PETITIONED HEALTH CONSULTATION
Public Comment Release
Review of Groundwater Sampling Results from the Myrtle Grove Trailer Park Well System
MYRTLE GROVE TRAILER PARK
PLAQUEMINE, IBERVILLE PARISH, LOUISIANA
In August 2001, the Agency for Toxic Substances and Disease Registry (ATSDR) was petitioned for a public health assessment of the Myrtle Grove Trailer Park site in Iberville Parish, Plaquemine, Louisiana (Petition Letter 2001). Myrtle Grove residents are concerned about their past exposure to vinyl chloride-contaminated water. ATSDR accepted the request to evaluate the residents' concerns and notified the petitioner in October 2001 (ATSDR 2001b). This health consultation was developed to report the results of ATSDR's investigation.
ATSDR staff members reviewed available information on the MGTP water supply, summarized environmental sampling results, evaluated human exposures, and addressed community concerns. Until March 31, 200l, a well system on the property had been used to supply the 58 mobile homes with drinking water from the Plaquemine aquifer. A review of available water sampling data indicated that vinyl chloride levels had been above federal safe drinking water standards between 1997 and 2001. However, the levels of vinyl chloride that were detected in the well system would not be expected to produce adverse health effects in residents (either adults or children) who used the water for household and outdoor purposes. Levels of other contaminants detected in the well system were below levels of public health concern. A review of the health concerns reported by the residents indicated that their health concerns are not likely to be related to exposure to vinyl chloride or any other contaminant--or a combination of contaminants-- detected in the well water at the park.
Since March 2001, water samples have been collected from numerous wells surrounding the trailer park to define the extent of vinyl chloride contamination in the groundwater and help determine the source of the contaminant. The source (and there may be more than one) of the vinyl chloride is not yet known. ATSDR recommends continued monitoring of the vinyl chloride groundwater plume to better characterize the plume and determine its source. The U.S. Environmental Protection Agency (EPA) and the Louisiana Department of Environment Quality (LDEQ) are continuing to gather well data and other information needed to understand groundwater flow in the area. This type of information will aid in determining the source of the groundwater contamination.
ATSDR also recommends an evaluation of potential exposures related to groundwater for areas surrounding the trailer park that may be currently affected by the vinyl chloride groundwater plume. ATSDR is gathering available groundwater data and verifying exposure pathway information for this evaluation. Once the data gathering is completed, ATSDR will evaluate the additional data for public health significance and report the results of the evaluation in a separate health consultation.
Prior to the development of the Myrtle Grove Trailer Park (MGTP), the land was used for sugarcane production. The site is bounded by sugarcane fields to the west and north. The Green Acres housing addition abuts the site along the eastern border. To the south is Bayou Jacob Road and the Island Country Club community. Two manufacturing facilities, Dow Chemical and Shintech Incorporated, are located within two miles of the MGTP site. Figure 1, Appendix A, provides a site location map and Figure 2, Appendix A, provides demographic statistics for the area.
The Myrtle Grove Trailer Park was developed in the early 1980s. The well system that originally provided water to the park was located on south side of the site just west of the first mobile home. The well system consisted of a fenced concrete slab containing two well heads. Water from these two well heads was drawn from about 180 feet below ground surface in the Plaquemine aquifer. A 55-gallon drum containing chlorine (with an automatic feed system) was located at each well head before the water entered two large pressure tanks. The two pressure tanks then fed a common distribution pipe that provided water to the 58 trailer park residences (ATSDR 2001a).
The Louisiana Department of Health and Hospitals (LDHH) is required to conduct tests every 2 to 3 years on any drinking water well system that has more than 15 connections. During routine testing of the well system in February 2001, vinyl chloride levels were found to be above federal safe drinking water standards. Park residents were placed on city-supplied water (ATSDR 2001a). After the vinyl chloride detection in February 2001, LDHH performed a records review of their files for the MGTP well system. Vinyl chloride levels were above safe drinking water standards in November 1997 and September 1998.
Since becoming aware of the vinyl chloride groundwater plume, the Louisiana Department of Environmental Quality (LDEQ) has taken actions to assure that no one is drinking water from the aquifer in the area of contamination. The department performed a detailed reconnaissance of historical activities in the area. LDEQ identified numerous water wells in the Plaquemine area through discussions with long-time residents, door-to-door visits, public meetings, and calls to a LDEQ toll-free line. Although some wells exist in the area, none are currently used for drinking water. However, several wells within the vinyl chloride groundwater plume have recently been used or are being used by local businesses for sanitary purposes (as water supply for toilets and sinks), some wells supply water to ponds, and two wells are used for irrigating small gardens.
LDEQ and EPA sampled numerous wells in the Plaquemine aquifer to determine the source and extent of vinyl chloride contamination. Although many groundwater samples were collected and analyzed, the source of the vinyl chloride is not yet known. LDEQ and EPA are continuing to gather information and well data needed to improve the understanding of groundwater flow in the area. This information should help in efforts to determine the source of the groundwater contamination.
On August 21, 2001, ATSDR staff members had one-on-one visits with three Myrtle Grove homeowners. During these meetings, the homeowners expressed numerous health concerns including mild headaches, skin rashes and irritation, changes in skin pigment, numbness, high blood pressure, nose bleeds, stomach problems, nausea, asthma, miscarriages, behavior problems and learning disabilities in school-age children, and breast cancer. An open house meeting was held later that evening at the Louisiana Environmental Action Network (LEAN) office in Plaquemine, Louisiana. Approximately 40 residents of the Plaquemine area, several lawyers, and several reporters attended and asked ATSDR and EPA staff members questions about the MGTP site. During this meeting, ATSDR and EPA staff members also provided background information about each agency's involvement with the site.
During a conference call held in early December 2001 with MGTP representatives and representatives of LEAN, ATSDR was asked about available health care programs. ATSDR staff members outlined the programs potentially available for park residents. An outline of the available programs is provided in Appendix E, and the programs are also discussed in the Community Concerns Evaluation section of this document.
Exposure to water from the MGTP well water system stopped in March 2001. Park residents want to know whether their current health problems could be caused by their past exposure to the groundwater. In late December 2001, residents reported health problems that included developing lumps covering the body, severe coughing leading to nose bleeds, vomiting blood, blood in stool, and liver cancer.
On March 11, 2002, ATSDR staff visited the MGTP site to meet with the residents, tour the area, and gather data. During one-on-one meetings, residents again expressed concerns about skin rashes, liver cancer, and stomach problems. The residents also wanted information on how vinyl chloride moves through the body. They questioned whether vinyl chloride could cause genetic damage and lupus, whether arsenic was detected in the water, and whether the contamination could be responsible for rust-colored water that smells like sewage. During an MGTP organizational meeting held that evening at the LEAN office in Plaquemine, residents expressed concern about the effects of vinyl chloride exposure in combination with common household cleaning products. The residents also wanted to know if there were any studies on exposure to vinyl chloride in drinking water and whether park residents could be added to an ATSDR disease registry for vinyl chloride. Members of LEAN wanted to know if the agency had information on whether anyone else had ever been exposed to vinyl chloride in groundwater at the levels detected in the MGTP well system. LEAN members also expressed concerns about past and present vinyl chloride-contaminated groundwater exposures in other areas of Iberville Parish, specifically the bayou and rural River Road areas.
ATSDR's Division of Health Education and Promotion assisted in coordinating healthcare provider training for the Myrtle Grove area. On April 5, 2002, the Louisiana Department of Health and Hospitals (LDHH) sponsored the healthcare provider training event, and experts from Tulane University School of Public Health and Meharry Medical College presented the information to the local healthcare providers who attended. Training was provided in general environmental/occupational medicine. In addition, the training covered the potential effects of exposure to vinyl chloride. Continuing medical education credits were offered to the physicians. ATSDR information cards "Environmental Exposure History" and "Evaluating Environmental Exposures" were also given to those attending.
A public meeting, requested by the petitioner, was held in Plaquemine the day after the healthcare provider training. At this public meeting, held on Saturday, April 6, 2002, community members received information about ATSDR and were provided with a shortened version of the training given to the healthcare providers. Community members had the opportunity to ask questions and to provide input on future activities to be conducted in the Myrtle Grove area by ATSDR's Division of Health Education and Promotion.
In this section, ATSDR addresses the question of whether exposure to contaminants at the maximum concentrations detected at MGTP would result in adverse health effects. While the relative toxicity of a chemical is important, the human body's response to a chemical exposure is determined by several additional factors. Among these factors are the following:
- the concentration (how much) of the chemical the person was exposed to
- the amount of time the person was exposed (how long)
- the way the person was exposed (through breathing, eating, drinking, or direct contact with something containing the chemical).
Lifestyle factors (for example, occupation and personal habits) have a major impact on the likelihood, magnitude, and duration of exposure. Individual characteristics such as age, sex, nutritional status, overall health, and genetic constitution affect how a human body absorbs, distributes, metabolizes, and eliminates a contaminant. A unique combination of all these factors will determine the individual's physiologic response to a chemical contaminant and any adverse health effects the individual may suffer as a result of the chemical exposure.
ATSDR evaluates contaminants detected in environmental media at a site and determines whether an exposure to them has public health significance. ATSDR begins this evaluation by gathering reports that contain relevant environmental data for the site. These data are reviewed to determine if contaminant levels are above health-based comparison values. Health-based comparison values are estimates of the daily human exposure to a substance that are not likely to result in adverse, noncancer health effects over a specified duration of exposure. These values are developed for specific media (such as air, soil, and water) and for specific routes of exposure (such as breathing or touching). Health guideline values are sometimes derived from animal studies, with magnitudes of tens, hundreds, or thousands added as safety measures to be more protective of human health.
Comparison values and health guidelines represent conservative levels of safety and not thresholds of toxicity. Thus, although concentrations at or below a comparison value may reasonably be considered safe, concentrations above a comparison value will necessarily be harmful. Comparison values are intentionally designed to be much lower, usually by orders of magnitude, than the corresponding no-effect levels (or lowest-effect levels) determined in laboratory studies to ensure that even the most sensitive population (i.e., children, the elderly) are protected.
To determine whether people are being exposed to contaminants or whether they were exposed in the past or will be exposed in the future, ATSDR examines the path between a contaminant and a person or group of people who could be exposed. Completed exposure pathways have five required elements. ATSDR evaluates each possible pathway at a site to determine whether all five factors exist and people are being exposed, were exposed, or may be exposed in the future. These five factors or elements must exist for a person to be exposed to a contaminant:
(1) a source of contamination
(2) transport through an environmental medium
(3) a point of exposure
(4) a route of human exposure, and
(5) an exposed population.
ATSDR classifies exposure pathways in one of the following three categories.
- Completed Exposure Pathway. ATSDR calls a pathway "complete" if it is certain that people are exposed (or were exposed or will be exposed) to contaminated media. Completed pathways require that the five elements exist and indicate that exposure to the contaminant has occurred, is occurring, or will occur.
- Potential Exposure Pathway. Potential pathways are those in which at least one of the five elements is missing, but could exist. Potential pathways indicate that exposure to a contaminant could have occurred, could be occurring, or could occur in the future.
- Eliminated Exposure Pathway. In an eliminated exposure pathway, at least one of the five elements is missing and will never be present. From a human health perspective, pathways can be eliminated from further consideration if ATSDR is able to show that (1) an environmental medium is not contaminated or that (2) no one is exposed to contaminated media.
A completed exposure pathway to groundwater existed for residents (adults and children) of the Myrtle Grove Trailer Park. Approximately 600 people were exposed in the past when drinking, showering, bathing, cooking, washing dishes, or swimming in water supplied by the MGTP well system, potentially from sometime after April 1994 through March 2001. Routes of completed exposure in the past were ingestion (eating or drinking), inhalation (breathing), and dermal contact (skin contact). Since March 2001, park residents have been using water supplied by the city of Plaquemine distribution system. The MGTP well system is currently considered an eliminated exposure pathway because residents are no longer using this water. Table 1, Appendix B, provides information on the exposure pathways.
Samples collected from the MGTP well system were tested for water quality parameters including volatile organic compounds (VOCs). In April 1994, sampling and analysis of the well system did not detect vinyl chloride. Sampling of the well system in 1997, 1998, and 2001 indicated vinyl chloride levels ranging from 4.9 parts per billion (ppb) to 13.8 ppb. Results of the analysis of the vinyl chloride sampling are provided in Table 2 of Appendix B.
In addition to vinyl chloride, several other VOCs were detected in the well system. Although bromodichloromethane, bromoform, chlorodibromomethane, and chloroform were detected in the distribution pipe water; these chemicals are all typical byproducts of the chlorination process. Cis-1,2-dichloroethylene, which is a common breakdown product of trichloroethylene (TCE) and tetrachloroethylne (PCE), was also detected. However, TCE and PCE were not detected. Table 3 of Appendix B provides the sampling results for the chemicals detected.
The available data are limited because water samples were not collected from the MGTP well system prior to April 1994. ATSDR staff members reviewed available data and information on the chemicals detected in the following text.
Vinyl chloride is a colorless, flammable gas at normal temperatures, with a mild, sweet odor. It is a manufactured chemical that is used to make a common plastic product called polyvinyl chloride (PVC). PVC is used to make a variety of plastic products, including pipes, wire and cable coatings, and furniture and automobile upholstery. Vinyl chloride also results from the breakdown of other chemicals, such as trichloroethylene, tetrachloroethylene, and cis-1,2-dichloroethylene. Residents of Myrtle Grove Trailer Park were exposed to water contaminated with vinyl chloride by drinking the water (oral exposure) and by showering, bathing, cooking, washing dishes, and swimming in contaminated water (inhalation and dermal exposure).
After evaluating all of the available monitoring data, ATSDR concludes that none of the estimated drinking water exposures at MGTP were high enough to produce any of the known adverse health effects attributable to vinyl chloride, even after a lifetime of chronic oral exposure.
The maximum concentration of vinyl chloride recorded in drinking water at MGTP was 13.8 ppb. This would correspond to maximum doses of 1.38 micrograms per kilogram per day (µg/kg/day) for a 10-kilogram (kg) child drinking 1 liter of water per day (L/day) and 0.39 µg/kg/day for a 70-kg adult drinking 2 L/day. Although there are no drinking water studies of vinyl chloride exposure in humans, there are animal studies. Using animal studies, EPA derived a chronic oral reference dose (RfD) of 3 µg/kg/day. A reference dose is an estimate of daily exposure to a contaminant unlikely to cause noncancer adverse health effects. The doses received by adults and children drinking water provided by the MGTP well system are less than half of EPA's reference dose.
Vinyl chloride is a known human carcinogen under certain circumstances. Vinyl chloride has been consistently associated with elevated incidences of rare angiosarcomas of the liver in humans, but only by inhalation and only at the extremely high worker exposures that were once associated with certain job categories that no longer exist (Zocchetti 2001). This same form of liver cancer has also been produced experimentally in rats treated with chronic oral doses of 300 µg/kg/day. In humans, this dose would be numerically (if not biologically) equivalent to 10,500 ppb in drinking water for an adult drinking 2 L/day or 3,000 ppb for a child drinking 1 L/day, for several decades. These levels are over 650 times higher than the maximum recorded level of vinyl chloride in the MGTP well system and the residents were not exposed for decades.
Because no vinyl chloride was detected in wells at MGTP in 1994, detectable exposures may well have been limited to less than 8 years (i.e., from sometime after April 1994 to March 2001). During that time, daily fluid intake for the residents probably consisted of more than just the water from the tap at home. The fluid intake would have included water from other sources (for example, from school or work) and other beverages (such as soft drinks, fruit juices, and milk). These considerations would tend to reduce estimated exposures.
Based on the available data, it is unlikely that even the highest level of vinyl chloride detected in drinking water at MGTP would have been high enough to produce clinically adverse health effects in humans, even after a lifetime of chronic oral exposure (see Appendix C for further details). Nevertheless, because EPA's federal safe drinking water standards are legally enforceable, residents of MGTP were provided with an alternative source of drinking water as a prudent (that is, conservative) public health measure.
After evaluating all of the available sampling data, ATSDR considers that none of the estimated inhalation and dermal exposures to vinyl chloride at MGTP were high enough to produce any of the known adverse health effects attributable to vinyl chloride.
Residents inhaled vinyl chloride vapors in air, and their skin was exposed to vinyl chloride when showering, bathing, cooking, and washing dishes with water provided by the MGTP well system, as well as swimming in water provided by the well system. However, air data are not available for the kitchen and bathroom areas of the homes, nor for the outdoor area near the former privately owned pool. ATSDR used a one-compartment model to predict the residents' inhalation and dermal exposures from showering with the maximum detected level of vinyl chloride in their water. Based on a maximum water concentration of about 14 ppb, the estimated maximum concentration of vinyl chloride in air during showering would be 40 ppb (see Appendix D). Bathing, cooking, dishwashing, and swimming would result in much lower exposures to vinyl chloride than would showering (see Appendix D). Therefore, throughout the comparisons discussed in the following text, 40 ppb is used as the maximum site-specific concentration of vinyl chloride in air.
Vinyl chloride has neurotoxic properties at greater than 4,000 ppm (or 4,000,000 ppb) in air (ATSDR 1997b). The lowest known non-cancer effect level for vinyl chloride in air is 10,000 ppb for increased relative liver weight in rats treated 6 hours per day (hrs/day), 6 days per week (days/wk), for 6 months. The lowest known cancer effect level (CEL) for vinyl chloride in air is 5,000 ppb for mammary gland cancer in rats treated 4 hrs/day, 5 days/wk for 1 year (ATSDR 1997b). The maximum estimated inhalation exposures at MGTP (40 ppb) were 250 and 125 times lower than the lowest known effect levels in rats for noncancer and cancer effects.
Vinyl chloride is a known human carcinogen. Before effective engineering controls were applied, vinyl chloride sometimes caused angiosarcoma of the liver in workers in production plants who experienced prolonged, high-level inhalation exposure (usually hundreds or thousands of parts per million). This type of cancer is very rare in the general population. Even in workers with a history of occupational exposure to vinyl chloride, the incidence of angiosarcoma of the liver is relatively low, being confined almost exclusively to workers who used to manually clean the inner walls of large vinyl chloride reactor vessels, a job category which, thanks to closed-system technology, no longer exists. Elevated levels of angiosarcoma of the liver have not been seen in other individuals involved in the production or use of vinyl chloride. This low and limited occurrence of increased risk would seem to suggest that the carcinogenic potency of vinyl chloride is also relatively low (Williams and Weisburger 1991).
Based on the available data, ATSDR concludes that neither the magnitude nor the duration of dermal and inhalation exposures to vinyl chloride at MGTP was sufficient to produce any clinically adverse health effects.
The limited data available suggest that the vinyl chloride contamination entered the well system sometime after April 1994. Sampling of the well system in April 1994 did not detect vinyl chloride, but in November 1997, the levels were 4.9 ppb and 6.3 ppb. The levels generally increased in the following years to a maximum concentration of 13.8 ppb in March 2001. Therefore, there is no reason to believe that past undocumented exposures were any higher than the maximum detected concentration of vinyl chloride. Based on current toxicologic knowledge, it is unlikely that undocumented exposures in the past could have caused clinically significant health effects unless those exposures exceeded the maximum levels of vinyl chloride detected in water (13.8 ppb) or estimated in air (40 ppb) at MGTP by more than a hundredfold over an extended period of time. By comparison, estimated total exposures to vinyl chloride from all routes combined (drinking, showering, bathing, cooking, dishwashing, and swimming) at MGTP were most likely less than 2-3 times maximum drinking water exposures alone. (See Appendices C and D.) ATSDR concludes that the total vinyl chloride exposures at MGTP were not high enough to produce any of the known adverse health effects attributable to vinyl chloride.
The common chlorination byproducts bromodichloromethane (3.1 ppb-20.6 ppb), bromoform (16.0 ppb-16.9 ppb), chlorodibromomethane (28.6ppb-30.2 ppb), and chloroform (10.3ppb-13.0 ppb) were all detected in the MGTP well system distribution line. These levels are normal for chlorinated drinking water and would not be expected to cause adverse health effects (ATSDR 1989, ATSDR 1990, ATSDR 1997a). In addition, cis-1,2-dichloroethylene (1.0 ppb-2.16 ppb) was detected at levels below health-based comparison values. ATSDR determined that none of these VOCs pose a hazard to human health, even at the highest levels detected in the water at MGTP.
Because the individual contaminants detected at this site are present at levels that are below those that might be expected to result in adverse health effects, ATSDR considers that the combined effect of all these contaminants is also not likely to be of public health concern. This conclusion is based on studies which suggest that a mixture produces no adverse noncancer health effects in dosed animals when the components of that mixture are present at levels below their respective no-observed-adverse-effect levels (NOAELs), which are concentrations estimated to produce no adverse effects in animals treated separately with the individual chemicals (Feron et al., 1993; Jonker et al., 1993a; Jonker et al., 1993b; Jonker et al., 1990; Groton et al., 1991). Carcinogens exhibit thresholds in the laboratory, no less than do noncarcinogens (SOT, 1981; Williams and Weisbuirger, 1991; Cunningham, 1994). Therefore, it is likely that the previously stated principle regarding mixtures of noncarcinogens applies to mixtures of carcinogens as well. Because all measured levels of contaminants in the MGTP well system are below all known effect levels, ATSDR considers that the combined effect of all these contaminants is not likely to be of public health concern. (See Appendix F for additional information on chemical mixtures.) Nevertheless, ATSDR considers it prudent public health policy to reduce or eliminate wherever possible, excess exposure to substances which at higher concentrations can be toxic.
During meetings and conference calls, park residents expressed a variety of health problems they believe are caused by their past groundwater exposures to vinyl chloride. However, all substances detected in water supplied by the MGTP well system, including vinyl chloride, were present at concentrations below levels known to cause adverse health effects.
Because the health concerns expressed by the residents focused on vinyl chloride, ATSDR's responses in this section also focus on vinyl chloride. Most of the information concerning the known adverse health effects of vinyl chloride is from studies of vinyl chloride workers who breathed high levels in the past. These workplace levels are not typically found in either the workplace or the general environment today. The following text provides ATSDR's evaluation of each health concern that was reported by park residents with respect to the best toxicologic knowledge currently available.
- Mild headaches. Mild headaches are common, nonspecific symptoms that can be caused by many different chemical, physical, and/or biological stimuli, none of which affect everyone the same way at the same level of exposure. For example, some people get a headache when they breathe fresh air immediately after breathing very high levels of vinyl chloride (for example, higher than 1,000 ppm). In volunteers exposed for 5 minutes, twice a day, for 3 consecutive days, vinyl chloride caused headaches only at 20,000,000 ppb (ATSDR 1997b). This level is 500,000 times higher than the 40 ppb worst-case exposure level that MGTP residents might be exposed to while showering. Therefore, no such effects would be expected to occur from the maximum estimated exposures that may have occurred at MGTP. All concentrations of all substances detected in water at MGTP were below the lowest levels known to cause adverse health effects in animals or humans, including headaches.
- Skin rashes and irritation and changes in skin pigment. A worker who accidentally had escaping vinyl chloride vapor sprayed on his hands initially experienced numbness, then erythema (redness) and edema (swelling), before developing second degree burns (Harris 1953; ATSDR 1997b). Vinyl chloride is a liquid only under cold pressure. Thus, the dermal effects of vinyl chloride are specific not to the chemical itself, but to the rapid evaporation from the skin and resulting freezing of tissue. Similar dermal effects could not be caused by low parts per billion levels in water at room temperature. None of the other chemicals detected in the water at MGTP would be expected to cause such effects either, at the concentrations detected. All were present at concentrations below levels known to cause adverse health effects, including dermal effects.
- Numbness. In the previously mentioned case of a worker exposed by having liquid vinyl chloride vapor sprayed on his hands, the worker reported that his hands felt numb for a short time before marked swelling and redness developed. Some PVC production workers exposed to very high levels of vinyl chloride have also reported problems with the blood flow in their hands (Raynaud's phenomenon). Their fingers turn white and hurt when they go into the cold, and it may take a long time to recover when they go into a warm place. This condition occurred most frequently among workers who cleaned vinyl chloride reactor tanks, a job that involved some of the highest of historical exposures (ATSDR 1997b). No such effects would be expected to occur in response to the maximum estimated exposures that may have occurred at MGTP. All substances detected in the water at MGTP were present at concentrations below levels known to cause adverse effects, including numbness.
- High blood pressure. Relative to unexposed workers, there was an increased incidence and severity of high blood pressure and edema (preeclampsia) during pregnancy in female workers exposed to vinyl chloride (Bao et al. 1988; ATSDR 1997b). Note that hypertensive disorders occur in 1%-3% of all pregnancies and result in 20% of all maternal deaths (Maternal-Fetal Toxicology 1994). If these effects were, in fact, caused by vinyl chloride, the levels involved were probably between 10 ppm and 100 ppm (10,000 ppb and 100,000 ppb). No such effects would be expected to occur in response to the maximum estimated exposures that may have occurred at MGTP, because all substances detected in the water at MGTP were present at concentrations below levels known to cause adverse health effects, including high blood pressure.
- Stomach problems and nausea. Some workers breathing high levels of vinyl chloride reported stomach or gastrointestinal effects (ATSDR 1997b). Approximately 32% of the vinyl chloride workers examined by Lilis et al. (1975) reported a history of "gastritis, ulcers (gastric and duodenal) and upper gastrointestinal bleeding." Other symptoms reported by vinyl chloride workers included nausea, abdominal distension, and heartburn. Loss of appetite and nausea have been reported in Singapore workers exposed to 1 ppm-21 ppm vinyl chloride (Ho et al. 1991). However, these workers were selected on the basis of liver dysfunction. No such effects would be expected to occur in response to the maximum estimated exposures that may have occurred at MGTP, because all substances detected in the water at MGTP were present at concentrations below levels known to cause adverse health effects, including stomach problems and nausea.
- Asthma. Allergic diseases such as atopic dermatitis, rhinitis, and asthma are thought to result from a dysregulated immune response to commonly encountered antigens in genetically predisposed individuals (Lambrecht 2001). The most common substances causing allergic reactions in humans are certain drugs and plant and animal proteins, such as pollen, mold spores, dust mite feces, animal dander, venom, and foods. Cold dry air, stress, respiratory infections, and exercise can trigger attacks in some individuals (Meggs 2001). Perhaps 2% of the cases of asthma in the United States are occupational lung diseases in which an acquired hypersensitivity results in a minority of workers who become sensitized by exposures to high concentrations of mineral/vegetable dusts or reactive substances (for example, toluene) in air (Dean and Murray1991). Vinyl chloride, however, is not among these known, occupational, asthma-inducing agents. Reports regarding other respiratory effects in workers who are exposed to vinyl chloride in the workplace are contradictory. Several human studies found no increased incidence of respiratory disease among vinyl chloride workers, but several other studies found evidence of lung damage, e.g., an increased incidence of emphysema. Even the worst-case estimates of maximum total exposure to vinyl chloride at MGTP by all routes (inhalation, ingestion, and dermal contact) were below levels known to cause adverse health effects, including respiratory effects.
- Miscarriages. There is no credible evidence of a link between vinyl chloride and miscarriages in humans. In mice, exposures as high as 30,000 ppm (or 30,000,000 ppb), 6 hrs/day for 5 days had no effect on pre- or post implantation loss (ATSDR 1997b). No adverse health effects should be produced in response to the maximum estimated exposures at MGTP, because all substances detected in the water at MGTP were present at concentrations below all known effect levels.
- Behavior problems and learning disabilities in school-age children. There is no evidence of a link between vinyl chloride exposure and behavior problems and learning disabilities in school-age children. None of the contaminants detected in the water at MGTP were present at concentrations that would be expected to cause adverse health effects.
- Cancer, particularly cancer of the liver and breast. In previous decades, before the advent of better industrial hygiene practices, the incidence of an otherwise very rare form of liver cancer (hepatic angiosarcoma) was increased (but was still relatively low) in workers who manually cleaned vinyl chloride reaction vessels, a job category that no longer exists. The inhalation exposures associated with this job probably ran into the hundreds or thousands of parts per million. No other form of cancer has been consistently associated with high-level occupational exposures to vinyl chloride (ATSDR 1997b). Statistically significant increases in this same form of liver cancer have been produced experimentally in rats treated with chronic oral doses of 300 µg/kg/day and chronic inhalation doses greater than 100,000 ppb (ATSDR 1997b). The maximum estimated oral and inhalation doses to adult residents at MGTP were about 0.39 µg/kg/day and 40 ppb, respectively. In one inhalation study, a statistically significant increase of mammary tumors was produced in female rats at concentrations as low as 5,000 ppb for 52 weeks or about half the animals' lifetime. The maximum estimated inhalation exposures at Myrtle Grove were 40 ppb and only occurred during showering. (See Appendices C and D.) The total, worst-case exposures by all routes were several orders of magnitude lower than all known effect levels. No adverse health effects of either a cancer or noncancer nature would be expected to result from the maximum vinyl chloride exposures experienced by Myrtle Grove residents.
- Development of lumps covering the body. ATSDR is unaware of any vinyl chloride-associated symptoms in humans or animals that would fit this description.
- Severe coughing which leads to nose bleeds. Nose bleeds and coughing are nonspecific health effects that are not attributable to vinyl chloride exposure.
- Vomiting blood and blood in stool. Vinyl chloride exposure has not been associated with vomiting blood. In a study of workers exposed by inhalation to vinyl chloride at occupational levels, almost a third reported a history of "gastritis, ulcers (gastric and duodenal) and upper gastrointestinal bleeding" (ATSDR 1997b). None of these effects have been attributed to low-dose oral exposures to vinyl chloride. The maximum estimated exposures at MGTP were below levels known to cause adverse health effects.
In addition to addressing these specific health concerns of the Myrtle Grove residents, community residents asked ATSDR to address other issues related to vinyl chloride and the vinyl chloride groundwater plume. The following text outlines these issues.
- Vinyl chloride's movement through the body. Among other things, the time required for the body to eliminate foreign substances (such as vinyl chloride) from the body depends on the amount that entered the body in the first place. At the maximum estimated doses, most, if not all, of the vinyl chloride to which a resident was exposed on any given day at MGTP (the total exposure from ingestion, inhalation, and dermal contact) was distributed throughout the body in the bloodstream, metabolized to other more water-soluble substances in the liver, and probably excreted in the urine within 24 hours.
- Vinyl chloride's link to genetic damage and lupus. In the past, high occupational exposures (that is, tens, hundreds, or even thousands of parts per million in air) were associated with increased levels of generally reversible genetic damage and some specific mutations. However, the levels of exposure at MGTP are not expected to be associated with any detectable increase in genetic damage. The cause of lupus is unknown, but it appears to be an autoimmune disease. High titers of anti-DNA antibodies are almost specific for systemic lupus erythematosis and 90% of cases occur in women (The Merck Manual of Diagnosis & Therapy 1992). Vinyl chloride exposure is not a known risk factor for lupus.
- Arsenic in drinking water. Analysis of the water samples collected from the MGTP well system included metal analyses. Arsenic was not detected. The detection limit for arsenic was 20 ppb. Therefore, it is not known whether arsenic was in the water at levels below the detection limit. Several epidemiologic studies in the United States have not detected an increased frequency of arsenical skin cancer in populations drinking water containing 100-200 ppm arsenic (ATSDR 2000). Nevertheless, adverse health effects would not be expected from drinking water containing arsenic at levels of 20 ppb or less.
- Rust-colored water that smells like sewage. Iron was detected in the MGTP water system at levels ranging from 1.76 milligrams per liter (mg/L) to 2.63 mg/L. Water having an iron concentration of 0.05 mg/L may stain plumbing fixtures. Iron in excess of 1.0 mg/L can cause an unpleasant taste, and be noticeable in the taste of coffee or tea. If chlorine is added to the water system as a disinfectant to the water system, a sediment may form and cause the water to have a rusty brown cloudy effect (Salvato 1982). It is important to know that iron is an essential element needed for human health. The other compounds detected in the MGTP well system would not cause the water to be brown. The other compounds also do not have a sewage-like odor.
- Effects of vinyl chloride exposure in combination with common household cleaning products. At the levels detected in the MGTP well system, no combined effects would be expected. (See Appendix F, Chemical Mixtures.)
- Vinyl chloride drinking water studies. There are no studies--in either humans or animals--of the effects of drinking water containing vinyl chloride. Much higher concentrations are attainable in oil, so vinyl chloride is typically administered to experimental animals in oil. It has also been administered in feed. However, there also have never been reports of vinyl chloride poisoning through drinking water. The lowest level at which less-serious non-cancer effects have been seen in animals treated orally with vinyl chloride is 18 µg/kg/day for microscopic sites of cellular alteration in the livers of rats dosed throughout their lives with vinyl chloride in feed. The lowest published cancer effect is 300 µg/kg/day for angiosarcoma of the liver in rats treated throughout their lives with vinyl chloride in oil. In humans, numerically equivalent chronic (2 L/day) drinking water exposures for a 70-kg adult would be 630 ppb (for 18 µg/kg/day) and 10,500 ppb (for 300 µg/kg/day), respectively.
- ATSDR's National Exposure Registry. ATSDR established and maintains a National Exposure Registry of persons exposed to specific hazardous substances in the environment. The registry contains subregistries for specific compounds, and currently there are four active subregistries: trichloroethylene, trichloroethane, benzene, and dioxin. Vinyl chloride is not one of the compounds for which a subregistry has been established. Additional substances will be considered in the future when chemical selection is made for the subregistries An important purpose of the registry is to help scientists understand how long-term exposure to hazardous substances may affect human health.
- Prevalence of vinyl chloride in groundwater. As reported in ATSDR's Toxicological Profile on Vinyl Chloride, most drinking water wells do not contain vinyl chloride. In a 1982 survey, vinyl chloride was found in less than 1% of the 945 groundwater supplies tested in the United States. In this survey, the concentrations found in groundwater were up to 8.4 ppb, with a detection limit of 1 ppb. A separate report released in 1982 found concentrations of vinyl chloride in drinking water wells in New York State to be 50 ppb. Another report released in 1982 found that monitoring studies in nine states reported groundwater vinyl chloride concentrations at or below 380 ppb (ATSDR 1997b).
- Health care options for exposed residents. ATSDR does not have the legal authority to provide medical care or treatment to people who have been exposed to hazardous substances. Although the agency cannot provide medical care or treatment, sometimes the agency can provide medical monitoring in communities that have a significantly increased risk of disease from exposure to hazardous substances released into the environment. Because past exposures to contaminated groundwater at the MGTP site are unlikely to result in adverse health effects at the contaminant levels detected, medical monitoring is not indicated.
- Physician health education for area doctors and nurses. ATSDR's Division of Health Education and Promotion assisted in coordinating healthcare provider training for the Myrtle Grove area. Continuing medical education credits were offered to physicians in the Plaquemine area. Training was provided in general environmental/occupational medicine. In addition, the training covered the potential effects of exposure to vinyl chloride. Experts from Tulane University and Meharry Medical College presented the information to the local healthcare providers who attended. ATSDR information cards "Environmental Exposure History" and "Evaluating Environmental Exposures" were given to those attending.
- Community health education for exposed residents. A public meeting, requested by the petitioner, was held in Plaquemine on Saturday, April 6, 2002, the day after the healthcare provider training. At this public meeting, community members received information about ATSDR and were provided with a shortened version of the training given to the healthcare providers. Community members had the opportunity to ask questions and to provide input on future activities to be conducted in the Myrtle Grove area by the Division of Health Education and Promotion.
- Potential groundwater exposures throughout Iberville Parish. In addition to addressing the health concerns of Myrtle Grove residents, ATSDR was asked to address the health concerns of residents in other areas of Iberville Parish with potential exposures to the vinyl chloride groundwater plume. These health concerns include hair loss, learning problems in school-age children, and skin rashes. To date, ATSDR began the process of obtaining the available water data from wells identified within the vinyl chloride groundwater plume. ATSDR identified potential exposures from the use of ponds that are supplied by wells within the plume area. Some ponds are used for visual landscaping, like the golf course pond, but others may occasionally be used for swimming and fishing. In addition, water from several wells within the vinyl chloride groundwater plume area is being used or has recently been used by local businesses for sanitary purposes (to supply water for toilets and sinks). Potential exposures also exist for a few residents who use the vinyl chloride-contaminated groundwater for irrigating their gardens. At this time, with the exception of the MGTP well system, no additional wells have been identified as drinking water sources. ATSDR staff members plan to visit the area to further clarify these exposure pathways and gather necessary data. Once the data gathering process is completed, ATSDR will evaluate the information for public health significance and report the results in a separate health consultation document.
To address the residents' health care concerns, ATSDR staff members researched available health care options and found that several health care programs are potentially available for Myrtle Grove residents. First, the Louisiana Department of Health and Hospitals offers medical assistance to current and former residents of Myrtle Grove. This assistance includes an initial physical examination of people who have health problems associated with vinyl chloride exposure. The Louisiana Department of Health and Hospitals can also assist in accessing health care coverage such as Medicaid.
Second, the Health Resources and Services Administration (HRSA) has a health care facility in Appaloosa, Louisiana, that provides primary health care services to Louisiana residents with incomes 200% below the poverty level. HRSA also has a Louisiana Child Health Insurance Plan that allows for children to receive primary medical care if their parents' income is 200% below the poverty level. Third, the Southwest Center for Pediatric Environmental Health (known as the PED unit) can provide backup support to the medical community through telephone consultations to health care professionals. More information on these programs is available in Appendix E.
ATSDR recognizes that infants and children may be more vulnerable to exposures than adults in communities faced with contamination of their air, water, soil, or food. This vulnerability is a result of the following factors:
- Children are more likely to play outdoors and bring food into contaminated areas.
- Children are shorter, and more likely to breathe dust, soil, and heavy vapors close to the ground.
- Children are smaller, resulting in higher doses of chemical exposure per body weight.
- The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages.
Because children depend completely on adults for risk identification and management decisions, ATSDR is committed to evaluating their special interests at the Myrtle Grove Trailer Park site, as part of the ATSDR Child Health Initiative.
Children who are the most likely to be exposed to groundwater contaminants include the children living in the mobile homes and the children visiting the trailer park. However, based on all of the available data, past exposures to vinyl chloride in air and drinking water at MGTP were too low to produce any adverse health effects in children (see Section 3 and Appendix C). Assuming a 10-kg body weight and daily consumption of 1 liter of water containing 13.8 ppb vinyl chloride (the highest level detected at MGTP from 1997 to 2001), a child's exposure dose would be 1.38 µg/kg/day, or less than 8% of the lowest dose producing effects of marginal clinical significance in laboratory rodents treated throughout their entire lifetimes. However, actual exposures in children living at MGTP would be much lower still, because 1) the children would seldom drink only contaminated groundwater all day, 2) the well water that the children did drink would not have contained the maximum detected amount of vinyl chloride during the duration of the exposure period, and 3) the exposures to children at MGTP would have lasted for a relatively short period of time compared to the aforementioned lifetime exposures in laboratory rodents. All other substances detected in well water at MGTP were also present at levels too low to produce adverse health effects in exposed children.
The Myrtle Grove Trailer Park site poses no apparent public health hazard. Residents of the park were exposed to vinyl chloride in the past when drinking, showering, bathing, cooking, dishwashing, and swimming in water supplied by the MGTP well system, potentially from sometime after April 1994 through March 2001.The levels of vinyl chloride (4.9 ppb to 13.8 ppb) detected in the MGTP well system would not be expected to produce adverse health effects in residents (adults and children) who used the water for both household and outdoor purposes.
The common chlorination byproducts bromodichloromethane, bromoform, chloroform, and chlorodibromomethane were detected in the MGTP well system distribution line at levels that would not be expected to cause adverse health effects. In addition, cis-1,2-dichloroethylene was detected at levels below public health concern.
None of the health concerns reported by MGTP residents are likely to be the result of exposure to the levels of vinyl chloride or of any other contaminant detected in the water at MGTP, either separately or combined.
The source of the vinyl chloride plume has not been determined. Areas surrounding the MGTP site may currently be affected by the vinyl chloride groundwater plume. ATSDR will evaluate the potential for exposure in these areas in a separate health consultation.
- Continue monitoring the vinyl chloride groundwater plume to better characterize the plume and determine its source.
- Evaluate potential exposures to groundwater in areas surrounding the Myrtle Grove Trailer Park site that may be affected by the vinyl chloride groundwater plume.
The actions described in this section are designed to ensure that this health consultation identifies public health hazards and provides a plan of action to mitigate and prevent adverse health effects resulting from exposure to hazardous substances in the environment. EPA, the Louisiana Department of Environmental Quality (LDEQ), the Louisiana Department Health and Hospitals (LDHH), and ATSDR are working together to address issues regarding the vinyl chloride groundwater plume in Iberville Parish, Louisiana.
- In August 2001 and March 2002, ATSDR staff members visited the Myrtle Grove Trailer Park to meet with the residents, gather health concerns, and provide background information about the agency.
- Since March 2001, LDEQ has sampled numerous well locations, collected and analyzed many groundwater samples, participated in several public meetings, established a repository of information at the Plaquemine library, performed a detailed reconnaissance of historical activities in the area, and called in national groundwater experts for assistance.
- Since March 2001, LDEQ has taken actions to assure that no one is drinking water from the aquifer in the area of contamination. The department has identified numerous water wells in the North Plaquemine area through discussions with long-time residents, door-to-door visits, public meetings, and calls to a LDEQ toll-free line.
- Since March 2001, EPA has scaled up its oversight of the LDHH's implementation of the Safe Drinking Water Act program including a verification audit of LDHH's drinking water data and a review of LDHH's management system for data reporting.
- In December 2001, EPA sampled wells at numerous locations.
- In January 2002, EPA District Attorney activities included impaneling a special state grand jury to investigate possible criminal activity in connection with vinyl chloride contamination of groundwater in Plaquemine.
- On April 5, 2002, LDHH sponsored a healthcare training event. Professors from Tulane University School of Public Health and Meharry Medical College conducted a healthcare provider workshop to provide Plaquemine area doctors and nurses with training in environmental and occupational medicine and with information on the potential health effects associated with exposure to vinyl chloride.
- On April 6, 2002, ATSDR staff members held a public meeting to provide community members with healthcare information and information on ATSDR. The meeting provided an opportunity for community members to ask questions and provide input to the agency.
- LDEQ and EPA will continue to monitor and characterize the vinyl chloride groundwater plume.
- Local, state, and federal government agencies will continue to work together to address issues related to the vinyl chloride contamination of the Plaquemine aquifer.
- ATSDR will release a final health consultation on MGTP groundwater exposures which will address all comments the agency receives on the public comment version of this document.
- ATSDR plans to implement a psychosocial stress program for area residents. Additional healthcare provider training may be set up if needed.
- ATSDR will gather available groundwater data and verify exposure pathway information for areas surrounding the MGTP site that may currently be affected by the vinyl chloride groundwater plume. Once this data gathering task is completed, the agency will evaluate the additional data for public health significance in a separate health consultation.
Environmental Health Scientist:
Danielle M. Langmann, MS
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Frank C. Schnell, PhD, DABT
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Environmental Health Scientist:
Jason Sautner, MSCE
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Community Involvement Specialist:
Community Involvement Branch
Division of Health Assessment and Consultation
Health Education Specialist:
Division of Health Education and Promotion
LCDR Patrick Young
Office of Regional Operations
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Senior Regional Representative:
Office of Regional Operations
Associate Administrator for Urban Affairs:
Rueben C. Warren, DDS, DrPH
Office of Urban Affairs
Minority Health Program Manager/Environmental Toxicologist:
Stephanie Miles-Richardson, DVM, PhD
Office of Urban Affairs
Andelman JB. 1985. Inhalation exposure in the home to volatile organic contaminants of drinking water. The Science of the Total Environment. 47: 443-460.
Andelman JB. 1990a. Total Exposure to Volatile Organic Compounds in Potable Water. In: Significance and Treatment of Volatile Organic Compounds in Water Supplies; Chapter 20. Lewis Publishers. Chelsea, MI. 485-504.
Andelman JB, Giardino NJ, Marshall J, Esmen NA, Borrazzo JE, Davidson CI, Small MJ, and Wilkes C. 1990b. Exposure to volatile chemicals from indoor uses of water. pg 300-311 In: Total Exposure Assessment Methodology: A new horizon. Proceedings of the EPA/A&WMA Specialty Conference, Las Vegas, Nevada, November, 1989, Air & Waste Management Association, Pittsburg, PA,1990.
ATSDR 1989. Toxicological Profile for Bromodichloromethane. Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. December 1989.
ATSDR 1990. Toxicological Profile for Bromoform/Chlorodibromomethane. Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. December 1990.
ATSDR 1997a. Toxicological Profile for Chloroform (Update). Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. September 1997.
ATSDR 1997b. Toxicological Profile for Vinyl Chloride (Update). Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. September 1997.
ATSDR 2000. Toxicological Profile for Arsenic (Update). Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. September 2000.
ATSDR 2001a. ATSDR Record of Activity (AROA): Trip Report for August 21, 2001, to the Myrtle Grove Trailer Park petition site in Plaquemine, Louisiana. Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. August 21, 2001.
ATSDR 2001b. Letter from Robert C. Williams, P.E., DEE, Assistant Surgeon General, Director-Division of Health Assessment and Consultation, ATSDR, to the petitioner accepting the Myrtle Grove Trailer Park petition site for a Health Consultation. Atlanta, Georgia: U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. October 25, 2001.
Cunningham ML, Elwell MR, and Matthews HB. 1994. Relationship of carcinogenicity and cellular proliferation induced by mutagenic noncarcinogens vs carcinogens. Fundamental and Applied Toxicology, 23: 363-369.
Dean JH, and Murray MJ. 1991. Toxic Responses of the immune system. Chapter 9 in: Casarett and Doull's TOXICOLOGY: The Basic Science of Poisons. (Mary O Amdur, John Doull, and Curtis Klaassen, Editors.) Pergamon Press pp 127-200.
EPA 1986. Guidelines for Carcinogenic Risk Assessment. Washington: U.S. Environmental Protection Agency. Fed. Reg., 51: 33997-33998, September 24, 1986.
EPA 1989. Exposure Factors Handbook. Washington: U.S. Environmental Protection Agency. National Center for Environmental Research. EPA/600/8-89/043.
EPA 1996. Drinking water regulations and health advisories. Washington: U.S. Environmental Protection Agency. Office of Water. EPA 822-R-96-001.
Feron VJ, Jonker D, Groten JP, Horbach GJMJ, Cassee FR, Schoen ED, Opdam JJG. 1993. Combination technology: From challenge to reality. Toxicology Tribune 14: 1-3.
Feron VJ, Groten JP, van Zirge JA, Cassee FR, Jonker D, and van Bladeren PJ. 1995. Toxicity studies in rats of simple mixtures of chemicals with the same or different target organs. Toxicology Letters 82-83: 505-512.
Groton JP, Sinkeldam EJ, Luten JB, van Bladeren PJ. 1991. Interaction of dietary calcium, potassium, magnesium, manganese, copper, iron, zinc, and selenium with the accumulation and oral toxicity of cadmium in rats. Food and Chemical Toxicology 4: 249-258.
Groten JP, Schoen ED, van Bladeren PJ, Kuper CF, van Zorge JA, and Feron VJ. 1997. Subacute toxicity of a mixture of nine chemicals in rats: detecting interactive effects with a fractionated two-level factorial design. Fundamental and Applied Toxicology 36: 15-29.
Harris DK. 1953. Health problems in the manufacture and use of plastics. Br J Ind Med 10:255-268.
Hasegawa R, Miyata E, Futakuchi M, Hagiwara A, Nagao M, Sugimura T and Ito N. 1994. Synergistic enhancement of hepatic foci development by combined treatment of rats with 10 heterocyclic amines at low doses. Carcinogenesis 15: 1037-1041.
Ho SF, Phoon WH, Gan SL, et al. 1991. Persistent liver dysfunction among workers at a vinyl chloride monomer polymerization plant. J Soc Occup Med 41:(1):10-16.
IRIS 2002. Integrated Risk Information System, http://www.epa.gov/iris/index.html, an on-line database developed and maintained by the United States Environmental Protection Agency, File - Vinyl Chloride (CASRN 75-01-4) http://www.epa.gov/iris/subst/1001.htm.
Jo WK, Weisel CP, and Lioy PJ. 1988. Routes of Chloroform Exposure and Body Burden from Showering with Chlorinated Tap Water. Risk Analysis. 10(4) 575-580.
Jonker D, Woutersen RA, van Bladeren PJ, Til HP, Feron VJ. 1990. 4-week oral toxicity study of a combination of eight chemicals in rats: comparison with the toxicity of the individual compounds: Food and Chemical Toxicology; 28: 623-631.
Jonker D, Jones MA, van Bladeren PJ, Woutersen RA, Til HP, Feron VJ. 1993a. Acute 24 hour toxicity of a combination of four nephrotoxicants in rats compared with the toxicity of the individual compounds. Food and Chemical Toxicology 1993; 31: 45-52.
Jonker D, Woutersen RA, van Bladeren PJ, Til HP, Feron VJ. 1993b. Subacute (4-wk) oral toxicity of a combination of four nephrotoxicants in rats: comparison with the toxicity of the individual compounds. Food and Chemical Toxicology 31: 45-52.
Kerger B, and Paustenbach D. 2000. Exposure to 1,1,1-TCE Vapors in a Home Due to Contaminated Groundwater." Risk Anal. in press.
Kezic S, Mahieu K, Monster AC, de Wolff FA. 1997. Dermal Absorption of Vaporous and Liquid 2-Methoxyethanol and 2-Ethoxyethanol in Volunteers." Occup. Environ. Med. 54:38-43.
Lambrecht. 2001. Allergen uptake and presentation by dendritic cells. Curr Opin Allergy Clin Immunol 2001 Feb;1(1):51-9.
LDHH 2002. Louisiana Department of Health and Hospitals letter. Letter sent by Mike Dessauer, LDHH Engineering Tech 3, to Danielle Langmann, ATSDR Environmental Health Scientist, containing chemical sampling reports from the Myrtle Grove Trailer Park and Plaquemine Parish. January 29, 2002.
Lilis R, Anderson H, Nicholson WJ, et al. 1975. Prevalence of disease among vinyl chloride and polyvinyl chloride workers. Ann N Y Acad Sci 246:22-41.
Maltoni C, Lefemine G, Ciliberti A, et al. 1981. Carcinogenicity bioassays of vinyl chloride monomer: A model of risk assessment on an experimental basis. Environmental Health Perspectives 41: 3-29.
Maternal-Fetal Toxicology: A Clinician's Guide. Second Edition, Revised & Expanded, (Gideon Koren, Editor), Marcel Decker, Inc., New York, N.Y., 1994, pg 658.
Mattie DR, Bates GD Jr., Jepson GW, Fisher JW, McDougal JN. 1994. Determination of Skin-Air Partition Coefficients for Volatile Chemicals: Experimental Method and Applications. Fundam. Appl. Toxicol. 22:51.
Meggs WJ. 2001. Hypersensitivity Reactions. Chapter 26 in: Clinical Toxicology (Ford MD, Delaney KA, Ling LJ, and Erickson T, Editors) W.B. Saunders Company, New York, pp230-31.
Petition Letter 2001. Petition letter addressed to Dr. Henry Falk, MD, PhD, Assistant Administrator, ATSDR. Baton Rouge, Louisiana. August 3, 2001.
Salvato JA, P.E. 1982. Environmental Engineering and Sanitation, Third Edition 1982.
SOT 1981. Society of Toxicology. Re-evaluation of the ED01 Study. Fundamental and Applied Toxicology 1:27-128.
Takayama S, Hasagawa H, and Ohgaki O. 1989. Combination effects of forty carcinogens administered at low doses to male rats. Jpn. J. Cancer Res. 80: 732-736.
The Merck Manual of Diagnosis & Therapy. 1992. Vol. I. General Medicine. (Robert Berkow, MD, Editor-in-Chief). Merck Research Laboratories, Merck & Co., Inc., Rathway, NJ, pg 1140.
Til HP, Immel HR, Feron,VJ. 1983. Lifespan oral carcinogenicity study of vinyl chloride in rats. Final report. CIVO Institutes. TNO Report No. V 83.285/291099, TSCATS Document FYI-AX-0184-0353, Fiche No. 0353.
Til HP, Feron VJ, and Immel HR. 1991. Lifetime (149 week) oral carcinogenicity study of vinyl chloride in rats. Food Chemistry and Toxicology 29: 713-718.
Ward E, Boffetta P, Andersen A, Colin D, Comba P, Deddens JA, De Santis M, Engholm G, Hagmar L, Langard S, Lundberg I, McElvenny D, Pirastu R, Sali D, Simonato L. 2001. Update of the follow-up of mortality and cancer incidence among European workers employed in the vinyl chloride industry. Epidemiology 2001 Nov;12(6):710-8.
Williams GM, and Weisburger JH. 1991. Chemical Carcinogenesis. Chapter 5 in: Casarett and Doull's Toxicology: the Basic Science of Poisons. Fourth Edition (Mary O. Amdur, John Doull, Curtis D. Klaassen, Editors). Pergamon Press, New York, NY.
Williams PRD, Scott PK, Sheehan PJ, and Paustenbach DJ. 2000. A Probabilistic Assessment of Household Exposures to MTBE in California Drinking Water. Human and Ecological Risk Assessment. 6(5): 827-849.
Zocchetti C. 2001. Liver angiosarcoma in humans: Epidemiological considerations, Med Lav 2001 Jan-Feb 92(1):39-53 (Italian). An English abstract of this review article is available on-line at http://www.ncbi.nlm.nih.gov/entrez/.