PUBLIC HEALTH ASSESSMENT
LOCKWOOD SOLVENT GROUNDWATER PLUME
(a/k/a LOCKWOOD SOLVENT GROUND WATER PLUME)
BILLINGS, YELLOWSTONE COUNTY, MONTANA
Some adults and children living in the Lockwood Solvents Site were exposed to VOCs fromseveral pathways. While a few of these residents drank contaminated water for about a yearsome time ago, most residents never drank water from their private wells. However, otherpathways existed at the site that could have lead to exposure to VOCs. These pathways includebreathing indoor air that contained VOCs from several sources. Those pathways are listedbelow:
- background VOC levels that are usually found in most American homes,
- VOC-contaminated water used for bathing that leads to VOCs evaporating to theair,
- volatilization of VOCs from other domestic use of private well water (forinstance, washing dishes, using toilets),
- volatilization of VOCs from groundwater into the gaseous spaces between soilparticles and the subsequent migration of VOCs in soil gas through a house'sfoundation into indoor air.
In addition, since VOCs can penetrate the skin and enter the body, some adults and children wereexposed to VOCs through their skin while bathing in VOC-contaminated water.
Since residents have expressed concern about exposure to VOCs from all of these pathways, thisevaluation will look at chemical exposure across pathways and will draw conclusions about itspublic health significance. Some uncertainty exists in evaluating chemical exposure acrosspathways because of the short-comings in science. These uncertainties will be described later inthis section.
Currently, adults and children are probably not exposed to VOCs in groundwater because thoseprivate wells with VOC levels above drinking water standards are no longer used for drinking orbathing. In addition, EPA has increased ventilation in the crawl space of a few houses that werefound to contain unusually high levels of VOCs in indoor air, thus, mitigating the impact fromthe soil-gas/indoor air pathway.
Appendix C contains a technical description of how exposure estimates were derived forinhalation exposure during and immediately after a shower, for dermal exposure during a shower,and for inhalation exposure during the remainder of the day. The combined exposure levels fromthese three pathways were used to determine the possibility of harmful effects from acuteexposures (exposures less than 14 days) and chronic exposures (exposures greater than 1 year).
The combined exposure levels were compared to inhalation guidelines to determine if furthertoxicological evaluation was required. If an inhalation guideline was exceeded, then thecombined exposure levels were compared to exposure levels from animal and human studies todetermine the possibility of harmful effects. As mentioned previously, Appendix C contains adetailed explanation of the approach for estimating exposure levels for the three differentpathways.
As mentioned previously, EPA and MDEQ detected VOC contamination in private wells in 1998and 1999. The maximum levels detected in private wells are shown in Appendix B, Table 6.
EPA and MDEQ also collected indoor air measurements from numerous homes in the LomondLane area from September 1999 through February 2002. The maximum levels detected in airfrom 1999 to 2002 are shown in Appendix B, Table 7 along with the average background levelsfor U.S. homes. Depending upon the chemical, the maximum level detected in the Lomond Lanearea occurred in either January or June 2000. A summary of the most recent air sampling data inFebruary 2002 is presented in Appendix B, Table 8.
Studies by the EPA have shown that most homes in the U.S. have measurable levels of organicchemicals in indoor air (Wallace 1987). While outdoor air contains these organic chemicals, asurprising finding from the EPA studies throughout the U.S. is that indoor levels of organicchemicals are usually higher than outdoor air. These higher indoor air levels of VOCspresumably come from consumer products that are brought into the homes, from off-gassing ofhome building materials, and from human activities. EPA studies showed that certain humanactivities were associated with having increased levels of chemicals in indoor air. Examples ofthese activities are listed below:
- smoking indoors increases benzene, xylene, ethylbenzene, and styrene levels in indoor air,
- bringing dry cleaning home causes higher PCE levels in indoor air,
- using hot water in the home increases chloroform levels in indoor air,
- parking a car in an attached garage leads to higher benzene levels in indoor air, and
- using room air fresheners, toilet bowl deodorizers, and moth crystals leads to higher levels of para-diclorobenzene in indoor air (Wallace 1987).
At least for some homes in the Lomond Lane area, VOCs are present in indoor air because ofthese multiple sources and activities. Some of the VOCs levels found in homes in the LomondLane area are similar to average background levels found in indoor air of other homes in the U.S. Tables 7 and 8 show that levels of 1,2-dichlorethane, chloroform, benzene, and carbontetrachloride are similar to or slightly above average background levels in other U.S. homes. Levels of PCE and TCE are significantly greater than average background levels found in U.S.homes. For some chemicals (e.g., dichloroethene, vinyl chloride, methylene chloride,bromodichloromethane) indoor air levels from other US homes are not available from EPAstudies. In conversations with Dr. Lance Wallace, the EPA researcher who studied indoor airlevels, he stated that the elevated levels of PCE and TCE were still within the range that onefinds in indoor air of U.S. homes. For instance, the 19 ppb of PCE is not uncommon forsomeone who brings dry cleaning home. However, for some of the homes in the Lomond Lanearea, it appears that the soil-gas pathway might be contributing to elevated levels of some VOCsbecause the homes with the highest levels of PCE and TCE in indoor air are also the homesclosest to the highest levels of groundwater contamination for PCE and TCE.
When estimating the possibility of harmful effects from elevated VOCs in private wells, ATSDRestimated the combined exposure from showering, from breathing indoor air during andimmediately after the shower, and from breathing background VOC exposure levels in indoor airduring the rest of the day and night. The combined exposure for each chemical was compared toavailable health guidelines and when appropriate to human and animal studies. It should benoted that exceeding a health guideline does not mean that harmful effects might occur. Rather,it means that a more detailed toxicological evaluation is needed. If a health guideline wasexceeded or if no health guideline exists, ATSDR compared the combined exposure level tohuman and animal studies to determine whether or not harmful effects might be possible.
Appendix B, Table 9 shows how the combined exposure level for each VOC compares toinhalation guidelines developed by ATSDR or EPA. ATSDR has three categories of inhalationguidelines based on the length of exposure: acute, intermediate, chronic. ATSDR developsinhalation guidelines for the following:
- acute exposures, which is defined as exposures up to 14 days
- intermediate exposures, which is defined as exposure from 15 days to 364 days, and
- chronic exposures, which is defined as exposures greater than 365 days (or 1 year).
EPA has developed a chronic, inhalation Reference Concentration, which is defined as exposuresup to 70 years. Whenever the combined estimated exposure for each VOC in Table 9 exceeds ahealth guideline, ATSDR evaluates the toxicity of that chemical further. This approachidentified four chemicals that require further evaluation. They are tetrachloroethene,trichloroethene, cis-1,2-dichloroethene, and vinyl chloride.
What follows is a comparison of the estimated combined exposures from inhalation and skincontact to health guidelines and when appropriate to human and animal studies. When exposuresare high enough, a discussion of the possibility of harmful effects is also given. The discussionis divided into acute exposures and intermediate/chronic exposures. Later in the section, ATSDRdiscusses the possibility of harmful effects based on concurrent exposure to multiple chemicals.
Tetrachloroethene: acute exposure
When showering, some adults and children will be exposed to high levels of PCE during andright after their shower. In addition to the inhalation exposure from breathing PCE thatvolatilized to the air, these residents also received exposure through dermal absorption. Toevaluate the toxicity of these exposures, it was necessary to combine the inhalation and dermalexposures to determine if harmful effects might be possible.
To combine the exposures, it is necessary to convert the quantity of VOC absorbed through theskin to an equivalent air concentration and to add that air concentration to the estimated airconcentration from volatilized PCE occurring from the shower. Table 10 in Appendix B showsthe estimated PCE concentration in air based on volatilization during a 10 minute shower, thedermal dose converted to an air concentration, and the combined dermal and inhalationexposures expressed as a concentration in air. These measurements are parts per billion or partsPCE per billion parts of air. It should be noted that unless otherwise specified in the text, ppbrefers to parts per billion in air and not to parts per billion in water.
From Table 10 in Appendix B, about 60% of someone's exposure comes from skin absorptionand about 40% comes from inhalation. Therefore, based on the assumptions used in estimatingdermal absorption, absorption through the skin is an important contributor to exposure.
As shown in Table 10, the combined PCE air concentration in the bathroom from dermalexposure and from volatilization is about 3,600 ppb for the adults who took showers using themost contaminated private well. The combined PCE air concentration in bathroom air fromdermal exposure and from volatilization is estimated to be about 2,500 ppb for children who usedthe most contaminated well. These estimated exposure levels exceed ATSDR's acute, inhalationMRL of 200 ppb, therefore, requiring further toxicological evaluation.
For adults, the estimated bathroom air concentration is about 14 times lower while for childrenthe estimated PCE level in bathroom air is about 20 times lower than levels that were shown tocause mild effects in human studies (Altmann 1992, ATSDR 1997a). In human studies, Altmannet al. exposed 16 men for 4 hours to 50,000 ppb PCE and showed the following effects:
- a decrease in repetitive response time to a repeated stimuli (a.k.a, vigilance),
- small changes in eye-hand coordination,
- a borderline increase in reaction time to a stimulus, and
- a decrease in nerve conduction involving the eyes (as measured by an increase in thevisual evoked potential latency.)
The authors did not find any changes in learning, memory, or mood in the tested subjects. Tosummarize the previous findings in more general terms, exposure to PCE at 50,000 ppb for 4hours each day for 4 days causes very mild changes in eye-hand coordination, changes in theability to respond as quickly to repeated stimuli, and changes in the eye's perception of stimuli.
For the Lockwood Solvents Site, the residents who used the most contaminated private wellsmight be at increased risk of the effects mentioned previously. Specifically, three private wellscontained PCE levels that might cause harmful effects in adults and children who used the wellsfor showering. However, one of the three private wells was not used for bathing; therefore only 2residences are a concern. Another three private wells had somewhat lower PCE levels thatresulted in some exposures for adults that were 60 to 330 times below levels that are known tocause harmful effects. For children, exposure levels were 90 to 480 times below levels that havebeen shown to cause harmful effects. To what degree adults and children who used these threeprivate wells might be at risk of harmful effects is uncertain. While the margin of safety (i.e.,ranging from 60 to 480 times) might be large enough, the concern is that PCE is not completelyeliminated from the body within 24 hours; therefore, by the time adults and children take anothershower the following day, some residual PCE remains in the body's fatty tissue thus increasingthe dose (i.e., amount of exposure) with time. Whether or not this increase in dose is enough tocause harmful effects is uncertain. ATSDR mentions it here as a possibility because of theeducational value it serves for residents who might be concerned about their health.
Some uncertainty also exists in deciding whether PCE might cause mild health effects in some adults and children because of the following reasons:
- the bathroom air concentrations are estimated,
- estimated exposure levels in adults and children were about 20 times lower than thelevels known to cause mild effects,
- part of the exposure level is based on estimating a bathroom concentration thatcorresponds to dermal absorption,
- the estimated duration of exposure for adults and children was less (one-half hour)compared to the duration of exposure that caused harmful effects (4 hours), and
- as mentioned previously, PCE dose might increase over time because of incompleteelimination from the body before the next exposure occurs.
Tetrachloroethene: chronic exposure
In addition to these peak exposure periods (i.e., acute exposure) to high levels of PCE whileshowering, some adults and children also were exposed to low levels of PCE for many years,which ATSDR refers to as chronic exposure. These chronic exposures resulted from acombination of peak exposure periods during showers followed by lower indoor exposuresthroughout the day. This combination of daily exposures could have been repeated for 15 to 25years for some residents. When evaluating these long-term (chronic) exposures, it is necessary touse an average PCE exposure level that represents PCE levels in the home throughout the day This average daily exposure is what is used to determine the possibility of harmful effects forchronic exposure over many years because it more accurately represents exposure.
At the Lockwood Solvents Site, ATSDR estimates that at the most contaminated private wellsome adults might be exposed to a daily average of 99 ppb PCE, and that some children might beexposed to a daily average of 78 ppb PCE (see Appendix B, Table 9). These levels exceedATSDR's chronic, inhalation MRL of 40 ppb.(2) Exceeding an MRL does not mean that harmfuleffects will occur but rather that further toxicological evaluation is necessary. As you remember,the highest indoor air level of PCE actually measured in Lockwood homes was 19 ppb (see Table7, Appendix B). Therefore, the estimated daily average level of 99 ppb reflects the additionalestimated exposure that occurs from taking a shower using water from wells with the highestPCE contamination.
Long-term human studies have shown that harmful effects have occurred in workers exposed to7,300 to 15,000 ppb PCE for many years. The effects observed include mild changes to thekidneys (10,000 ppb for 14 years), the loss of color vision (7,300 ppb for 2 years), and anincrease in reaction time (15,000 ppb for 10 years) (ATSDR 1997a).
Adults and children in Lockwood who used the highest contaminated wells might have beenexposed to estimated daily average PCE levels of 78 or 99 ppb. This estimated level is 74 to 94times lower than the levels that were associated with harmful effects in workers. There might bea small increase in the possibility of the harmful effects mentioned previously. Only one privatewell had PCE levels that might be a concern for chronic exposure over many years.
Tetrachloroethene: chronic exposure and cancer
PCE along with other solvents is a common commercial chemical used in the dry cleaningindustry. Because of their high PCE exposure, a number of epidemiological studies have beenconducted on dry cleaning workers. These studies suggest a possible association between long-term PCE exposure and an increased risk of cancer. The cancer types most consistently showingan increase are esophageal cancer, bladder cancer, cervical cancer, and non-Hodgkin'slymphoma. Unfortunately, dry cleaning workers are also exposed to other chemicals whileworking so it is difficult to determine whether PCE or some other chemical used in the drycleaning industry is the cause of these cancer. Another study of a community exposed to justPCE through their drinking water showed an increase in leukemia and bladder cancer in theexposed population (Aschengrau 1993, Webler 1993). Also adding to the complexity is thecontribution that smoking and other life-style variables might have on producing these cancers. One scientist has reviewed these studies and concluded that esophageal cancer might have beencaused by cigarette smoking and alcohol consumption and that bladder cancer might have beencaused by exposure to other solvents in the industry (Weiss 1995, ATSDR 1997).
PCE in air has been shown to cause cancer in rats and mice following near lifetime exposure. Ina 2-year study of rats, Mennear et al. showed an increase in mononuclear cell leukemia (a cancerof the blood) following exposure to 200,000 ppb PCE for 5 days a week, 6 hours a day. Mennearet al. also showed that PCE in air caused an increase in liver cancer in mice exposed to PCE at100,000 ppb for 5 days a week, 6 hours a day for over 2 years.
Much discussion exists in the scientific community about whether or not PCE exposure cancause cancer in humans. The Environmental Protection Agency is currently reviewing theircancer classification for PCE. The National Toxicology Program (NTP) within the federalDepartment of Health and Human Services has reviewed the available cancer information anddetermined that there is sufficient evidence that PCE can cause cancer in animals but theevidence in humans is inconclusive The NTP has concluded that PCE may reasonably beanticipated to be a human carcinogen (ATSDR 1997). NTP's summary of PCE carcinogenicitycan be found at this website: http://ehp.niehs.nih.gov/roc/ninth/rahc/tetrachloroethylene.pdf ).
One way to evaluate the possibility of PCE causing cancer in Lockwood residents is to comparethe estimated PCE levels in air to the levels in animal studies that have caused cancer. While thisapproach cannot provide a definitive answer that PCE might cause cancer in Lockwood residents,it gives some insight into the possibility of PCE causing cancer. Complicating this comparison,however, is the time frame of exposure. Some residents were exposed to relatively high levels ofPCE when showering while the animal studies exposed mice and rats for 6 hours a day, 5 days aweek.
The two exposure levels (Lockwood residents and animal studies) can be compared by using amargin of safety (MOS) approach. A MOS can be calculated by dividing the exposure level inanimals that caused cancer by the estimated exposure level in Lockwood residents from taking ashower in PCE-contaminated water. Table 11 shows the MOS using the estimated air level for a10 minute shower and a 20 minute bathroom stay. It also shows the MOS based on normalizingthe PCE level from 30 minutes to 6 hours so as to mimic the duration of exposure in the animalstudies.
Adults and children who used the most contaminated well had estimated PCE air levels of about3,600 ppb, which can be compared to the 100,000 ppb PCE air levels that caused leukemia inrats. The MOS approach shows that the estimated residents' exposure was 20 to 240 times lowerthan levels that caused leukemia in rats. Table 11 shows the calculated MOS for various PCElevels in water.
|PCE Level in Water ppb||Cancer MOS based on 30 minute bathroom air level||Cancer MOS based on 30 minute bathroom air level normalized to 6 hours|
* This is the MCL for PCE.
Another factor that complicates determining whether or not Lockwood residents have anincreased risk of cancer is that the variation in PCE levels in well water is not known. PCEmeasurements in 1998 and 1999 showed rather consistent levels for a residence. For instance, ifsomeone had elevated PCE levels in 1998, PCE levels were also elevated in 1999 and weresomewhat similar. However, it is not known if PCE levels were as elevated in the 1980s andearly 1990s. Lower PCE levels during those years would increase the margin of safety meaningthat cancer was less likely. Similar PCE levels during those years would mean that the margin ofsafety would be similar to those shown in Table 11.
In conclusion, while there might be an increased risk of cancer from PCE levels in some privatewells, it is difficult to make firm conclusions.
Trichloroethene: acute exposure
During and immediately after a shower, the estimated TCE level in the bathroom based onvolatilization and dermal exposure is 352 ppb for adults and 242 ppb for children (see AppendixB, Table 10). These TCE levels are below ATSDR's acute inhalation MRL of 2,000 ppb;therefore, harmful effects from TCE exposure while showering are unlikely (ATSDR 1997b).
To evaluate chronic exposure, it is necessary to average the TCE exposure over the course of theday. Combining the estimated inhalation and dermal exposures that occur while showering andthe inhalation exposure that occurs the remainder of the day gives an average exposurethroughout the day of 22 ppb TCE for adults and 16 ppb TCE for children who used the mostcontaminated private well (see Appendix B, Table 9). These TCE levels are below ATSDRintermediate MRL of 100 ppb; therefore, harmful effects are not likely for exposures up to 1year. Since most residents used their showers for longer periods, it is also necessary to evaluatethe potential for harmful effects from many years of exposure. However, too few studies exist toderive reliable health guidelines for inhalation exposure for these longer periods. The one studythat is available showed harmful effects to the kidney in rats exposed to 300,000 ppb TCE foralmost 2 years. The estimated combined exposure to TCE in adults and children who used themost contaminated wells is over 13,000 times lower than the level that caused kidney damage inrats. Based on the rat study, it seems unlikely that TCE will cause non-cancerous harmful effectsin Lockwood residents who used contaminated water for long periods (that is, many years). Some uncertainty exists in this conclusion, however, since only one study is available (ATSDR1997b, Maltoni 1988). A comprehensive review of the toxic effects of TCE can be found at thefollowing website: http://ehpnet1.niehs.nih.gov/docs/2000/suppl-2/toc.html (Scott 2000)
Trichloroethene: chronic exposure and cancer
In a recent review of human studies about TCE and cancer, Wartenberg et al. concluded thatevidence of excess cancer among workers is found for kidney cancer, liver cancer, and non-Hodgkin's lymphoma as well as cervical cancer, Hodgkin's disease, and multiple myeloma(Wartenberg et al. 2000). Wartenburg points out that occupational human studies usually involveexposure to other chemicals and other factors that might have caused the increase in cancer (forexample, smoking); therefore, it is not possible to positively conclude that TCE caused thecancers noted in these human studies.
The National Toxicology Program (NTP), a group of scientists within the Department of Healthand Human Services, has reviewed the scientific literature for TCE and concluded that TCE canbe reasonably anticipated to be human carcinogen. The NTP based this conclusion on limitedevidence of carcinogenicity from human studies and sufficient evidence from animal studies. The NTP also concludes that there is convincing relevant information that TCE acts throughmechanisms indicating it wold likely cause cancer in humans.
The NTP provides the following summary of human and animal studies:
"Epidemiological data are limited for evaluating the carcinogenicity of TCE in humans. Studies have suggested that occupational exposure to TCE causes cancer of the liver andbiliary tract, and also non-Hodgkin's lymphoma (IARC V63, 1995). Another study hasindicated that occupational exposure to TCE has been assoicated with cancer of thekindeys (Henschler et al., 1995a,b; Bruning et al., 1997). Results of three cohort studiesconsistently indicate an excess relative risk of cancer of the liver and biliary tract, with atotal of 23 observed cases, whereas 12.87 were expected (RR= 1.8), and a moderatelyelevated risk for non-Hodgkin's lymphoma (IARC, V63, 1995). Further, the suggestedmarginally increased risk for non-Hodgkin's lymphoma in areas with TCE-contaminatedgroundwater deserves mention (IARC V63, 1995). For a cohort of cardboard workersexposed almost exclusively to high levels of TCE, the standardized incidence ratio forkidney cancer was 7.97 (95% CI = 2.59018.59) (Henschler et al., 1995a).
The findings in humans are predated and supported by evidence in experimental animals. Target site concordance for TCE-induced tumors is consistent between humans androdents. In mice, TCE causes increases in benign and malignant tumors of the liver (NCI2, 1976; Maltoni et al, 1988); cited by IARC V63, 1995; NTP 243, 1990), increases intumors of the lung (Maltoni et al., 1988; cited by IARC V63, 1995), and lymphomas(Henschler et al., 1980). In rats, TCE induces cancers of the kidney (Maltoni et al., 1988;cited by IARC V63, 1995; NTP 243, 1990; NTP 273, 1988), interstitial cell tumors of thetestis (Maltoni et al., 1988; cited by IARC V63, 1995; NTP 273, 1988), and possiblyleukemias (Maltoni et al., 1988; cited by IARC V63, 1995)."
In addition to NTP, the International Agency for Research on Cancer (IARC) has also classifiedTCE as reasonably anticipated to be a carcinogen based on limited human studies and sufficientanimal studies. The EPA previously classified TCE as a probable human carcinogen but haswithdrawn its classification for further review. The EPA is reviewing its methods for estimatinga numerical cancer risk for TCE exposure; therefore, it is not possible to numerically estimate thepotential risk of cancer from showering in TCE-contaminated water. Several animals studiesexist where near-lifetime exposures to TCE caused cancers. The lowest level known to causecancer in rodents is TCE exposure in mice to 100,000 ppb for 18 months. This exposure causedan increase in lymphomas. In a 2-year study in rats, exposure to 100,000 ppb TCE caused anincrease in cancer of the testicles, while a 2-year study in mice exposed to 150,000 ppb TCEshowed an increased in lung cancer (specifically lung adenomas and adennocarcinomas). Incomparison, the highest estimated TCE exposure at the most contaminated private well is about22 ppb based on an average chronic (long-term over many years) exposure. This estimatedexposure is about 4,500 times lower than the lowest level that caused cancer in mice. Based on this comparison, it seems unlikely that TCE would cause a cancer in Lockwood residents.
Cis-1,2-dichloroethene: acute exposure
For the few residents who used the most contaminated water, the estimated acute combinedexposure from taking a shower is about 1,900 ppb cis-1,2-dichloroethene (DCE) for adults andabout 1,300 ppb for children. ATSDR does not have an acute MRL for cis-1,2-DCE because theinhalation studies conducted so far have only tested trans-1,2-DCE, a chemical with a similarstructure to cis-1,2-DCE. The estimated combined exposure level from taking a shower (i.e.,1,900 ppb and 1,300 ppb cis-1,2-DCE, see Appendix B, Table 10) exceeds ATSDR's acuteinhalation MRL of 200 ppb for trans-1,2-DCE. Exceeding an MRL does not mean that harmfuleffects are possible but rather that a more detailed toxicological evaluation is necessary.
No reliable human studies are available for cis- or trans-1,2-DCE; therefore, it is necessary toevaluate animal studies. The most sensitive animal study showed that rats exposed for 8 hours to200,000 ppb trans-1,2-DCE experienced mild (microscopic) changes in the lungs and liver(Freundt et al. 1977, ATSDR 1996). A similar experiment in rats was conducted with exposureoccurring 8 hours a day, 5 days a week, for 1 to 2 weeks, again to 200,000 ppb trans-1,2-DCE. This exposure also caused mild (microscopic) changes in the lungs and liver (Freundt et al. 1977,ATSDR 1996). The exposure levels in adults and children from Lockwood who used the mostcontaminated wells are about 100 times lower than the level that caused harmful effects in rats. In addition, the length of time adults and children were exposed was much less (one-half hour inadults and children compared to 8 hours of exposure in the animal study). For these reasons, itseems unlikely that harmful effects would occur in adults and children because of cis-1,2-DCEexposure.
Cis-1,2-DCE: chronic exposure
To evaluate chronic exposure to cis-1,2-DCE, it is necessary to average the cis-1,2-DCE levelsthroughout the day. The average exposure level to cis-1,2-DCE for residents who used the mostcontaminated wells is 42 ppb for adults and 35 ppb for children (see Appendix B, Table 9). Thisexposure level is below ATSDR's intermediate MRL of 200 ppb for trans-1,2-DCE; therefore,harmful effects are not likely for exposures up to 1 year. It is not possible to evaluate exposurethat occurs for many years because no human or animal studies are available.
Vinyl chloride: acute exposure
The estimated acute level of vinyl chloride in air based on combining inhalation and dermalexposure is 935 ppb for adults and 643 ppb for children (see Table 10, Appendix B). Theseestimated vinyl chloride levels exceed ATSDR's acute inhalation MRL of 500 ppb and thusrequires further evaluation. The most sensitive acute non-cancerous effect identified for vinylchloride occurs at an exposure level of 500,000 ppb in mice and rabbits (John et al. 1977, 1981,ATSDR 1997c). Pregnant mice and rabbits were exposed to 500,000 ppb for 10 days, 7 hours aday, during gestation days 6 through 15. The adverse effect observed was a delay in boneformation (i.e., ossification) in fetuses whose mothers were exposed to 500,000 ppb. This effectdid not occur in fetuses whose mothers were exposed at 50,000 ppb. The estimated exposure of935 ppb in some adults who used the most contaminated wells while showering is about 530times lower than the level that caused a delay in fetal bone formation. Because of this largemargin of safety and because residents' duration of exposure while showering is much less thanthe 7 hour duration of exposure in the animal study, harmful effects in people from taking ashower are not likely. About 20% (or 2 out of 10) of pregnant female mice died after beingexposed to 500,000 ppb vinyl chloride 7 hours a day for 10 days. Death was not reported inpregnant mice exposed to 50,000 ppb in the same experiment.
Vinyl chloride: chronic exposure
ATSDR does not have a chronic inhalation MRL for vinyl chloride but has developed an intermediate MRL of 30 ppb. For residents in Lockwood who used the most contaminated wells, the estimated chronic exposure level in air averaged over the day is 19 ppb for adults and 17 ppb for children (see Appendix B, Table 9). Since the estimated exposure levels are below the intermediate MRL, harmful effects are unlikely for exposures up to one year.
Some residents, however, were exposed for many years, so it is necessary to evaluate vinylchloride exposure for these longer periods. Only one study is available, and it is a rat study thatlasted one year. In this study the most sensitive effect identified was an increase in kidneyweight, a decrease in body weight, and damage to the testicles of rats exposed to 100,000 ppbvinyl chloride for 12 months, 6 days a week, 6 hours a day. These effects were not seen at10,000 ppb (Bi et al. 1985, ATSDR 1997c). The estimated exposure levels in Lockwood adultsand children who used the most contaminated wells are 5,200 times lower for adults and 5,900times lower for children when compared to the exposure level in rats that caused the previouslydescribed harmful effects. Because of the large margin of safety (5,200 and 5,900 times), itseems unlikely that harmful effects are possible in Lockwood adults and children. However,very few studies have been conducted for chronic exposure to vinyl chloride; therefore, thelimited number of studies adds uncertainty to the conclusion about harmful effects beingunlikely.
Vinyl chloride: chronic exposure and cancerous effects
In addition to non-cancerous effects, vinyl chloride has been shown to cause cancer in humansand rodents. Occupational studies have proven that vinyl chloride exposure over many years cancause liver cancer, specifically angiosarcoma of the liver. Angiosarcoma of the liver is very rare,with 25 to 30 cases occurring each year prior to vinyl chloride being used in industry. About 30years after the introduction of vinyl chloride, workers exposed to high levels of vinyl chloridewere found to have an increased rate of liver angiosarcoma. Additional human studies haveshown mixed results concerning other cancers. Some studies have shown an increase in cancerof the brain, central nervous system, lung and respiratory tract, leukemia, and lymphoma, whileother studies have not found an increase. These mixed results are not surprising considering thelimitations of conducting human studies. For vinyl chloride, the liver is the most sensitive organfor finding cancer (ATSDR, IRIS)
While the human occupational studies are sufficient to show that vinyl chloride causes liverangiosarcoma and possibly other cancers, the exposure levels to vinyl chloride (that is, the doseestimates) for these occupational studies are uncertain. Therefore, it is necessary to use the moreprecise doses that are achievable from rodent studies for comparisons and making decisionsabout the possibility of cancer in people. The most sensitive rodent study showed that ratsexposed to 5,000 ppb vinyl chloride for 52 weeks (5 days a week, 4 hours per day) experiencedmore mammary gland tumors than rats that were not exposed (Maltoni et al 1981, ATSDR1997c). Converted to a 24-hour exposure, the exposure level in rats is 600 ppb. The next mostsensitive rodent study involves mice exposed to 50,000 ppb for 52 weeks (5 days a week, 6 hoursper day), which is about 9,000 ppb averaged over 24 hours (Drew et al 1983, Lee et al 1977 and1978, ATSDR 1997c). This study showed an increase in cancer of the peritoneum, mammarygland, lymphoma, liver, and lung compared to mice that were not exposed. These exposurelevels of 600 ppb and 9,000 ppb can be compared to the estimated daily exposure in the fewadults and children who used the most contaminated water. Their estimated exposure levelaveraged over the day is about 19 ppb for adults and 17 ppb for children. These estimatedexposures for Lockwood residents who used the most contaminated private wells are about 30times lower than the level that caused cancer in rats and about 470 times lower than the levelthat caused cancer in rats.
Another approach for evaluating the possibility of cancer in residents involves a mathematicalestimate of the cancer risk. Using EPA's mathematical approach for estimating a theoreticalcancer risk based on the results of animal studies, a cancer risk of 1 extra case of cancer can beestimated for every 10,000 people exposed to the highest levels of vinyl chloride at theLockwood Solvents Site. What this means is that if 10,000 people were exposed to 19 ppb vinylchloride for 25 years, 1 extra case of cancer might be found. This theoretical estimate of cancerrisk assumes a linear relationship between cancer and exposure level so that even at low levels ofexposure cancer might be possible. This concept may or may not be true because it estimatescancer risk at exposure levels for which there are no data to confirm the actual risk. In addition,it assumes that for the people who had the highest contaminated well, they were exposed daily tothe highest level of vinyl chloride detected in their well. Because only a few water samples werecollected over a short period, it is not possible to determine an average vinyl chloride level,which would give a better estimate of cancer risk.
Based on these two approaches, residents who used the most contaminated private wells forshowering for many years may have an increased risk of cancer from exposure to vinyl chloride. It needs to be emphasized, though, that much uncertainty exists in knowing the vinyl chloridelevels that might have existed in years past. This uncertainty makes it difficult to draw firmconclusions about the possibility of cancer.
The remaining VOCs in private well water yield very low levels in indoor air from showering incontaminated water. They are listed as minor contaminants of concern in Table 9 along withchemicals that were detected in indoor air at very low levels. Both group of chemicals are atlevels in air that are below ATSDR's inhalation MRLs. For instance, the combined exposure tomethylene chloride from showering and from indoor air is estimated to result in an averageindoor air level throughout the day of 42 ppb. This estimated level is below ATSDR's chronicand intermediate MRLs of 300 ppb. Being below the MRL means that harmful effects are notlikely. Since the chemicals listed as minor contaminants of concern are below ATSDR's healthguidelines, they are not expected to cause harmful effects at the estimated levels of exposure.
Certain people are potentially more sensitive to the effects of VOCs. These more sensitivegroups include chronic consumers of alcohol; people with heart, liver, or kidney disease; peopletaking disulfiram (a medication used to treat alcoholism); and people taking the anticoagulantwarfarin. ATSDR's MRLs take into account the increased sensitivity of individuals sosomeone's exposure is below the MRL they are not risk of harmful effects even if they have oneof the conditions previously mentioned. If, however, they bathed in water with elevated PCE,then the conditions mentioned previously would put them at increased risk of experiencingharmful effects.
While EPA tested 33 private and commercial wells and one irrigation well in the LockwoodSolvents Site, only a few wells have VOC levels are a public health concern. Fourteen of the 34wells tested had VOC levels that were consistently above EPA's drinking water standards, thatis, the Maximum Contaminant Levels (MCL). Exceeding an MCL does not mean that harmfuleffects are possible but rather that the water does not meet drinking water standards for publicmunicipal water supplies and therefore is not acceptable as drinking water. The reason harmfuleffects are not automatically expected is that a safety factor is included in developing the MCL sothat the MCL is much lower than the level that is likely to cause harmful effects. Of the 14contaminated wells, 6 wells had VOC levels at or near the MCL, 5 wells had a moderate VOCcontamination, and 3 wells were highly contaminated.
To evaluate the possibility of harmful effects occurring in residents who used these wells, it is necessary to estimate the combined exposure to each VOC. In reviewing the data, the 14 contaminated wells could be classified into three groups: low, moderate, and high. The range of VOC levels in drinking water along with the number properties in each group are shown below:
|High ppb||Moderate ppb||Low ppb||At or below the MCLs|
|PCE||500 to 2000||80 to 450||6 to 79||0 to 5|
|TCE||100 to 150||40 to 90||6 to 39||0 to 5|
|cis-DCE||300 to 600||161 to 299||71 to 160||0 to 70|
|Vinyl Chloride||40 to 190||9 to 30||3 to 5||0 to 2|
The previous health discussion pointed out that acute and chronic exposure to TCE, cis-DCE, and vinyl chloride from taking showers using wells with the highest contamination (i.e., the high exposure group) were not likely to cause non-cancerous harmful effects in adults and children. Therefore, the same conclusion applies to adults and children who used wells with lower levels of TCE, cis-DCE, and vinyl chloride (i.e., wells with moderate and low contamination).
The only concern for possible non-cancerous harmful effects was acute and chronic exposure toPCE from taking a shower. Therefore, it is necessary to evaluate how much PCE exposure wasoccurring in adults and children who used wells with lower PCE levels in water. For wells at orbelow the MCL, adults and children are not likely to experience harmful effects from using wellwater for showers. For the low exposure group with PCE levels ranging from 5 to 79 ppb in wellwater, the estimated exposure to PCE is over 700 times lower than the levels that caused harmfuleffects in humans. Because of this large margin of safety, adults and children in the lowexposure group are not likely to experience non-cancerous harmful effects from PCE exposure.
For adults and children in the high exposure group with PCE levels in water from 500 to 2,000ppb, the level of PCE exposure ranges from 14 to 27 times lower than the levels that are knownto cause mild harmful effects in humans. These residents are at risk of experiencing some mildeffects.
For the moderate exposure group with PCE levels ranging from 80 to 449 ppb, the level of PCEexposure ranges from 60 to 300 times lower than levels that are known to cause harmful effectsin humans. It is uncertain to what degree these adults and children might be at risk of harmfuleffects. One concern here is that PCE is not completely eliminated from the body within 24hours; therefore, by the time adults and children take another shower the following day, someresidual PCE remains in the body's fatty tissue thus increasing the dose with time. Whether ornot this increase in dose is enough to cause harmful effects is uncertain; however, ATSDRmentions it here as a possibility because of the educational value it serves for residents whomight be concerned about their health.
Total Exposure to VOCs
To evaluate total exposure to VOCs, some assumptions are needed. In this case, the chlorinatedsolvents, the most significant contaminants at the Lockwood Solvents Site, will be addedtogether to evaluate total exposure. The assumptions made in order to evaluate total chlorinatedexposure follow:
- The chlorinated solvents (PCE, TCE, the DCEs, the dichlorethanes) act in a similarmanner to cause harmful effects. For example, they not only affect the same organ but doso by way of the same molecular mechanism.
- The combination of chlorinated solvents act in an additive manner, that is, the combinedeffect of chemicals is equal to the sum of the individual effects when each chemical isgiven alone. This is often put in equation form as 2 + 3 = 5.
- The combination of chlorinated solvents does not act in a synergistic manner. Synergisticeffects occur when the combined effects of the chemicals are greater than the sum of theindividual effect of each chemical when given alone. This is often put in equation formas 2 + 3 = 10.
At this time, insufficient information exists to determine if synergistic effects are occurringamong the chlorinated solvents. Since many chlorinated solvents affect the nervous system, it isreasonable to assume that chlorinated solvents might act in an additive manner to cause nervoussystem effects.
The assumption that chlorinated solvents act in a similar manner in producing adverse effects istenuous one and might not be correct. For instance, PCE and TCE cause changes in fatty acidcomposition in the brain. However, even though their metabolism in the body is somewhatsimilar, the degree of metabolism differs. PCE is poorly metabolized by the body and most of itis eliminated as PCE in a person's breath; whereas, TCE is well metabolized by the body and it iseliminated as metabolic by-products in the urine and as TCE in the breath. Compounding PCEand TCE, is cis-DCE. Cis-DCE is known to inhibit the liver's ability to metabolize chemicals. Since TCE is metabolized by the liver to produce its metabolic by-products, DCE might reducethe liver's ability to metabolize TCE thus causing more TCE molecules to be present in the body. Exactly how these chemicals might interact with the other chemicals is not known so this addsuncertainty to any conclusions that might be reached about the combined effect of exposure tothese chlorinated VOCs.
The other non-chlorinated chemicals in water and air will not be added to this total exposureevaluation for chlorinated solvents because their metabolism in the human body is likely to bedifferent from the chlorinated solvents.
The estimated indoor air levels of the chlorinated solvents are shown below. These estimates are based on combining inhalation exposure and dermal exposure.
|Chlorinated VOC||chronic exposure||acute exposure|
|PCE||99 ppb||3,587 ppb|
|TCE||22 ppb||352 ppb|
|Cis-1,2-dichloroethene||42 ppb||1,907 ppb|
|1,1-dichloroethene||0.2 ppb||10 ppb|
|1,1-dichloroethane||0.8 ppb||28 ppb|
|Total||164 ppb||5,884 ppb|
These chlorinated solvents total 164 ppb for chronic exposures and 5,884 ppb for acute exposures. First, let's evaluate chronic exposures. When evaluating the possibility of harmful effects from chronic exposures, totaling the chlorinated solvents results in an exposure dose that exceeds ATSDR's chronic MRL for PCE of 40 ppb (see Table 9). As mentioned previously for PCE, human studies have shown that harmful effects have occurred in workers exposed to 7,000 to 15,000 ppb PCE for many years. The effects observed include mild changes to the kidneys (10,000 ppb for 14 years), the loss of color vision (7,300 ppb for 2 years), and an increase in reaction time (15,000 ppb for 10 years) (ATSDR 1997a).
Adults and children in Lockwood who used the highest contaminated wells might have acombined exposure of 164 ppb total chlorinated VOCs. This combined total of 164 ppb is about45 to 90 times below levels that are known to cause harmful effects. While there might be asmall increase in the possibility of the harmful effects mentioned previously, they seem unlikelyin these residents with the highest exposures.
The estimated combined exposure to total chlorinated VOCs of 164 ppb also exceeds ATSDR's intermediate MRL for TCE of 100 ppb. Investigating this further shows that the MRL is basedon a 6-week study in rats who were exposed to 50,000 ppb TCE. The rats showed decreasedwakefulness during exposure and a decreased sleeping heart rate after exposure ended. Eventhough the intermediate MRL is exceeded, it seems unlikely that adults and children at theLockwood Solvents Site will experience these symptoms because of the following:
- the length of exposure in adults and children is significantly less (30 minutes in residents compared to 8 hours a day in rodents), and
- the amount of exposure is about 300 times lower in adults and children at LockwoodSolvents Site compared to the rat study that showed harmful effects.
For acute exposures, summing the individual chlorinated solvents yields an exposure level ofabout 5,884 ppb. When evaluating the acute toxicity of PCE, adding the chlorinated solventsincreases the exposure dose for PCE and reinforces the conclusions that acute exposure fromtaking a shower might cause mild damage to the nervous system. In addition, evaluating thecombined exposure for all chlorinated solvents might change the possibility of harmful effectsfrom TCE. TCE has been shown to make mice more susceptible to bacterial infection whenmice are exposed for 3 hours to 10,000 ppb TCE. The level of TCE alone in bathroom air(combined with dermal exposure) is 352 ppb. If PCE and DCE combine with TCE to contributeto this effect, their combined exposure of approximately 5,884 ppb approaches the exposure thatmade mice more susceptible to bacterial infection. Whether or not this increased susceptibility tobacterial infection might occur in people is speculative at this point because of our lack ofknowledge of how these chemicals might interact with each other in causing harmful effects.
Uncertainty exists for several reasons in ATSDR's evaluation of VOC exposure and thepossibility of harmful effects in adults and children. First, uncertainty exists in estimatingexposure, and these uncertainties are listed here:
- The estimates of exposure are based on two to three measurements of VOCs in privatewells in 1998 and 1999. ATSDR based its evaluation of estimated exposure on themaximum level detected and assumed that some people were exposed to these levels forup to 25 years. In fact, people may have been exposed to lower and higher levels over thecourse of many years.
- How long people were exposed to VOCs in private wells is not known. One resident haslived in Lockwood for over 40 years so if groundwater was contaminated 40 years ago,this resident might have been exposed for many decades. Adults and children also mayhave been exposed for a relatively short period, for instance, just a few years dependingupon when the groundwater was contaminated or when they moved into the residence andstarted using their private well for bathing.
- Many factors affect the air concentration of VOCs during and after showers and changingthese factors could increase or decrease the amount of exposure that would have occurredto VOCs because of volatilization from showers. For instance, ATSDR assumed astandard bathroom size of 10,000 liters, which affects the VOC air concentration reachedin the bathroom during a shower. A smaller bathroom would result in higher air levels,and a larger bathroom would result in lower air levels. ATSDR also assumed that 60% ofthe VOC would volatilize during the shower (Andelman 1985, McKone 1991). Ifsomeone takes a shorter shower and stays for a shorter time in the bathroom than whatATSDR assumed (i.e., a 10-minute shower and a 20-minute bathroom stay), theirexposure will be less. If someone takes a longer shower and stays longer in the bathroom,their exposure will be greater.
- Dermal absorption may be overestimated or underestimated. It may be that dermalabsorption is very small because showers take only 10 minutes and that amount of timemight not be sufficient for VOCs to reach equilibrium in crossing the skin barrier. On theother hand, the chlorinated VOCs might remove some of the lipid (i.e., fat) from the skinthus creating easy passages for VOCs to move through the skin more quickly. Inaddition, shorter and longer showers would decrease and increase dermal absorptionaccordingly.
- The indoor air measurements of VOCs, particularly PCE and TCE, might not reflect theconcentrations of those VOCs over the years. It could be that VOC measurements arelower in late spring, summer, and early fall because of higher air exchange rates in homes(for instance, from open doors and windows). Conversely, VOC measurements might behigher in winter because of lower air exchange rates in homes to conserve energy.
Second, uncertainties exist in comparing the estimated doses to animal and human studies anddeciding whether or not harmful effects might occur. These uncertainties are described in more detail here:
- The route of exposure can at times affect the toxicity of a chemical in two ways: achemical may cause a harmful effect by one route of exposure, for instance, inhalation,but not by another route of exposure, for instance, ingestion. In addition, the amount ofchemical that causes a harmful effect might be different based on the route of exposure. For instance, a chemical might be more toxic by inhalation than by ingestion, or vice-versa.
- When several routes of exposure occur at the same time, evaluating each route ofexposure separately may or may not be appropriate. As is the case here in Lockwood,people are exposed through inhalation and through the skin when they take a shower. The total amount of exposure is probably just as important as the individual route ofexposure. However, a decision needs to be made as to which toxicity studies should beused for comparison. Should inhalation studies be used or should dermal absorptionstudies be used. In the case of dermal absorption studies, such studies are frequently notavailable. Since this uncertainty exists about which route of exposure is most appropriate,ATSDR combined the dermal dose with the inhalation dose. The justification forcombining these two routes is because each exposure route distributes chemicalsthroughout the body first before reaching the liver, whereas, ingestion exposure firstdistributes absorbed chemicals to the liver. Therefore, it is reasonable to assume thatdermal absorption is more closely related to inhalation exposure than to ingestionexposure.
- Several of the chlorinated VOCs did not have sufficient chronic studies to determine thepossibility of harmful effects from chronic exposures. This hampered ATSDR's ability todecide if harmful effects might occur from many years of exposure.
- Totaling all the chlorinated VOCs to decide if harmful effects might occur may or maynot be appropriate. Very few controlled studies have been conducted looking at exposureto a mixture of chlorinated VOCs. Some occupational studies exist where exposure wasto a mixture of VOCs, but it is unclear which chemicals might be responsible for theeffects found in those studies.
In February 2002, MDEQ collected indoor air samples from the living space of 14 homes in theLomond Lane area. The maximum VOC levels are reported in Appendix B, Table 8. Sinceadults and children are no longer being exposed from other pathways, ATSDR reviewed thesedata from the winter of 2002 to determine if people should be concerned about breathing indoorair. ATSDR concluded that the current indoor air levels are safe and are not likely to causeharmful effects.
This conclusion was reached by comparing the current indoor air levels with ATSDR'sinhalation MRLs and with levels that are known to cause harmful effects. The current indoor airlevels of VOCs are below ATSDR's inhalation MRLs for non-cancerous effects, which meansthat non-cancerous harmful effects are unlikely. For instance, the maximum detected level ofPCE was 5.7 ppb. This level is below ATSDR's acute inhalation MRL of 200 ppb and thechronic inhalation MRL of 40 ppb for PCE. Because ATSDR's MRLs have built-in safetyfactors, the actual air level that causes harmful effects are much higher than 40 ppb and 200 ppb. Therefore, the levels detected in people's homes in Lomond Lane area are far below the levelsthat are known to cause harmful effects. A similar conclusion is reached for TCE since themaximum indoor level detected was 1.1 ppb, which is below the acute inhalation MRL of 2,000ppb and the intermediate MRL of 100 ppb. Since the detected levels are below ATSDR'sinhalation MRLs, harmful effects are unlikely.
In addition, ATSDR also compared the levels detected in indoor air in the Lomond Lane area toaverage background indoor air levels that are normally found in U.S. homes (See Appendix B,Table 8). The indoor air levels of the two major contaminants of concern (PCE and TCE) areabove the average background levels found in U.S. homes. For instance, PCE was found at 19.8ppb but the average background indoor levels of PCE is 0.6 ppb. Similarly, TCE was found at 14ppb while the average background level of TCE in U.S. homes is 0.4 ppb. Since these elevatedlevels of PCE and TCE were found in homes that are above the contaminated plume, it points toa soil-gas pathway for these homes.
In conversations with Dr. Lance Wallace, the EPA researcher who studied indoor air levels, hestated that these elevated levels of PCE and TCE were still within the range that one finds inindoor air of some U.S. homes. He stated that the elevated levels of PCE is not uncommon forsomeone who brings dry cleaning home. ATSDR is unsure at this time if the elevated levels ofthese two chemicals are due to the soil-gas pathway leaching chemicals into indoor air or to someother source in the house. It should be noted that current indoor levels of PCE were aboveaverage background levels in 6 of 14 homes tested. The remaining 8 homes had PCE levels that were below average background levels.
During its investigations, ATSDR staff members talked with residents at the Lockwood SolventsSite about their health concerns. What follows are the concerns residents raised and ATSDR'sresponse.
- The maximum contaminant level (MCL) for tetrachloroethene (PCE) in drinking water is5 ppb. Would prolonged exposure to tetrachloroethene in drinking water at 5 ppb resultin adverse health effects?
- When we used the well water for bathing and laundry, we often suffered from headaches,nausea, itchy skin, fatigue, coughing, high blood pressure and other ailments. Now thatwe no longer use the water, our symptoms have subsided. Could our symptoms havebeen caused by exposure to well water?
Response: Lifelong exposure to PCE at 5 ppb in drinking water is not likely to causeharmful effects. There are several reasons for this. First, the estimated amount ofexposure from drinking water with 5 ppb PCE is far below ATSDR's MRLs for PCE,which means that non-cancerous harmful effects are unlikely. Second, drinking waterstandards have built in safety factors such that PCE levels at or slightly exceeding thedrinking water standard do not mean that harmful effects are likely.
Response: A few adults and children in the Lockwood Solvents Site who used highlycontaminated well water were at risk of experiencing some harmful effects. The mostlikely symptoms are listed below:
- ability to respond as quickly to repeated stimuli,
- mild changes in eye-hand coordination,
- changes in the eye's perception of stimuli, and
- increased risk of cancer.
While VOCs can cause headaches, nausea, fatigue, and other symptoms at very highexposure levels, the level of exposure based on private well data collected from 1998 to2000 were not high enough to cause these effects. For instance, PCE exposure in humansat 216,000 ppb causes dizziness and sleepiness but does not cause those symptoms at106,000 ppb. These exposure levels can be compared to the estimated maximumconcentration in bathroom air at the Lockwood Solvents Site. For the highestcontaminated private wells, the estimated bathroom air for PCE from inhalation anddermal absorption is about 3,600 ppb and for total chlorinated VOCs is about 5,900 ppb. These levels are well below the 216,000 ppb that was shown to cause dizziness andsleepiness. Therefore, it seems unlikely that these more overt symptoms of dizziness andsleepiness are possible. A more detailed evaluation of health effects can be found in thesubsection Possible Harmful Effects from VOCs in Private Wells.
As described previously in this report, however, some uncertainty exists in estimatinghow much VOCs people are exposed to from taking a shower in contaminated water. Uncertainty also exists in making decisions about the possibility of harmful effectsoccurring. These uncertainties are described in more detail in the Uncertainty Analysissubsection
Response: MDEQ, EPA, and ATSDR jointly released a fact sheet in summer 2001answering residents' questions about what water uses are safe and not safe. Residentshad already been informed about not using their private well water for drinking andbathing so this fact sheet focused on other water uses.
The agencies provided the following answers in the fact sheet about safe water uses:
- It is safe to use private well water for watering yards, gardens, and houseplants.
- It is safe to use private well water to wash cars outdoors, although residentsshould use waterproof rubber gloves to avoid skin contact.
- It is not safe to use private well water for swimming pools, or for sprinklers thatchildren use for play.
- It is not safe to use private well water as water for pets and livestock.
The fact sheet released by the agencies can be found in Appendix F.
Response: A few adults and children in the Lockwood Solvents Site who used highlycontaminated well water for showering were at risk of experiencing some harmful effects. The most likely symptoms are listed below:
- ability to respond as quickly to repeated stimuli,
- mild changes in eye-hand coordination,
- changes in the eye's perception of stimuli, and
- increased risk of cancer.
As described previously in this report, however, some uncertainty exists in deciding whatharmful effects might occur in adults and children. This uncertainty exists for severalreasons. First, uncertainty exists in estimating how much VOCs people are exposed tofrom taking a shower in contaminated water since it is necessary to use mathematicalequations to estimate (A) how much of the VOCs evaporate from the shower water, (B)the VOC concentrations in bathroom air, (C) how much time someone spends taking ashower, and (D) how much time someone stays in the bathroom after a shower.
Second, uncertainty exists in combining exposure from inhalation and skin contact andthen using human and animals studies to decide the possibility of harmful effects. Thisuncertainty is described previously in more detail in the Uncertainty Analysis subsection.
Response: ATSDR suspects that some VOCs might be migrating from the groundwaterplume into some homes. There appears to be some correlation between high VOCcontamination in the groundwater and the higher VOC levels in indoor air of somehomes. The homes closest to the highest levels of groundwater contamination have thehighest indoor levels of PCE, TCE, and DCE. However, it is not certain if thecontaminated groundwater is the source of the chemicals found in the indoor air. It ispossible that other indoor sources, such as dry cleaned clothing or household cleaningagents and solvents, contributed to the elevated levels of VOCs found in the home.
Response: The answer to this question depends on the concentration of VOCs insomeone's private well and more specifically on the concentration of PCE. For VOClevels that are at or below the MCL, it is safe for children to play in the water as it is safefor them to drink and shower. However, a few private wells are highly contaminatedwith VOCs (specifically PCE), and it is not safe for children to swim in that water just asit is not safe for them to use that water to bathe or shower. While their inhalationexposure is probably less because they are outside, their dermal (skin) exposure isprobably greater because of their longer contact time with the water. While the VOCs willgradually evaporate from the pool water, no information exists to determine the VOClevels in pool water over time after the pool is filled; therefore, it is difficult to estimateexposure levels. To decide if water was safe or unsafe for use in kiddie pools, ATSDRused the concept of whether or not it was safe to bathe or shower with the water.
Response: Most of the harmful effects associated with showering in VOC-contaminatedwater (mild changes in eye-hand coordination, ability to respond as quickly to repeatedstimuli, changes in the eye's perception of stimuli) are not likely to be future healtheffects. If these effects occurred, they most likely occurred while using contaminatedwater and are unlikely to be lingering effects from exposure.
The health effect that might be a concern in the future from past exposure is liver cancer. Residents who showered in the most highly contaminated wells over many years shouldtalk to their physicians about their exposure and mention the increased possibility of livercancer. Residents and their personal physician can then decide what medical monitoringmight be appropriate in the future.
To ensure that the health of the nation's children is protected, ATSDR implemented an initiativerequiring that health assessments determine whether or not children are being exposed to site-related hazardous waste and whether or not the health of children might be affected.
This public health assessment reflects ATSDR's concern about protecting children's health fromtoxic chemicals in the environment. Children can be more sensitive to the effects of chemicalsbecause their exposure is greater or because their bodies are less capable of detoxifyingchemicals compared to adults.
Children breathe more air based on body weight when compared to adults and are thereforeprobably more sensitive to the effects of VOCs in well water when taking baths and showers. For this reason, ATSDR is concerned about exposure to children who took showers or bathed in water from the houses with the highest VOC contamination in well water.
ATSDR has established a registry of people in the U.S. who have been exposed totrichloroethylene (also known as TCE) in drinking water. Appendix G contains a press release from ATSDR that answers the following questions about the TCE subregistry:
- What is the TCE subregistry
- What is the registrant report
- What does it mean
- What happens now
- Where can I get more information
Basically, ATSDR identifies people who have been exposed to TCE for many years and invitesthem to answer a set of questions about their exposure and their self-reported health conditions. After this baseline survey, ATSDR requests the participants to periodically return a health surveyof the same or similar questions. ATSDR uses the results of these surveys to determine howoften certain self-reported health conditions occur in the TCE-exposed population and comparesthe results to a national control group of people who are answering the same or similar questions.
Appendix H contains a summary of the baseline survey of participants in ATSDR's TCEsubregistry. It summarizes the health conditions reported by the participants that were found tobe at greater frequency than a national comparison group. A description of the reportedconditions follows:
Rashes: Higher rates of "skin rashes, eczema, or skin allergies" were reported for bothmales and females in all age groups.
Speech Impairment: Higher rates were reported for males and females 9 years of age andyounger.
Hearing Impairment: Higher rates were reported for both males and females 9 years ofage and younger.
Stroke: Higher rates of "the effects of a stroke" were reported for both males and femalesfrom 35 through 54 years of age and 65 years of age and older.
Anemia and Blood Disorders: Higher rates were reported for males 9 years of age andyounger, 35 through 44 years, and 55 years of age and older, and females aged 18 through24 and 35 through 54 years of age.
Diabetes: Higher rates were reported for females 18 through 24 and 45 through 54 yearsof age.
Kidney Disease: Higher rates were reported among females from 55 through 64 years ofage.
Urinary Tract Disorders: Higher rates were reported among females in 0 through 9, 18through 44, and 55 and over age groups. Higher rates were seen in males from 18through 34 years of age.
ATSDR should point out that the National Exposure Registry for TCE is not a definitive healthstudy. That is, the findings of the registry cannot be used alone to determine if TCE is the causeof increased rates of symptoms or diseases found in the TCE-exposed population. The purposeof the TCE subregistry is to assist researchers in identifying health outcomes (symptoms anddiseases) that warrant consideration for future studies or activities.
In addition to this initial baseline report, which is based on the participants' first survey results,ATSDR has conducted follow-up surveys with the participants to determine their self-reportedhealth status. Appendix I contains a summary of the latest findings from the multiple surveysthat have taken place over the years. In short, ATSDR found that participants in the TCEsubregistry more frequently reported the following health conditions compared to participants inthe national survey:
- hearing impairment (after age 25 years);
- asthma, emphysema, or chronic bronchitis;
- arthritis, rheumatism, or other joint disorders; and
- other respiratory allergies or problems, such as hay fever.
However, these conditions are often self-diagnosed and medical care is not always sought forthem. Consequently, reporting rates might be affected by the restriction requiring confirmation by a health care provider, and this is reflected in the results.
Health education and promotion at ATSDR is a process of working with individuals, groups, andcommunities. Together we will plan and carry out activities that address the information andskill-building needs to help communities make decisions about health issues. We determine theinformation and skill-building needs of the community through discussions with affectedresidents. We also review available data and scientific literature on environmental health issuesof concern. Our goal is to learn the best ways to share information and health messages with the community.
From our discussions with residents, public health officials, and health care providers in theLockwood area, we learned that there is a need for health education on several topics. Theseinclude chemicals of concern, exposure information, terminology, and health effects. Futurediscussions with the community members will help us plan how to best address the health issuesthrough education and communication. We will consider workshops, articles in the local paper, fact sheets, etc.
In the past, the Lockwood Solvents Groundwater Plume Site was a public health threat becausesome adults and children were exposed to certain VOCs that might have caused harmful effects. Specifically, while taking showers, a few adults and children were exposed to levels of PCE thatmight have caused mild damage to their nervous system. Past exposure to PCE might havecaused mild changes in eye-hand coordination, changes in the ability to respond as quickly torepeated stimuli, and changes in the eye's perception of stimuli. These effects might haveoccurred while PCE exposure was occurring, but are not expected to be found in adults andchildren after exposure was stopped. In addition, adults and children who took showers usingwell water with high PCE levels might have an increased risk of cancer from PCE exposure.Some uncertainty exists in this conclusion, however, because of limitations in determining therisk of cancer for PCE. A few residents were also exposed to vinyl chloride that might haveincreased their risk of cancer. These conclusions are based on VOCs levels in private wells thatwere sampled in 1998 and 1999. VOC levels in prior years might have been higher or lower.
Most adults and children reportedly did not drink the water or use the water from their privatewells for cooking purposes; however, they did use the water to take showers and baths.Showering in VOC-contaminated water resulted in inhalation exposures when the VOCsevaporated from the water during the showers. In addition, adults and children were exposed toVOCs while showering or bathing because of absorption through the skin. Some adults andchildren also might have been exposed to VOCs via a soil-gas pathway.
Currently, all of the homes on the site either receive water from the municipal water supply or areserved by a well in which VOC contamination is below drinking water standards. Exposures tosite-related contaminants via well water have been eliminated for municipal water users. The soilgas pathway remains a potential exposure pathway by which residents might be exposed to site-related contaminants; however, this pathway is not expected to result in adverse health effectsbased on the current levels of exposure.
The source and extent of the groundwater contamination has not been determined. Sampling dataindicate that contaminant levels are approaching MCLs in several private wells in the site area.Additionally, off-site wells could become contaminated as the plume migrates; therefore,monitoring of the contaminant plume is necessary to prevent future exposures to adults andchildren.
- Implement procedures to stop exposure to contaminants in groundwater if levels ofcontamination in private wells exceed state or federal guidelines.
- Define the extent of the contaminant plume to determine whether other private wells in proximity to the plume have been affected, or could be affected in the future.
- Continue to monitor indoor air concentrations at selected residences, particularly ifconditions at the site change and during cold weather to confirm that indoor air levels ofVOCs are safe. Consider indoor air sampling of commercial businesses if it is determinedthat the building is over the groundwater contaminant plume.
- Continue to monitor contaminant levels in private wells of those residences that have not been supplied with an alternative water supply.
- Consider monitoring the private wells of businesses if it is determined they are in the path of the groundwater contaminant plume. Consider supplying businesses with bottled water for drinking purposes if their private well contains contaminant levels above an MCL.
- Develop and implement a health education plan with the Lockwood community and localhealth officials to meet information and skill-development needs about localenvironmental health issues involving the Lockwood Solvents Site.
- If their wells were highly contaminated with VOCs, residents should contact theirpersonal physician and show them at least the summary of this report. Residents and theirpersonal physician should then decide what medical monitoring is appropriate.
ATSDR plans to conduct health education to inform residents of the contents and conclusions ofthis public health assessment. Agency representatives will talk with residents to obtain their inputon developing an education plan that meets the residents' needs. This plan will involve workingwith residents to develop health education materials that answer their questions about theLockwood Solvents Site. The plan will include items such as when and where residents want tomeet, how to present information, who should present information, and follow-up activities.
The following ATSDR staff members were involved in the development of this report and other site-related activities:
Ms. Teresa Foster
Division of Health Assessment and Consultation
ATSDR, MS E-32
1600 Clifton Road
Atlanta, Georgia 30333
Mr. David Mellard, Ph.D.
Division of Health Assessment and Consultation
ATSDR, MS E-32
1600 Clifton Road
Atlanta, Georgia 30333
Mr. Dan Holcomb
Division of Health Assessment and Consultation
ATSDR, MS E-54
Atlanta, Georgia 30333
Mr. Dan Strausbaugh
ATSDR, Office of Regional Operations
Helena, Montana 59626
Ms. Kristina Larson
Division of Health Education and Promotion
ATSDR, MS E-42
Atlanta, Georgia 30333
Ms. Debra Joseph
Division of Health Assessment and Consultation
ATSDR, Community Involvement Branch
Atlanta, GA 30333
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2. A minimal risk level (or MRL) is a dose (in mg/kg/day) or concentration (in ppb) of a chemical below which non-cancerous harmful effects are not expected to occur. When sufficient scientific data are available, ATSDR develops MRLs for acute exposures (0 to 14 days), intermediate exposures (15 to 365 days), and chronic exposures (greater than 1 year). Exceeding an MRL does not mean that harmful effects are possible but rather that a more detailed evaluation is necessary to decide whether in fact harmful effects are possible. MRLs do not apply to cancer, which is evaluated using a different approach.