk of developing cancer. The estimated exposure doses also exceed the chronic oral MRL of 0.00002 mg/kg/day. Therefore, past exposure to the levels detected in 1983 were of public health concern.

In 1992, ATSDR received limited residential well data pertaining to six off-site wells; the wells had levels of vinyl chloride below 0.2 µg/L. Exposures to those concentrations do not exceed the chronic oral MRL.

There are no reports in the literature of health effects associated with chronic, low-level exposure to VC by ingestion or inhalation. Studies of occupational exposure have identified two primary target organs of vinyl chloride toxicity: the liver and the central nervous system (55). Other health effects include fatigue, damage to the lungs, and poor circulation (55). Exposure to VC is known to result in angiosarcoma, a rare malignant cancer of the blood vessels that normally occurs in the skin and breast. VC exposure in people, however, has caused angiosarcoma of the liver (55).

In addition to VC exposure by way of ingestion, off-site residents may inhale VC when using water for domestic purposes, such as bathing, cooking, and watering lawns and gardens. It has been estimated that inhalation exposures are equivalent to those by ingestion (51). Residents may inhale VC if it is present in the crawl spaces of their homes (off-site residences).

Tetrachloroethene (PCE)

On- and off-site military and civilian residents have been and are being exposed to PCE in ambient air by way of inhalation. Off-site residents were exposed to PCE in contaminated groundwater by way of inhalation, ingestion, and dermal absorption until 1986. Off-site residents currently may be exposed to PCE migrating in groundwater from McAFB if they have continued to use contaminated wells.

PCE is a synthetic substance used widely for dry cleaning fabrics and in textiles and metal-degreasing operations (56). People are exposed from environmental, consumer product, and occupational sources. EPA has classified PCE as a B2 probable human carcinogen by the oral and inhalation routes because of evidence of its carcinogenicity in animal studies (56). Current information is insufficient to determine whether PCE causes cancer in people. The maximum concentrations of PCE found in ambient air at stations 2 and 5 were 0.21 ppbv and 0.25 ppbv. Inhalation of those levels does not increase the risk of developing cancer and is not of public health concern. The concentrations also do not exceed the intermediate inhalation MRL of 9 ppbv, and are not expected to result in noncancer adverse health effects.

Air monitoring data received by ATSDR in 1992 indicate a level of 4.64 ppbv PCE at Station 2 (near residents' homes). Data from the Groundwater Treatment Plant indicate a concentration of 0.29 ppbv. In addition, the new data indicate a maximum level of 0.31 ppbv from yards of residents off base. Exposure estimations for adults and children calculated from those concentrations are not of public health concern, and exposed individuals are not expected to have adverse health effects.

The maximum concentration of PCE found in off-base residential water wells was 4.0 µg/L. Ingestion of that level does not increase the risk of developing cancer and is not of public health concern. The estimated doses do not exceed the intermediate ingestion MRL of 0.1 mg/kg/day or the chronic RfD of 0.01 mg/kg/day. Noncancer adverse health effects are not likely to be caused by such exposures. Off-site residents near Station 2 may have been exposed in the past to PCE by way of inhalation during use of contaminated water for domestic purposes and/or irrigation, and by the ambient air pathway. Simultaneous exposure to multiple routes by way of inhalation and ingestion may result in an increased exposure for those individuals. The multiple route exposures to PCE are not expected to be of public health concern.

Research studies have demonstrated that exposure to PCE may be of health concern to pregnant and nursing women because PCE crosses the placenta and has been found in breast milk (57). Therefore, fetuses and nursing babies may be at increased risk of adverse health effects from maternal exposure (57).

Arsenic

Off-site residents were exposed to arsenic by way of ingestion, and dermal contact with contaminated water until they were provided with municipal water in 1986. Current exposure to arsenic may occur if people eat vegetables from gardens watered with contaminated groundwater and intentionally drink the private well water.

EPA has classified arsenic as a Class A known human carcinogen by the oral and inhalation routes (58). Arsenic is an element that occurs naturally in groundwater as a result of releases from volcanoes or erosion from mineral deposits, but releases from human activities and industry can lead to substantial contamination (58). Concentrations in water are usually less than 10 µg/L, although higher values can occur near natural mineral deposits or synthetic sources. From a review of arsenic data from water supply and surface water environments, Ferguson and Gavis (1972) and EPA (1991) have concluded that arsenic concentrations in natural waters often approach or exceed the limits specified in Drinking Water Standards (59,60). EPA's current Drinking Water Standards list the recommended limit for arsenic at 50 µg/L (60). EPA is currently revising its guidelines for drinking water, however, as a result of a study in Taiwan of "Cancer Risks From Arsenic in Drinking Water." That study showed a high correlation between arsenic ingestion and cancer and has affected the development of new guidelines. Following its review of pertinent data, EPA has proposed lowering the current arsenic MCL of 50 to an MCLG of zero. That decision may be announced by 1993 (60).

In 1986, the maximum concentration of arsenic found in off-site residential water wells was 6.0 µg/L. Sampling data (1991) from six off-site residential wells identified arsenic at 4.80 µg/L. Whether the source of the arsenic levels in the wells is naturally occurring or a result of contamination at McAFB is not known because background concentrations at McAFB have not been established. Residences have been supplied with municipal water since 1986. However, past exposure by way of ingestion to these concentrations could increase an individual's risk of developing cancer. The estimated exposure (0.0001 mg/kg/day) by ingestion is less than the chronic oral RfD of 0.0003 mg/kg/day. Therefore, past exposures are of public health concern only for cancerous effects.

It is important to note that if the contaminated water is used for watering vegetable gardens and/or irrigating crops, those plants could accumulate arsenic by root uptake from the soil or by absorption of airborne arsenic deposited on leaves (58). The concentration of arsenic that the plants could accumulate would depend on the type of vegetation; however, the uptake can be substantial. Therefore, at McAFB, food chain sources of arsenic are of concern if off-site residents water their vegetable gardens with arsenic-contaminated water.

Adverse health effects most likely to result from chronic oral exposure to arsenic in the range of 0.01 to 0.1 mg/kg/day include gastrointestinal irritation, peripheral neuropathy, vascular lesions, anemia, skin diseases, and skin cancer (58). These concentrations are much higher than the estimated dose of 0.0001 mg/kg/day for populations near McAFB.

Some populations may be particularly susceptible to the toxic effects of arsenic. Individuals with protein-poor diets, or a deficiency of choline (deficiency in a B-complex vitamin essential to liver function), may be especially sensitive to arsenic exposure. Also, individual genetic variability involving the liver's ability to detoxify arsenic could predispose an individual to its adverse effects (58).

Mercury, Inorganic

On-site civilian personnel in Building 252 have been exposed to inorganic mercury in ambient air by way of inhalation. The type of mercury was not specified (61). Mercury on base is probably inorganic and a result of volatilization of metallic mercury.

Mercury is a chemical that occurs naturally in the environment in several forms elemental (metallic), organic and inorganic (62). Metallic mercury is mined and is also a waste product of gold mining. Thermometers, barometers, batteries, and tooth fillings all contain metallic mercury. Inorganic mercury compounds are commonly used in electrical equipment (batteries and lamps) and fungicides (62). EPA classifies mercury as a Group D chemical, the classification assigned to agents for which there are inadequate data to evaluate human carcinogenicity.

The maximum concentration of mercury in air inside Building 252 (in the breathing zone) was 9.0 µg/m3. Exposure of civilian workers to that concentration exceeds the chronic inhalation MRL (0.3 µg/m3) for metallic mercury. Both OSHA (PEL) and NIOSH (REL) limit occupational exposure to mercury to 50 µg/m3.

The specific types of health effects that employees assigned to Building 252 could have experienced cannot be predicted because the duration of their exposures is unknown. The following health effects from exposure to mercury have been reported in the medical/scientific literature. Chronic exposure by way of inhalation to 22.0-28.0 µg/m3 of inorganic mercury for 7-25 weeks caused erethism (a psychic disturbance characterized by a peculiar form of timidity), tremors, insomnia, and nervousness (62). Poor concentration, short-term memory deficits, and deficits in psychomotor skills (e.g., finger tapping and eye-hand coordination) have also been noted following long-term, low-level occupational exposure to similar levels of inorganic mercury for an average of 15.3 years (62). Chronic mercury exposure can also damage the kidneys. Peripheral nerve damage has been documented by electromyography (EMG), a test that produces a visual record of electrical activity associated with functioning skeletal muscle. EMG is used to diagnose neuromuscular disorders. Occupationally exposed persons experience stress, sensory loss, and diminished sensation and reflexes. Workers exposed to "high" concentrations for 60-80 hours a week, 7 days a week have developed incapacitating pain of the lower back and extremities, muscle cramps, and twitching (62).

Cadmium

Off-site residents were exposed to cadmium by way of ingestion of and dermal contact with contaminated water from private wells. Residents were provided municipal water in 1986. Therefore, current exposure to cadmium in the groundwater may occur only if people have continued to use the contaminated private wells. Off-site residents have in addition been exposed and are currently being exposed to cadmium by ingestion of and dermal contact with contaminated sediment at Magpie Creek.

Cadmium is an element that occurs naturally in the earth's crust (63). Most cadmium used in this country is extracted during the production of other metals such as zinc, lead, or copper. It also has many uses in industry and consumer products, mainly batteries, pigments, metal coatings, and plastics (49). EPA has classified cadmium as a Class B1 probable human carcinogen by the inhalation route (49).

In 1986, the maximum concentration of cadmium detected in residential wells was 42 µg/L. Estimated ingestion exposure doses are 0.001 mg/kg/day for adults and 0.004 mg/kg/day for children, respectively. Those estimates exceed the chronic MRL (0.0002 mg/kg/day). Therefore, adverse noncancer health effects may occur as a result of these exposures.

Sampling results from six residential wells were presented to ATSDR in 1991; the maximum level of cadmium detected was 0.97 µg/L. Estimated exposures for adults or children to the 1991 concentration do not exceed the chronic MRL. Therefore, adverse noncancer health effects are not expected as a result of exposure to water contaminated at these concentrations.

Research studies have shown that cadmium can enter the blood following ingestion of contaminated food or water and inhalation of contaminant fumes, dusts, and aerosols (49). For the general public, food is the primary source of exposure to cadmium. Meat, fish, and fruits may contain 1-50 µg/kg of cadmium, grains 10-150 µg/kg; the greatest concentrations are found in the livers and kidneys of animals. Game birds may contain cadmium. Shellfish, which readily accumulate cadmium, are also a major dietary source. Of all metals, including lead, cadmium is most readily taken up by plants (49,64).

At McAFB, food chain sources of cadmium are of concern for off-site residents who may water their vegetable gardens and livestock with cadmium-contaminated water. Due to lack of biota sampling, this potential pathway cannot be evaluated.

Children who have played in Magpie Creek have been exposed to cadmium by incidental ingestion of and dermal contact with contaminated sediment. The maximum concentration of cadmium found in off-site sediment was 18.0 mg/kg. Estimated exposures to cadmium of school-age children (older than 6 yrs and weighing 35 kg and ingesting 500 mg/day) and pica children (ages 1-6, weighing 10 kg and ingesting 5000 mg/day) who incidentally ingested sediment from Magpie Creek more than five times a week exceed the chronic oral MRL (0.0002 mg/kg/day). Therefore, exposure to those levels may result in an increased risk of developing adverse noncancer health effects. If the exposure frequency to sediment is 3 times a week, the estimated exposure dose for pica children would still exceed the chronic MRL, at which adverse health effects may occur.

Studies reported in scientific literature indicate that once cadmium enters the body, it is retained strongly and tends to accumulate in the liver and kidney (49). Of greatest concern is low-level (less than 40 µg/kg), chronic oral exposure to cadmium; it can cause kidney damage and formation of kidney stones. The relative severity of the effects of chronic cadmium inhalation on tissues depends primarily on the intensity of the exposure. Low levels (less than 0.5 mg/m3 over 8 hours) are most likely to cause renal injury without marked lung injury; higher levels (greater than 1.0 mg/m3) could damage the lungs before renal effects develop (36). Other tissues reported as sites of injury, either in animals or people, include the liver, testes, immune system, nervous system, and blood (49). No information was found on dermal absorption of cadmium in people.

Populations sensitive to cadmium are people with previous liver or kidney damage and people with dietary deficiencies (e.g., calcium, iron, and protein). Diets deficient in calcium stimulate the synthesis of calcium-binding protein, which enhances cadmium absorption. Women with low serum ferritin levels (a protein in the blood that transports iron) have been shown to absorb twice as much cadmium as women with normal serum ferritin levels (49).

Lead

Lead was detected at a maximum concentration of 100 mg/kg in sediment at Magpie Creek. Children playing in the creek have been exposed to lead by incidental ingestion and dermal contact with contaminated sediment.

Estimated exposure doses range from 0.007 mg/kg/day (one time a week) to a daily dose of 0.050 mg/kg/day for a pica child ingesting 5000 mg of soil/sediment per day. Children 6 years of age and older weighing 35 kg who ingest 500 mg/day have estimated exposure doses ranging from 0.0002 to 0.001 mg/kg/day at an exposure frequency of one time a week to daily. Children's exposure to lead by dermal contact is insignificant because lead is not absorbed well by the skin.

Numerous research studies have indicated exposures to lead result in blood lead concentrations at which adverse noncancer health effects occur. Many studies have tried to correlate specific concentrations of lead in contaminated soils with blood lead levels in children. One of those studies, "Lead in Soil: Recommended Maximum Permissible Levels" published in 1989, has resulted in the development of permissible levels of lead in soil using the relationship between lead levels in soil and blood lead levels in children (64). An acceptable level of 600 mg/kg of lead in soil is suggested as a "safe" level and would contribute no more than 5 µg/dl to the total blood lead in children under 12 years of age (64). A maximum permissible level of 250 mg/kg in soil is recommended in areas without grass cover that are repeatedly used by children under 5 years of age (who frequently "mouth" objects). Exposure to soil contaminated at that level would add, at the most, about 2 µg/dl to the blood lead level of children (64). Concentrations of lead at Magpie Creek are two to six times lower than the levels in the 1989 study and would most likely result in minimal exposure.

EPA has classified lead as a B2 carcinogen -- a probable human carcinogen by the oral and inhalation routes (65).

Off-site residents were exposed in the past to lead by way of ingestion and dermal contact with contaminated water from private wells. Because those residents have been provided municipal water in 1986, current exposures to lead in groundwater may occur only if people continue to drink the contaminated water, and/or eat vegetables from gardens watered with contaminated groundwater.

Sampling data from six off-site residential wells was presented to ATSDR in 1991; the maximum level of lead detected was 6.00 µg/L. The estimated exposures of adults and children, if people have continued to use the wells, are 0.0002 mg/kg/day and 0.0006 mg/kg/day, respectively. Assuming the exposed children's blood lead levels are normal (3 - 8 µg/dl), no significant increases should occur from ingesting the concentrations found in private wells.

If the contaminated water is used for watering vegetable gardens and irrigating crops, plants may accumulate lead by root uptake from the soil or by absorption of airborne lead deposited on leaf surfaces (65). The concentration accumulated by the plants will depend on the type of vegetation. Therefore, at McAFB, food chain sources of lead may be of concern if off-site residents water their vegetable gardens with lead-contaminated water.

Because lead is a natural element in the environment, additional exposure to children by ingestion (of sediment, water, and vegetables) could increase the baseline blood lead concentration in children to levels greater than 10 µg/dl. In 1991, CDC/ATSDR established a new lead intervention level at 10 µg/dl; therefore, those exposures may be of public health concern.

Lead toxicity greatly depends on route of exposure and amount absorbed. In people, absorption of lead from contaminated water, soil, or from foods that are ingested appears to be low. However, gastrointestinal absorption depends on age; absorption is approximately 50% in children and 15% in adults. Therefore, the vulnerability of children ages 1 to 5 to soil lead is increased because of their hand-to-mouth and pica (ingestion of dirt) activities and their high rate of intestinal absorption. Dermal absorption of inorganic lead compounds is much less significant than absorption by inhalation or ingestion (65).

Other factors that affect the levels of lead required to produce toxic health effects are nutritional well being and adequate dietary levels of iron, calcium, and zinc. Absence of nutritional well being and nutrient deficiencies in an exposed child will result in enhanced absorption of lead and increased toxicity.

Frequent incidental exposures to lead can result in chronic toxicity because lead tends to accumulate in body tissues, especially bone (65). It is that total body burden of lead that is related to toxicity.

The most sensitive target organ of lead poisoning is the nervous system. Neurologic deficits caused by lead may be irreversible. The developing nervous system in children can be adversely affected at blood lead levels of less than 10 µg/dl. Effects of lead exposure in children include deficits in IQ score, cognitive function, psychometric intelligence scores, speech and language processing, attention span, hearing acuity, motor skills, reaction time, and hand-eye coordination (65). Anemia is not an early effect of lead poisoning and is evident only after prolonged periods of significantly elevated blood lead concentrations.

Lead toxicity may be affected by interactions with essential elements and nutrients and other metals. Those interactions may result in health effects that are additive, multiplied, or reduced. Chemicals that have been reported to interact with lead include calcium, iron, copper, cadmium, zinc, mercury, vitamin D, ethanol, and phenylhydrazine (65).

Segments of the population at highest risk of the effects of lead exposure are preschool-age children and children with nutritional deficiencies. Other groups who may be susceptible to lead exposure are people with genetic diseases affecting heme-synthesis (blood formation) and those with diseases of the kidney and nervous system.

Benzene

On- and off-site military and civilian populations were exposed and are currently exposed by way of inhalation of benzene in ambient air. Benzene is a volatile organic chemical used in the production of plastics, detergents, and pesticides. It is also a component of gasoline, vehicle exhaust fumes, and tobacco smoke (66). Because of its many uses, benzene is widespread in the environment. Benzene levels measured in the United States in ambient air have ranged from less than 1 ppb in rural areas to more than 100 ppb in urban areas (66). The following daily median benzene air concentrations were reported by the Volatile Organic Compound National Ambient Database (1975-1985): remote (0.16 ppb), rural (0.47 ppb), suburban (1.8 ppb), and urban (1.8 ppb). The air data represent 300 cities from 42 states.

The maximum concentrations of benzene found in ambient air in 1987 at stations 2 and 5 at McAFB were 1.63 ppbv and 2.00 ppbv, respectively. Concentrations of benzene detected in 1992 in four off-site residential yards near McAFB ranged from 0.40 ppbv to 0.54 ppbv. These maximum concentrations are similar to median concentrations reported in the national database above.

The Department of Health and Human Services has determined that benzene is a known human carcinogen. The CREG is 0.04 ppb. Exposures to the concentrations detected in 1987 and 1992 may increase the risk of developing cancer. However, inhalation exposures to the concentrations detected at station 2, station 5, and the residential yards are not expected to result in increased adverse noncancerous health effects.

Chronic benzene exposure adversely affects the body's ability to make red and white blood cells. Those effects have been observed following occupational exposure to ambient air concentrations of 30,000 ppbv. Other health effects of benzene range from fatigue, headaches, anorexia, dizziness, and liver toxicity to aplastic anemia and acute myeloblastic leukemia (66). Exposure to benzene may also cause damage to the reproductive organs and impair fertility in women exposed to concentrations greater than 1000 ppb (66).

Reports in the literature indicate that persons particularly sensitive to benzene include workers employed in industries that use or make benzene, people living near certain chemical manufacturing sites, cigarette smokers, and people living near landfills where benzene has been deposited (66). Pregnant women and their fetuses and immunosuppressed and malnourished persons are at particularly high risk for adverse health effects (66). Whether those populations have different or enhanced responses depends on the ability of the liver and kidneys to detoxify and excrete benzene, or on the existing compromised function of target organs such as the bone marrow. For those reasons, it is expected that elderly people with declining organ function and young children with immature and developing organs will be more vulnerable to benzene and other toxic substances than healthy adults (66).

1,1-Dichloroethene (1,1-DCE)

Off-site residents and on-site military and civilian personnel were exposed and are currently exposed to 1,1-DCE in ambient air by way of inhalation. Off-site residents were also exposed to 1,1-DCE in groundwater (private wells) until they were provided with municipal water in 1986. Any current exposure to contaminated water would occur only if the residents have continued to use the contaminated wells.

1,1-DCE is a man-made chemical and is not found naturally in the environment. It is used to make certain plastics (such as packaging materials, flexible films like plastic food wraps) and flame retardant coatings for fiber and carpet backing (67).

EPA has classified 1,1-DCE as a Class C chemical -- a possible human carcinogen by the oral and inhalation routes (67). In 1987, the concentrations of 1,1-DCE reported in ambient air at stations 2 and 5 were 0.11 ppbv and 2.44 ppbv, respectively. There is an increased risk of developing cancer at the levels found at Station 5; therefore, the exposures are of public health concern. An MRL has not been derived for acute, intermediate, or chronic inhalation exposure.

Air monitoring data received by ATSDR in Fall 1992 indicate 1,1-DCE levels of 0.29 ppbv at Station 2 (near residents' homes) and 1.73 ppbv at the Groundwater Treatment Plant, another air station on base. Because of the levels found, adults at the GWTP have an increased risk of developing cancer, and their exposures are of public health concern.

Off-site residents also were exposed to 1,1-DCE in contaminated groundwater by way of inhalation, ingestion, and dermal absorption. Off-site residential wells had a maximum concentration of 189.0 µg/L in 1986. Exposure by ingestion to that concentration could increase the risk that adults and children could develop cancer. Assuming a 1 L ingestion rate, the estimated exposure dose for children is 0.02 mg/kg/day. This estimated exposure exceeds the chronic MRL (0.01 mg/kg/day). The MRL is a concentration that is not expected to result in adverse noncancer health effects from exposure. Off-site residences were connected to municipal water in 1986. Therefore, adverse noncancer health effects may occur as a result of these past exposures.

Sampling in 1991 detected 17 µg/L of 1,1-DCE in off-site residential wells. Although off-site residences were connected to municipal water systems in 1986, residents who have continued to use water from contaminated wells may be at an increased risk of developing cancer. The estimated ingestion exposure doses for adults and children are two to five times below the chronic oral MRL (0.009 mg/kg/day); therefore, adverse noncancer health effects are not expected in population who continue to use the wells.

There is limited information in the literature on the human health effects of 1,1-DCE (67). Most of the information is from case reports and studies in which the concentrations and lengths of exposure are not specified, and concurrent exposure to other toxic substances cannot be ruled out (67). Given those limitations, available information indicates that inhaled 1,1-DCE can induce nervous system toxicity, and that repeated, "low-level" 1,1-DCE exposure is associated with liver and kidney toxicity (67). Central nervous system depression and symptoms of inebriation have been seen in persons acutely exposed to levels several thousand times greater than those found on and off site at McAFB.

Although information about populations that may be especially sensitive to 1,1-DCE is from animal studies, it is believed that the following groups may be particularly susceptible to its toxic effects: infants and young children, pregnant women, consumers of alcohol, people with liver, kidney, thyroid, and cardiac disease, and people who are fasting (67). Increased susceptibility to 1,1-DCE toxicity is largely caused by the formation of toxic intermediates during its metabolism. The production and biotransformation of toxic intermediates of 1,1-DCE can be influenced by metabolic inhibitors and inducers, and by the availability of precursors of compounds involved in detoxification. The presence or absence of those agents in an individual with any of the previously mentioned medical conditions may result in increased vulnerability to 1,1-DCE toxicity (67).

1,1,1-Trichloroethane (1,1,1-TCA)

Off-site residents and on-site military and civilian personnel were exposed and are currently exposed to 1,1,1-TCA in ambient air by way of inhalation. 1,1,1-TCA is a synthetic compound that has many industrial and household uses. In industry, it is widely used to remove oil or grease from manufactured metal parts. In the home, it may be in products such as spot cleaners, glues, and aerosol sprays.

EPA has not classified 1,1,1-TCA's ability to cause cancer by the oral and inhalation routes (68). In Fall 1992, the concentrations of 1,1,1-TCA reported in ambient air at station 2 (near residents' homes) were 0.18 ppbv in May and 18.04 ppbv in October. Levels of 0.21 ppbv and 4.4 ppbv were detected at the Groundwater Treatment Plant air station during the same period. Exposure to those concentrations does not exceed the acute inhalation MRL (300 ppbv), at which adverse noncancer health effects can occur.

Air monitoring data also included some results of sampling of private residents' yards. The concentrations of 1,1,1-TCA reported in ambient air at four homes ranged from 0.31 ppbv to 2600 ppbv. One residential yard had a detected ambient air concentration (2600 ppbv) above the acute inhalation MRL of 300 ppbv. Spraying activities in the yard during sampling (see Table 17) may have resulted in these elevated concentrations. Acute health effects may result from exposures to concentrations above the acute MRL. No adverse health effects from the exposure was reported to ATSDR.

The human health effects of long-term exposure to air containing specific levels of 1,1,1-TCA are not known (68). Existing information on the levels of 1,1,1-TCA that may affect human health is from animal studies. Limited case reports are available from occupational settings on acute exposures to "high" concentrations (68). Such exposures have resulted in nausea, vomiting, diarrhea, respiratory depression, and cardiac arrhythmias. Central nervous system depression is proportional to the exposure concentration; as the exposure increases, the degree of depression can range from mild motor impairment, to euphoria, to anesthesia. Disturbances in equilibrium and coordination have been seen in people following acute exposure to "moderate" concentrations of 1,1,1-TCA.

Although information about populations that may be especially sensitive to 1,1,1-TCA is from animal studies, it is believed that the following groups may be particularly susceptible to its toxic effects: smokers, consumers of alcohol, and people with cardiac disease (arrhythmias). People who take the medication phenobarbital for epilepsy may also be more susceptible to the health effects of 1,1,1-TCA (68).

Polychlorinated Biphenyls (PCBs)

PCBs are a family of synthetic chemicals that contain 209 individual compounds (known as congeners). There are no known natural sources of PCBs in the environment (69). PCBs have been used widely as coolants and lubricants in transformers, capacitors, and other electrical equipment.

PCBs were detected in surface soils in area SA 12/OU B at a maximum concentration of 240,000 mg/kg. Locations with high PCB concentrations (>500 ppm) were identified as "hot spots." Workers in that area and anyone entering the area to inspect or take possession of salvage material could ingest, inhale, or have dermal contact with PCBs. The areas are covered with perforated steel planking. However, the planking does not prevent human contact with the contaminated dust/soil.

Exposure of a worker in the area by incidental ingestion of soil to a "hot spot of 500 ppm" one day per week would result in an estimated exposure dose of 0.0001 mg/kg/day. The exposure would exceed the chronic MRL of 0.000005 mg/kg/day. Therefore, adverse noncancerous health effects may occur from exposures at the DRMO. Exposure to 500 ppm one day per week would also result in an increased risk of developing cancer. "Hot spots" are areas that have atypical concentrations of contamination. However, the DRMO has levels as high as 240,000 ppm. Thus, the evaluation of the "hot spot of 500 ppm" is considered to be representative of the possible estimated exposure for workers at the DRMO. This area is of public health concern.

Exposures once per year to 240,000 ppm would result in estimated exposures that would exceed the MRL. Therefore, this site is considered to be of public health concern in the past for anyone (including infrequent visitors) who entered the site and could have had access to the most contaminated areas. Exposure once per year to a "hot spot" of 500 ppm would not be of public health concern. It is most likely that occasional visitors were exposed to these less contaminated areas. These areas have been capped and the entire area will be capped in 1994.

It should be noted that health effects associated with one exposure route also may be found following exposures by other routes (69). Although exposure to PCBs by dermal contact has not been evaluated by ATSDR, it is known that contact with PCB-contaminated soil can result in absorption of PCBs (69). Health effects such as chloracne, redness, and skin rashes in people dermally exposed to PCBs have been reported in the literature (69). Therefore, exposures of McAFB workers and visitors to PCBs by ingestion and dermal contact may result in greater risk of developing adverse health effects.

Information on human health effects associated with chronic oral exposure to PCBs is inadequate and inconclusive. Oral toxicity studies in animals have established that the liver and skin are primary target organs of PCBs (69). EPA has classified PCBs as Class B2 -- probable human carcinogens by the oral route (69). That classification was prompted by animal data; exposures have resulted in liver cancer, leukemia, lymphomas, and gastrointestinal tract tumors.

People with compromised liver function, such as people with defective glucuronide conjugation mechanisms (Gilbert's, Crigler, and Najjar syndromes); infectious hepatitis; and persons taking medications potentially toxic to the liver may be especially sensitive to the adverse health effects of PCBs (69). Because of physiologic differences in the detoxification and excretion of PCBs, fetuses exposed to PCBs through the placenta can be more sensitive than adults. Breast fed infants of PCB-exposed mothers can be exposed through breast milk. Children taking the antibiotic novobiocin also may be more sensitive to PCBs (69).

Toxicologic Evaluation Summary

There is evidence of on-site exposure to VOCs by way of ingestion of groundwater (past exposure) and inhalation of ambient air contaminated with VOCs. On-site exposures have occurred to PCB-contaminated soil at the DRMO by incidental ingestion. Exposures to mercury in ambient air have occurred in the past in Building 252 by way of inhalation. Evidence exists of off-site exposure to VOCs by ingestion of water (past exposure) and inhalation of ambient air. Off-site exposure to heavy metals has occurred by ingestion of water and by incidental ingestion of sediments in Magpie Creek.

ATSDR's evaluation of exposures to PCBs in soil by incidental ingestion and dermal contact at the Defense Reutilization and Maintenance Office lot, indicate that they are of public health concern for both cancerous and noncancerous adverse health effects.Evaluation of ambient air data from Station 2 and 5 indicate that inhalation exposures to TCE, benzene, and 1,1-DCE are of public health concern and may result in an increased risk of developing cancer. Ambient air exposures to mercury in building 252 are of public health concern.

Evaluation of ambient air data from residential properties and air stations adjacent to the properties identified benzene, TCE, and 1,1-DCE as contaminants of public health concern. ATSDR's evaluation of off-site exposures indicates there is an increased risk of developing cancer from past exposures to the following chemicals in contaminated well water: TCE, 1,2-DCA, 1,1-DCE, vinyl chloride, and arsenic. Those exposures were of public health concern. The concentrations of vinyl chloride and cadmium in private well water may also have resulted in an increased risk of adverse noncancer health effects. Past and current exposure of children to cadmium by incidental ingestion of and dermal contact with contaminated sediment at Magpie Creek also may result in an increased risk of developing adverse noncancer health effects.

Certain on- and off-site populations have been and currently may be exposed to multiple contaminants by way of several routes. Those exposures are difficult to evaluate because interactions between the chemicals may be additive, synergistic, or both.

B. Health Outcome Data Evaluation

ATSDR conducts a review of health outcome data when completed exposure pathways have been identified; when the toxicologic evaluation indicates the likelihood of health outcomes; and when the community near the site has health concerns. Health outcome data for McAFB are available at the state level; they include infant death and birth rates for Sacramento County and for the state of California. Those data have been requested and will be evaluated as soon as they are received.

Other health outcome data sources at the state level, such as the California Tumor Registry and the California Birth Defects Monitoring Program, contain information on Sacramento County for 1987 and 1986 (70,71). ATSDR has requested the cancer incidence data and will evaluate it as soon as it is received.

In October 1992, the Air Force provided ATSDR with a report by the California Department of Health Services (CDHS) evaluating cancer incidence for census tracts 63, 64, 65, 72.02, 72.04, and 73 around McAFB (72). This preliminary review by CDHS did not find an unusual (greater than expected) cancer incidence in the area for 1987-1990. ATSDR also received the 1991 report of the California Birth Defects Monitoring Program for Sacramento County. A review of the number of birth defects in the county for 1986 and 1987 indicated that the overall rate of birth defects was similar to rates in other parts of California. Specifically, the overall rates of several birth defects (trisomies, cardiac defects, neural tube defects, and oral clefts) are similar in Sacramento County and other parts of California.

In 1984, the California State Department of Health Services, Epidemiological Studies Section, conducted a preliminary study to determine the feasibility of conducting a full-scale epidemiologic study of the community near McAFB. The study concluded that it was not feasible to conduct an epidemiologic study because "the chemical contaminant concentrations were not high enough to cause any measurable medical symptoms, and the demographic characteristics of the exposed population were inadequate to provide the statistical power necessary to detect an increase in adverse health effects if they had occurred" (7).

The feasibility study considered information available at the time it was performed. ATSDR has reviewed subsequent sampling information indicating that heavy metal contaminants, in addition to the VOCs considered in the preliminary study, may be present. Additional data from air and sediment sampling have also been reviewed; they identify off-site community exposures to multiple VOCs and heavy metals by oral and inhalation routes. Demographic analysis of the community showed that it is stable, not migratory. The community's stability was confirmed at an ATSDR public availability meeting, at which citizens stated they had lived in the area for more than 20 years. This new information warrants a reevaluation of the community to determine if follow-up activities are needed.

During the investigation of mercury contamination in Building 252, the occupational medicine department at McAFB decided to examine and test employees who were involved in renovation activities, as well as employees who had worked in the building, to determine if they had been exposed to inorganic mercury. Thirty-four individuals believed to have been at greatest risk of mercury exposure during the building's renovation were chosen for evaluation. Each individual completed a questionnaire and underwent a physical exam that included a complete blood count, urinalysis, and analysis of blood urea nitrogen and creatinine levels and 24-hour urine mercury levels (8).

The majority of Building 252 employees were moved to Building 237 (end of 1989) before renovation and remodeling activities, with the exception of an unspecified number of employees who continued to work in rooms 130 and 160 (73). Mercury contamination in this building was believed to have occurred when the high vacuum systems were deactivated during the renovation of the second floor. Renovation was started on March 1, 1990, and continued until May 17, 1990 (73). Using this information, exposure duration would have been two and a half months for the six employees involved in the renovation project and for the employees who worked in rooms 130 and 160 (73). Urine mercury samples were collected within a week to a month after exposures were supposed to have ceased (May 29-June 14, 1990 (73). Urine mercury samples should have been collected soon after exposure ceased to adequately measure exposures. Because of the time interval between exposure and urine sample collection, there may have been sufficient time for the kidneys to have eliminated appreciable levels of mercury in the body. Therefore, urine mercury levels may not be indicative of exposures to mercury for the reported two and half month period.

Of the 34 employees evaluated for mercury exposure, urine mercury analyses were either not done or reports of the results were not available for five of the employees. Follow-up medical information for an additional six employees was not available. Urine mercury levels measured were within the accepted occupational normal range (0-20 µg/L), and most results were comparable to the general population (4 µg/L) (8,62). Three of the employees tested had urine mercury concentrations above those of the general population; one had a urine concentration of 5µg/L, and two had urine concentrations of 6 µg/L (8).

According to the literature, mercury occurs naturally in the environment, and everyone is exposed to very low levels of mercury in air, water, dental fillings and food (62). Sources of greater exposure to metallic mercury would be mercury-contaminated air in the workplace or in any location where mercury might have been spilled (62).

Questionnaires completed by employees were reviewed to identify symptom patterns. Employees were asked if they had experienced the following: recent pain with chewing within the last 60 days, bleeding gums, prolonged bouts of diarrhea, unexplained loss of appetite, unexplained weight loss, personality changes, changes in sleep pattern and the type of changes if present, muscle tremors, skin changes, recent respiratory difficulties, history of kidney disease, seasonal allergies, family history of Parkinsonism/kidney disease/hyperthyroidism. Nine individuals reported seasonal allergies, 6 reported changes in sleep pattern, 6 reported personality changes, 5 reported skin changes, 5 reported muscle tremors, and 4 reported bleeding gums. The significance of the frequency of reported symptoms is unknown without additional information in regards to the duration or severity of symptoms, the time of onset in relation to work exposures or other work history information. The above symptoms are non specific and could be related to many diseases including mercury toxicity. Further medical information is needed to adequately interpret the symptom findings. (8,62)

According to the literature, urine mercury concentrations of 7- 1,101 µg/L have been associated with abnormal memory tests, decreased tibial nerve velocity and increased median nerve latency in both motor and sensory nerves (62). Other studies have associated short-term memory loss, increased tremors, and impaired eye-hand coordination with urine mercury levels of between 0 and 1000 µg/L (62).

ATSDR has no evidence indicating that mercury exposure reached levels at which acute toxicity would be expected. Urine mercury concentrations detected ranged from none detected to 6 µg/L (8). Sixteen of the 29 employees had urine mercury levels of 2µg/L or greater, indicating low-dose exposure to mercury. It is not possible to determine if those urine mercury levels are associated with exposure to the mercury contamination in Building 252, but, it is possible that exposures equivalent to the general population occurred in this building. It is believed that some employees may have been exposed to chronic (more than one year) low doses of mercury. ATSDR will determine appropriate follow-up health activities in the Public Health Action Plan of this Public Health Assessment.

During the remedial investigation/feasibility study sampling of OU B, preliminary results from SA-12 near Building 700 showed levels of PCBs of public health concern. The McAFB Base Occupational Medicine Department decided to conduct exposure evaluations of employees who worked in or around the PCB-contaminated area. The exposure evaluation included a revised questionnaire and laboratory blood analysis, including a liver profile and blood PCB levels. Twenty-nine of the 50 employees who work in the Defense Reutilization and Maintenance Office agreed to the exposure evaluation (74). ATSDR obtained the results of the PCB blood analysis for all employees tested. ATSDR did not receive data on the completed questionnaires or physical exams. The range of PCB blood levels was from none detected to 10 nanograms per milliliter ng/ml (75). According to the medical literature, the mean blood PCB concentration in a nonoccupational exposed population is between 4 and 8 ng/ml; 95% of such individuals have concentrations less than 20 ng/ml (69). Blood tests are the easiest, safest, and, possibly, the best method for detecting recent exposures to large amounts of PCBs (69).

According to the medical literature, dermal/ocular signs such as chloracne, skin rashes, pigmentation disturbances of skin and nails, eyelid edema, and conjunctivitis may be considered reliable indicators of long-term exposures to even low levels of PCBs only when exposure to other contaminants can be ruled out (69).

The concentrations of PCBs in the blood of employees tested do not indicate that exposure greater than that expected for the general population has occurred. However, those determinations do not rule out the possibility that low-dose, long-term exposure has not occurred. Because the employees are at a greater risk of exposure than the general population, periodic medical evaluations should be continued until remediation in the area has been completed.

C. Community Health Concerns Evaluation

In the following paragraphs, ATSDR addresses each of the community concerns about health:

  1. There appear to be many cases of cancer on Barbara Street and other locations west of the base. Could the high incidence of cancer deaths in the residential area west of the base be related to the groundwater contamination or other contaminated media at McClellan?

Cancer is not one disease, but many different diseases; different types of cancer develop for different reasons. Cancer is the second leading cause of death in the United States, exceeded only by heart disease. According to the American Cancer Society, approximately one person out of every four will develop cancer in his or her lifetime. In general, cancers take between 20 and 40 years to develop.

ATSDR does not have sufficient information to determine if there is an increased rate of cancer in that area. However, information that would be useful to determine if an epidemiologic study can be done would be the following: the type or types of cancer; the number of cases; the period during which they occurred; the geographic area; age and sex of those affected; the populations affected and at risk; and the suspected cause (76).

State cancer registry data were not reviewed at the time this public health assessment was completed because the data were not available. Site specific cancer registry data have been requested; ATSDR will review them when they are received and determine what follow-up health activities are indicated.

  1. Is there a risk of contamination to my vegetable garden if Magpie Creek overflows? Is it safe to use water from Magpie Creek for irrigation?

Environmental sampling of on-site surface water and sediment has not detected chemical contamination at levels of public health concern. There are no environmental sampling data for surface water in the off-site residential area, including Magpie Creek, where past chemical spills into the creek were reported. Additional sampling is required to respond to that concern. ATSDR will review the data if and when they become available.

Off-site sediment sampling was performed in the channel of Magpie Creek and metals, including cadmium, were detected at levels of health concern. Flooding has occurred in the past but there has not been any sediment sampling on the banks of the creeks or in residential yards. Thus, it is unknown if sediment contamination exists in vegetable gardens or yards. However, during creek overflows, the contaminated sediment could wash into these areas. The metals from the contaminated sediment, especially cadmium, could be taken up by plants and enter the food chain. Consumption of these plants would be of concern. However, this potential pathway cannot be fully evaluated due to lack of biota sampling.

  1. In the past, citizens have seen barrels in Magpie Creek and have heard reports of vats of TCE being pumped into the creek. One child who used to play in the creek has a cancerous tumor; could it be related to the past waste disposal into the stream? Are the levels of contamination in Magpie Creek dangerous to the health of children playing in and around the creek? Will overflow from the creek onto private property contaminate the soil where children play?

ATSDR has received reports that, in the past, large fuel spills were released from McAFB into Magpie Creek. Citizens reported that at times they saw solids, vats, and drums floating down Magpie Creek; at other times, the creek was discolored (green) and smelled bad. Those past practices could have resulted in accumulation of contaminants in the sediment and surface soil of Magpie Creek that could be released again into the surface water. Because TCE is volatile, it would not be expected to persist or bioaccumulate. Preliminary sampling data of sediment from Magpie Creek have detected heavy metals, such as cadmium and lead above environmental comparison values in all samples collected. Preschool and school-age children exposed to cadmium contaminated sediment by way of ingestion more than three times a week may be at an increased risk of adverse health effects. Health comparison values for lead are currently being revised by EPA; therefore, exposures to it cannot be evaluated. Cadmium is classified as a carcinogen by the inhalation route. Lead has been classified as a carcinogen by both inhalation and ingestion routes (65). Exposures to cadmium in sediment by ingestion and dermal contact are not expected to increase the risk of cancer in children. The risk of developing cancer from exposure to lead cannot be determined at this time. Because exposures to cadmium more than three times a week may increase the risk of adverse health effects, access to the creek should be restricted. (For more detailed information on specific contaminants, please refer to the Toxicological Evaluation section of this public health assessment.) Because sampling data for soil and surface water from Magpie Creek downgradient of McAFB are lacking, ATSDR cannot at this time address health issues associated with exposures to contaminants in surface water and soils in Magpie Creek.

In this public health assessment, ATSDR has identified sampling data gaps and has made recommendations for further environmental sampling of surface water and surface soil. ATSDR will review the sampling data as soon as they become available and will make appropriate recommendations.

  1. Is there any danger to livestock that graze around creeks? Is groundwater from irrigation wells safe for livestock?

Sampling data for sediment from Magpie Creek show evidence of both cadmium and lead. Both of those heavy metals are taken up from contaminated soil by the root systems of plants and grasses (49,65). Plants and fruits may absorb heavy metals and bioaccumulate levels that may be toxic to livestock. However, sampling of soil around Magpie Creek is lacking; therefore, ATSDR cannot assess the risk to livestock that might graze around the creek. Residents west of McAFB were connected to municipal water supplies in 1986-1987, after many residential wells were found to be contaminated. However, the residents were allowed to continue to use the wells to water lawns and gardens.

The VOCs and heavy metals (chromium, lead, mercury, arsenic, and cadmium) detected in groundwater samples from residential water supply wells were not at levels that would be expected to cause acute effects in livestock. Because those wells have not been sampled for some time, and because livestock, especially horses, are sensitive to heavy metals, residents who use private wells to water their livestock should consider having those wells tested. Because well-use documentation and groundwater sampling data for existing irrigation wells are lacking, a survey of the use of existing residential wells is needed. Such a survey would identify the potable, irrigation, and livestock water use of residential water wells in the area. The survey was recommended by ATSDR in its 1991 McClellan Air Force Base Health Consultation (Appendix E). In this public health assessment, additional sampling data needs are discussed; ATSDR will review the data when they become available.

  1. Is there an increased incidence of brain cancer on base?

Primary central nervous system tumors are rare. However, because of their location, they account for about 9-10% of all cancer deaths (77). Such tumors develop in the brain and the spinal cord and its coverings. Gliomas are the most common tumors of the brain. Glioblastomas are the most common of all gliomas; more than half of all intracranial brain tumors are glioblastomas (78). The only chemical reported in the literature to be associated with gliomas is vinyl chloride (80). Many other cancer causes or relationships have been suggested; however, none have been accepted as credible (78,79).

During the public availability meeting held in July 1991, many employees, especially those who work in Building 237, were concerned that there might be a high incidence of cancer on base. The cancer of particular concern to the employees is glioblastoma multiforme, a type of brain cancer from which two employees were reported to be suffering. In order to determine whether there is an excess of brain or other types of cancer on base, the California Cancer Tumor Registry database should be analyzed. At the time this public health assessment was completed, site specific data from the registry had not been provided to ATSDR. Those data will be reviewed as soon as they are available.

Although vinyl chloride has been detected in on-site soil gas and in groundwater monitoring wells, adequate surface soil and ambient air sampling data are lacking. The presence of vinyl chloride in any of those media could increase the risk of brain cancer in the exposed population. Because of the employees' concerns and the fact that brain cancer is rare, ATSDR has notified the base occupational medicine department of the community's concerns. ATSDR will maintain contact with the occupational medicine department and follow up as necessary.

  1. Could chemical exposures of employees who used to work in Building 252 be causing an increased rate of gout?

Gout is a rare metabolic disease characterized by high levels of serum urate and recurrent attacks of acute arthritis (80,81). Chronic lead intoxication has been associated with gout (80,82). For more information on gout, see Appendix F.

During the ATSDR on-site public availability session, employees from a section of Building 237 who formerly worked in building 252 stated that several members of their group have gout. The workers have no family history of gout. In order to adequately address this question, the affected employees must first be identified and medical exams must be conducted to confirm their diagnoses. ATSDR contacted the base occupational medicine department about the employees' concerns.

In reviewing the limited environmental data for the base, ATSDR noted that lead was found only in subsurface soil samples. Because the concerned employees are not involved in remedial work or construction, it is highly unlikely that they would be exposed to lead-contaminated subsurface soil. Other sources of lead may be vehicle exhaust, cigarette smoke, and lead-containing gasoline, paint, and plumbing. Exposure to lead can occur in occupations such as smelting and refining, steel welding and cutting, and battery manufacturing, as well as in gasoline stations and radiator repair shops. Some workers reported soldering occurred in this building; however, the location and duration of soldering is not known and no environmental air lead levels have been identified from Building 252.

Mercury has been identified as an occupational contaminant in Building 252. Some of the employees with gout may have been exposed to mercury while working in Building 252, but current medical literature has not associated mercury exposure with gout.

As a result of the ATSDR investigation into employees' concerns, the base occupational medicine department is considering conducting a health survey of Building 237. The health survey would determine the number of employees with gout and other health problems and their association with occupational exposures. ATSDR will maintain contact with the occupational medicine department as the health survey progresses.

  1. Why are so many people who worked in Building 252 getting cancer?

Many employees who worked in Building 252 now work in Building 237. Most employees interviewed expressed concern that there might be a high rate of cancer in their fellow workers. ATSDR has brought the cancer concerns to the attention of the base occupational medicine department. As stated previously, one of four persons in the general population are expected to develop cancer. There are many different types of cancer that may develop in people for multiple reasons including lifestyle, diet, smoking and occupation. In many cases there may not be a readily identifiable reason or cause. Because of those cancer concerns, a review of the cancer registry data is needed. The cancer registry data should provide information for specific types of cancer, adjusted for age and sex, and that pertains to the community involved (site specific). Site specific cancer registry data will be reviewed as soon as the data are made available to ATSDR. The review will compare the McAFB population to a similar population to determine if McAFB has an elevated cancer rate.

  1. Why are so many on-base workers suffering from chemically induced hepatitis, and why hasn't anything been done to prevent it?

Chemically induced hepatitis is a term defined as inflammation of the liver as a result of exposure to a chemical (83). Concerns about this type of hepatitis were expressed by several employees who work in Building 251, the seal/reseal building, who have been diagnosed with the disorder. Hepatic cancer in an employee who worked in Building 251 also concerns the employees. The base occupational medicine department is monitoring liver function in employees in this building following reports of two cases of pancreatic cancer in employees who worked in Building 251. Mild abnormalities of liver function have been detected in some employees; they have been reassigned to other jobs to prevent further chemical exposure (84). The base occupational medicine department is aware of the concerns and will continue to monitor employees in the building. All potential chemical exposures should be identified so that measures can be implemented to prevent adverse health effects. ATSDR will maintain contact with base occupational health staff. ATSDR's Health Activities Recommendation Panel also will review the concerns and determine appropriate follow-up health activities.

 
  1. Could any of the chemicals used on base in Building 252 cause bone deterioration?

Exposures to toxic concentrations of lead or cadmium on site may increase the risk of developing osteomalacia. Bone deterioration is defined as a loss or decline of bone mass (83). This question, however, does not specify the type of deterioration or degeneration of concern. Following are descriptions of two types of bone deterioration. Osteomalacia is a disease characterized by a gradual softening of the bones and more or less severe pain as a result of the lack of calcification (82). Osteoporosis is a condition in which there is reduction in the quantity of bone or atrophy of skeletal tissue (82,83,85). The clinical features of the two conditions are very different. Osteomalacia has been associated with excessive drinking of alcohol, long-term anticonvulsant drug use, ingestion of outdated tetracycline (antibiotic), and excess ingestion of heavy metals (e.g., aluminum, lead, and cadmium) and the element fluoride (82). Osteoporosis is usually caused by immobility, intestinal malabsorption, lack of estrogen, low calcium intake, and deficiency of vitamin D. Less common causes are nutritional or developmental disturbances, endocrine diseases, and bone marrow disorders. Other causes of osteoporosis are prolonged heparin use and tobacco smoking (82).

  1. What health effects, both short and long term, are associated with on- and off-site contaminants?

Short- and long-term health effects that may result from exposure to contaminants found on and off site have been discussed individually in the Toxicological Evaluation section of this public health assessment. In that section, ATSDR addresses specific contaminants of concern; the populations exposed; duration of exposure; route of exposure; the estimated exposure dose; and health effects that may result from chronic (longer than one year) exposure.

  1. What is the significance of finding vinyl chloride in the crawl spaces of homes west of the base?

Vinyl chloride is a volatile organic compound (VOC) found in plastic and vinyl products such as pipes, wire, and cable coatings. It is also a degradation product of other VOCs, such as TCE, PCE, and 1,1,1-TCA (55).

Vinyl chloride was not detected in ambient air samples taken from crawl spaces. The detection limits used were one to two orders of magnitude higher then the Cancer Risk Evaluation Guide; therefore, vinyl chloride may have been present in concentrations of potential public health concern, but was not detected. Although vinyl chloride was not detected in the crawl spaces of residences near OU D, other VOCs were found. The presence of VOCs in crawl spaces indicates that contaminated soil gas may be migrating. Exposures to VOCs in crawl spaces would be limited to maintenance workers who go underneath the affected homes or children who play in those spaces. It is also possible that VOCs in the crawl space ambient air could filter into residences, resulting in occupants being exposed by way of inhalation. Additional air monitoring in homes is needed to fully evaluate the health effects associated with this exposure pathway.

  1. Do any of the contaminants of concern cause Graves' disease?

The chemical contaminants of concern have not been associated with Graves' disease, which is a toxic goiter characterized by diffuse hyperplasia of the thyroid gland (a form of hyperthyroidism); the only substance known to cause the disease is iodine. Iodine is not one of the contaminants of concern at McAFB. Exposure to excess iodine can cause Graves' disease by directly stimulating the thyroid gland (86,87). For more information on Graves' disease, see Appendix F.

  1. Can any of the contaminants be linked to major depression at McAFB?

Major depression is a clinical syndrome characterized by a persistent disturbance in mood; depression is clearly distinguishable from previous functioning. The cause of major depression is not known (88). The diagnosis is made only after all other possible causes have been excluded. Depression can be secondary to illnesses, other mental disorders, alcohol dependency, and anti-hypertensive medications; those types are not considered major depression (82,88,89). For more information on major depression, see Appendix F. The chemical contaminants of concern at McAFB have not been associated with major depression.

  1. What are the effects on our health of combined exposures to the chemicals? Is there an increased risk of damage to the body following exposure to a combination of any two or more of the chemicals?

ATSDR has not evaluated the health effects of exposure to combinations of chemicals because very few research data are available. When simultaneous exposure to multiple chemicals occurs, additive, synergistic, or antagonistic interaction among the compounds is possible. The interaction of multiple chemicals may result in an increased risk of developing cancer and other adverse health effects.

  1. Asbestos was recently removed from hangars 360 and 362A. Are there health risks to workers who might have been exposed to the dust during removal?

ATSDR contacted base bioenvironmental engineering personnel to inquire about the removal of asbestos from hangars 360 and 362A. The agency was told that asbestos removal began in hangar 360. The asbestos removed from the hangar roof was nonfriable (did not crumble easily); it was removed from the exterior. Procedures were explained to hangar employees before the removal. Proper equipment and techniques for removal of the hazardous material were used. Because many workers in hangar 360 complained of dust in the building, air monitoring equipment was installed. No asbestos levels above acceptable limits were reported. More recently, asbestos was removed from the roof of hangar 362A. That asbestos was also nonfriable and was removed in the same way. Although air monitoring equipment was installed, employee concerns resulted in relocation of normal work operations until removal was completed. Air monitoring data indicated that asbestos levels during the removal were not of health concern (90). Because the asbestos was removed from the hangars using adequate safety guidelines, and because there were no detectable fibers in the samples taken, ATSDR does not believe that health effects are likely.

  1. Is groundwater being tested enough to ensure that residents still using residential wells are protected?

The current tracking and monitoring of the contaminated groundwater plumes emanating from McAFB appears adequate. Residences in the affected area now use municipal water for drinking water. Groundwater contaminant data on private wells are not current because sampling of those wells ended when the residences were connected to public water systems. Anyone in the contaminated groundwater plumes area who is currently using a private well for drinking water could be exposed. People using the groundwater for irrigation could be exposed by inhaling volatile compounds from the droplets of water spray in the air and by ingesting biota (produce) that have bioaccumulated contaminants. Therefore, a well use survey and a carefully planned and executed sampling and analytic protocol is necessary to identify the possibility of more exposures.

  1. Were contract employees exposed to PCBs in Building 624D during the months of January and February of 1985? Could those exposures have resulted in illnesses? If so, will health studies be conducted?

This concern was expressed by a former contract employee who worked in Building 624D in January and February of 1985. This employee stated that OSHA conducted wipe samples of several areas of this office space and detected PCBs at a level of 1.7 µg/100 cm2 in an area above the women's restroom (91). That concentration was within permissible limits, and the Air Force was not issued a citation. As a result of this concern, ATSDR requested and obtained breathing zone sampling data for Building 624D before and during the occupation by former contract employees (94). Fourteen samples taken on January 9, 1985, also showed PCBs at levels less than the detection limit of 0.005 mg/m3 (92). The OSHA PEL for the 1242 PCB congener is 1.0 mg/m3; the PEL for the 1254 congener is 0.5 mg/m3. The NIOSH REL for PCBs 1242 and 1254 is 0.001 mg/m3 for a 10-hour workday and a 40-hour work week over a working lifetime (93). Detected concentrations are less than 5-fold higher than the NIOSH REL. Also, exposures occurred for only two months. OSHA and NIOSH PELs and RELs are standards designed to protect workers from exposure to a specific chemical over a working lifetime. Because PCB exposures were short term and below the OSHA PEL, cancer and adverse noncancer health effects are not likely to result. From the available data, health study follow-up activities will not be required.

The following community health concerns were collected during the public comment period of this document.

  1. What are the immediate and long term health effects of mercury?

Because mercury occurs naturally in the environment, everyone is exposed to very low levels of mercury, in air, water, and food. On-site civilian personnel in Building 252 have been exposed to inorganic mercury in ambient air by way of inhalation. Skin and mucous membrane contact may also have occurred secondary to accidental handling and/or exposure to mercury vapor.

Eye irritation and a red, itchy rash may occur with relatively mild exposures to mercury vapor. Short-term exposure to high levels of inhaled mercury vapors may produce cough, difficulty breathing, chest pain, nausea, vomiting, diarrhea, fever and a metallic taste in the mouth. Irritation of the mouth and intestines and effects on the kidney (nephrotic syndrome) may also occur. Later, lung problems such as interstitial pneumonitis, necrotizing bronchiolitis, and pulmonary edema may develop secondary to inhalation of very high levels of mercury vapor. Contact with liquid mercury has been associated with a red, bumpy rash. Incidental ingestion of liquid elemental mercury is not absorbed well and therefore not likely to cause health effects (94).

Long-term exposure to high doses of metallic mercury by inhalation can cause psychological changes, insomnia, loss of appetite with weight loss, excessive shyness, and emotional instability, nervousness, irritability, headaches, and short-term memory loss. Other symptoms include tremor, numbness and tingling, and weakness of the extremities (94). Chronic mercury exposure can also damage the kidneys (62). Workers exposed to "high" concentrations for 60-80 hours a week, 7 days a week have developed incapacitating pain of the lower back and extremities, muscle cramps, and twitching. There is no information to show that mercury causes cancer in humans or animals. Full recovery is more likely after short-term exposures than long-term exposures, once the body clears itself of the contamination (62). The specific types of health effects that employees assigned to Building 252 could have experienced cannot be predicted because the duration and concentration of their exposures are not known.

  1. What are the health effects associated with exposure to BTEX and other solvents?

Solvents are a group of chemicals that are commonly used in industry and the home as cleaning agents, paint thinners, dry cleaning liquids, pesticides, detergents, alcohols and others. They are classified according to their molecular structure (aqueous, organic, aliphatic, cyclic, aromatic, etc.). The health effects of different solvents are complex and variable, however, certain generalizations can be made about each class of solvents.

BTEX refers to a group of solvents which include: benzene, toluene, xylene, and ethyl benzene. All of these compounds are solvents known as aromatic hydrocarbons which, in general, are local irritants and have effects on the central nervous system such as lightheadedness, drowsiness, and headaches (95). Benzene is associated with leukemia and is therefore considered a carcinogen and exposure should be minimized.

  1. What are the immediate and long term health effects of TERCO?

TERCO, as prepared today, is a mixture of four compounds: methyl ethyl ketone, ethyl acetate, toluene and isopropyl alcohol. It has been reported that past formulations included up to seven compounds, but information on those components was unavailable. The health effects of each compound in the current mixture will be discussed individually. No studies could be identified evaluating the health effects of the combination of compounds found in TERCO.

Methyl ethyl ketone (MEK) is a solvent used in a variety of settings. It can be found in many mixtures of paint thinner, lacquers, cleaners and adhesives. MEK is an irritant to the eyes, mucous membranes and skin. At high concentrations MEK can cause lightheadedness, dizziness and drowsiness. Skin contact can cause rash. Long-term exposure to MEK has been associated with peripheral neuropathy. MEK alone is not considered to be toxic to the nervous system but when used in combination with certain compounds it may increase the likelihood of peripheral neuropathy (96).

Ethyl acetate is a solvent commonly used in lacquers. It can cause respiratory tract irritation and drying of the skin. At high concentration ethyl acetate can cause dizziness, lightheadedness and drowsiness. No evidence of association with cancer could be found (96).

Toluene is a common solvent used in making paints, lacquers, adhesives, rubber, paint thinners, and in some printing and leather tanning processes. A central nervous system depressant, toluene may cause symptoms of headache, confusion, drowsiness and memory loss. Skin irritation may result from prolonged direct contact with toluene. No long-term health effects to toluene exposure are expected, however, brain, kidney and liver injury has been associated with long-term exposure to high concentrations of toluene among glue sniffers (96).

Isopropyl alcohol is commonly used in industry as a solvent and disinfectant and can be found in many household products including rubbing alcohol, antifreeze, cleaners, paint thinners, and personal hygiene products. Exposure to isopropyl alcohol can cause central nervous system depression including dizziness, poor coordination, and headache. If taken orally, isopropyl alcohol can cause stomach irritation, and heart and kidney effects. No evidence of association with cancer could be identified (96).

  1. Is bladder cancer associated with JP-4, Naptha, TCE or TERCO?

The bladder is a relatively common site of occupational cancer. Benzidine based dyes and alpha and beta naphthylamine are known compounds associated with bladder cancer (97). Risk factors identified in bladder cancer include: cigarette smoking, obesity, long term analgesic use, and meat ingestion. JP-4, naptha, TCE and TERCO have not been associated with bladder cancer.

JP-4 is a formulation of jet fuel containing various petroleum products such as naptha, gasoline, and kerosene (98-100). Exposure to JP-4 vapor can cause irritation of the respiratory tract headaches, nausea, and mental confusion. Direct contact can cause defatting, drying and irritation of the skin. Tumors have been observed in animals following skin exposure but no evidence of cancer in animal or human studies could be found. (98-100)

Naptha, another hydrocarbon solvent, is produced in two forms: petroleum distillate which contains aliphatic hydrocarbons and coal tar which contains mainly aromatic hydrocarbons. Petroleum naptha is a central nervous system depressant causing lightheadedness, headache, incoordination, and dizziness. Respiratory and mucous membrane irritation also occur. Coal tar naphtha also is a central nervous system depressant and irritant of respiratory and mucous membranes. In addition, renal and liver toxicity can result from coal tar naptha exposure. The presence of benzene in both coal tar and petroleum naptha can result in bone marrow depression and leukemia following exposure. No evidence of bladder cancer could be found associated with exposure to naptha. (98-100)

Trichlorethylene (TCE) primarily is a central nervous system depressant. Immediate health effects may include dizziness, headache, blurred vision, incoordination, flushed skin, tremors nausea, vomiting, liver dysfunction and irritation of the skin and mucous membranes. Long-term health effects from overexposure to TCE include hearing defects. It is classified as a probable human carcinogen, however no bladder cancer has been reported to be associated with TCE (50).

TERCO is a mixture of methyl ethyl ketone (MEK), toluene, ethyl acetate and isopropyl alcohol. Health effects of these compounds are described above. No studies could be found that associate bladder cancer with TERCO.

  1. What are the immediate and long term health effects of hydraulic fluid exposure: is hydraulic fluid associated with arthritis?

Major components of hydraulic fluid usually include ethylene glycol, propylene glycol and tri-ortho cresyl phosphate (TOCP). The composition of hydraulic fluid varies greatly and usually depends upon the specific conditions of use.

Limited animal studies suggest low toxicity by oral and dermal routes in rats and rabbits. In general, hydraulic fluids do not appear to be eye and skin irritants although specific formulations have produced sensitization. (98)

Limited information has been reported concerning human exposure to hydraulic fluids. Dermatitis has been reported and one case of polyneuropathy was reported in a mechanic who was heavily exposed to hydraulic fluids (98).

No studies could be found that associate arthritis with hydraulic fluid exposure.

  1. Are naptha, polysulfide primer or TERCO associated with headaches, panic attacks, or depression?

In general, these compounds all contain solvents that can cause central nervous system depression. Symptoms of exposure to these compounds can include headaches, confusion, lightheadedness, dizziness and incoordination. Under certain conditions (such as working on a ladder) these symptoms could contribute to an individual's falling. These compounds for the most part are not associated with long term effects on the central nervous system or psychological conditions such as depression.

Some chemicals may cause anxiety upon exposure due to their noxious odor. Anxiety, panic attacks, and depression may be reactions to stress. If an individual perceives chemicals in their environment and/or workplace as unsafe, exposure to these chemicals may contribute to an individual's stress level and increase symptoms of anxiety, panic attacks, and depression.

  1. Can contaminated well water or air contribute to allergies, colds, or bronchitis?

In general allergies, colds and bronchitis can be aggravated by many environmental contaminants. Dust, vapors, aerosols, and gases can be inhaled and irritate mucous membranes of the entire respiratory tree. Water contaminants can become airborne (aerosolized, vapors) at the tap (during showers) and inhaled and potentially cause irritation of the respiratory tract.

Many respiratory irritants may also be sensitizers. This means that after initial exposure to a compound repeated exposure to even very small concentrations can irritate the respiratory tree and produce an allergic response.

It becomes very difficult to identify which contaminants may be contributing to symptoms as either respiratory irritants or as sensitizers. Some individuals exposed to known sensitizers may never become sensitized or irritated by a compound. Others may be very sensitive to a variety of compounds. In general, minimizing exposure to respiratory irritants and allergens will reduce the risk of respiratory irritation and allergy. Allergy testing may help identify which air contaminants may contribute to an individual's specific health complaints.

  1. Could learning disabilities/attention deficit disorder be associated with environmental contamination?

Little is known about the causes of learning and behavioral disabilities such as attention deficit disorder. Epidemiological studies have looked at factors such as lower socioeconomic status, suboptimal labor and delivery outcomes, lower prenatal and perinatal care, and maternal drug abuse as possible causes of learning disabilities. No studies could be found that associate environmental contaminants with learning disabilities except for lead. Lead-induced effects on the nervous system have been associated with impaired learning and decreased long-term learning potential.

  1. Are heart attacks associated with nickel plating work or other chemical exposures?

Two chemicals in the work place are known to stress the cardiovascular system: methylene chloride and carbon monoxide. Methylene chloride affects the cardiovascular system because it is converted to carbon monoxide in the body . Carbon monoxide combines with hemoglobin in the body to produce carboxyhemoglobin. Carboxyhemoglobin displaces oxygen from the red blood cell resulting in hypoxia (lack of oxygen to tissues). Individuals with heart conditions may not be able to tolerate the stress of elevated carboxyhemoglobin levels. Methylene chloride and carbon monoxide overexposure may lead to angina and heart attacks in compromised individuals. (101)

  1. Could asthma, chronic lung disease and nasal polyps be associated with stripping paint of aircraft?

Paint stripping creates a variety of exposures including: solvents, paints, paint strippers, and dust produced by the process. Polyurethane paints, generally used on aircraft, also contain isocyanates. Some paints may also contain lead.

Isocyanates, many solvents and environmental dust all may contribute to respiratory irritation and contribute to symptoms of asthma and chronic lung disease. The specific type of paint and air contaminants used and the duration and concentration of exposure would be needed to help determine if exposure to a specific compound may have contributed to an individual's health complaints.

  1. Was the equipment that was moved from building 252 to building 237 decontaminated prior to moving?

McAFB staff have stated that no contaminated equipment was moved from building 252 to 237.

  1. Are private wells near 26th and I Streets contaminated?

In the past, water for some of the private wells in that area were contaminated with VOCs, such as TCE, and metals. The plume of groundwater contamination, which was flowing northwest off the base, had affected those wells. However, for several years a groundwater treatment plant at McAFB has been extracting (pumping out of the ground) the contaminated groundwater and treating it. That extraction process has resulted in pulling the plume back toward the base. Results of testing of a few private wells for the ATSDR health consultation (Appendix E) showed that the levels of contaminants in the well water was lower than levels seen in the early 1980s, but some contaminants were still present in the water. For that reason, ATSDR has recommended a private well use survey for homes in the residential areas west and south of the base; that survey would provide information on how the wells are used today and testing for the contaminants.

  1. Could a municipal well or private well near Magpie Creek be contaminated; would past dumping of heavy metals into the creek affect crops, fruit trees and well water?

A potential exists for wells in that area to be contaminated; for that reason, McAFB has an extensive monitoring well system off the base to identify areas of groundwater contamination. Owners of city wells are notified if the groundwater near the well is becoming contaminated. However, private wells are not tested on regular schedule since property owners were provided city water in the mid-1980s.

It is possible that past dumping practices could have released contaminants that would still exist in the Magpie Creek area, such as heavy metals. Volatile compounds, such as solvents, would have, most likely, evaporated from the soils. Recent sampling of sediments along the creek supported that idea; VOCs were not detected, but metals, such as chromium, cadmium, and lead were found in most of the samples. The levels of chromium were not of health concern, but cadmium, a metal that is known to accumulate in plants, is of concern. The sediment sampling occurred within the creek, not in areas of residential gardens. No biota sampling has been completed yet to confirm that chemicals, such as cadmium have accumulated in crops.

  1. Are city water systems, such as Rio Linda water, tested for the contaminants?

All the municipal water systems are tested on a required schedule for contaminants according to the Safe Drinking Water Act. Since McAFB uses water from the Northridge water system, the base also tests that water monthly for organic and bacteriological compounds monthly.

  1. Was a study made of workers on base related to the drinking water and chemical exposures in the workplace; will there be investigations of possible cancer clusters on and off base?

ATSDR's Division of Health Studies (DHS) is currently preparing to do a health study for residents west of the base; the DHS study may include a cancer cluster investigation. For more information on what is scheduled by DHS we would suggest that residents attend the DHS community assistance panel (or CAP) meetings ongoing with that community.

ATSDR recommended to NIOSH (the National Institute for Occupational Safety and Health) to investigate the need for health studies among workers at McAFB. NIOSH staff visited McAFB in the summer of 1993, met with workers on-site, collected information on exposures to chemicals in the workplace, and have issued a report (102). That report was sent to union representatives at the base and should be readily available.

  1. Base well 17 reportedly remained in use, even though contaminated, until 1985; why was that well not discussed in the section on base drinking water in the PHA?

The PHA discussed BWs 1, 2, 12, and 18 that were closed when TCE contamination was discovered in the groundwater (1979-1981). All wells being used then, and since that time, have been tested by the base for contaminants. As explained in the environmental contaminants section, choice of which base wells to close depended upon the levels of TCE at the distribution points around the base. Water from the wells were being blended, and some wells produced greater volumes of water than others. Therefore, a well could be contaminated and still not be removed from the system until the contaminant contribution from that well resulted in TCE levels at the distribution point at concentrations of health concern. The base has used several wells that were not discussed in the PHA for the above reasons.

  1. Is ATSDR going to assist people who have health problems associated with toxic substances at McAFB?

The actions that are underway and planned for the future by ATSDR and the Air Force are outlined in the Public Health Actions section of the public health assessment. The epidemiologic study planned by the ATSDR's Division of Health Studies may identify additional studies or actions needed to mitigate or prevent potential adverse health effects.

  1. What are the health risks of eating contaminated frog legs and crawfish from Magpie Creek?

ATSDR will need to know the identities and concentrations of contaminants present in frog legs, crawfish, or any other food chain entity to evaluate the health risks associated with eating the food chain entity. ATSDR has recommended that additional samples be collected from Magpie Creek to determine if contaminants that have the potential to bioaccumulate are present. If such contaminants are found, ATSDR has recommended that food chain entities in Magpie Creek be sampled.

  1. What are the health effects of air contamination, such as ash, off-base from the burning pits and fuel dumping by aircraft taking off and landing at McAFB?

Information regarding four separate burning pits was obtained from McAFB (12a). Materials burned or disposed of at the various sites included: refuse, ash, oily wastes, solvents, waste chemicals, waste fuels, and waste oils. Soils surrounding the burning pits contained buried burn debris, wood, plastic, metals, sludge, rubber and concrete. Specific compounds and their combustion by-products were not identified. The health effects of possible contaminants released into the air cannot be evaluated without more information on the identity of those compounds. If ash from those past practices still exists, it could be tested for any combustion products present that may be of health concern.

Jet Fuel (JP-4) is made by blending various proportions of distillate stocks, such as naphtha, gasoline, and kerosene (99). Inhalation exposure may occur from direct volatilization of aircraft fuel jettisoning (in-flight fuel release) and contamination of surface water and agricultural land, leading to ingestion with water or food (99).

Exposure to vapor can cause irritation of the respiratory tract, headaches, nausea, and mental confusion (99). Ingestion of JP-4 is irritating to the stomach. JP-4 and it's vapors (in high concentrations) may cause defatting, drying, and irritation of the skin when exposed (99).

  1. Could dioxins and furans form in overheated/burned transformers; how about smoking, space heaters, electrical filament heaters or gasoline/diesel powered fork lifts being operated in PCB-contaminated air?

Dioxins/furans are formed in trace quantities from combustion of products containing chlorobenzenes. The temperature required for dioxin formation is variously reported at values from 180 to 400 degrees Celsius. Products such as cigarette smoke, traffic emissions, fly ash from incinerators, heating system exhaust, and fireplace soot all contain trace amounts of dioxins/furans. Therefore, the processes questioned may themselves produce dioxins/furans as a result of the combustion process. The levels produced are expected to be trace amounts. (103)

PCBs in ambient air could be burned as a result of these processes in an area. However, the concentrations produced would be very small in relation to the level of contamination. It is expected that the PCB concentration in ambient air would have to be significant in order to produce dioxins/furans at levels of concern.

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