Appendix D
Review of Other Chemical Contaminants of Concern

Chapter 2 identified seven contaminants of the water supply at Camp Lejeune that the committee judged as warranting further attention in addition to trichloroethylene and perchloroethylene: 1,2-dichloroethylene (1,2-DCE; cis- and trans-forms), 1,1-dichloroethylene (1, 1-DCE), benzene, methylene chloride (MC), toluene, and vinyl chloride (VC). (Information about the detection of these chemicals is presented in Chapter 2 and Appendix C.) The committee used comprehensive reviews performed by other organizations and agencies to compile the following overview of the potential health effects of those contaminants.

1,2-DICHLOROETHYLENE

The health effects of 1,2-DCE were reviewed by ATSDR (1996). 1,2-DCE is used to produce solvents and in chemical mixtures. There are two forms (isomers) of 1,2-DCE: cis-1,2-DCE, and trans-1,2-DCE. The two forms are sometimes present as a mixture. 1,2-DCE evaporates rapidly into air. Most 1,2-DCE in the soil surface or bodies of water will evaporate into air, and it can travel through soil or dissolve in water in soil. It is possible that it can contaminate groundwater. There is a slight chance that 1,2-DCE will break down into VC, which is believed to be more toxic than 1,2-DCE. One can be exposed by breathing 1,2-DCE that has leaked from hazardous-waste sites and landfills; by drinking contaminated tap water or breathing vapors from contaminated water while cooking, bathing, or washing dishes; by breathing it; by touching it; or by touching contaminated materials in the workplace. The most important effects of 1,2-DCE exposure are hematologic (such as a decrease in the number of red blood cells) and hepatic. Clinical symptoms that have been reported in humans exposed to 1,2-DCE at high concentration in air include nausea, drowsiness, fatigue, intracranial pressure, and ocular irritation. One fatality has been reported. No information is available on oral toxicity of 1,2-DCE in humans. No information is available on the relative toxicities of cis- and trans-1,2-DCE in humans. A variety of genotoxicity tests have been performed on 1,2-DCE. The predominant results are negative, and no carcinogenicity studies were found in the literature. EPA has determined that cis-1,2-DCE is not classifiable as to human carcinogenicity. No EPA cancer classification of trans-1,2-DCE is available. Specific effects of 1,2-DCE in animals are discussed below.

Hepatic Toxicity

Subchronic exposure to trans-1,2-DCE in drinking water (17-452 mg/kg per day) has caused biochemical changes in the livers of mice (Barnes et al. 1985). Both sexes had increased glucose concentrations, and females had decreased serum glutamic-pyruvic transaminase, serum glutamic-oxaloacetic



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 258
Appendix D Review of Other Chemical Contaminants of Concern Chapter 2 identified seven contaminants of the water supply at Camp Lejeune that the committee judged as warranting further attention in addition to trichloroethylene and perchloroethylene: 1,2- dichloroethylene (1,2-DCE; cis- and trans-forms), 1,1-dichloroethylene (1, 1-DCE), benzene, methylene chloride (MC), toluene, and vinyl chloride (VC). (Information about the detection of these chemicals is presented in Chapter 2 and Appendix C.) The committee used comprehensive reviews performed by other organizations and agencies to compile the following overview of the potential health effects of those con- taminants. 1,2-DICHLOROETHYLENE The health effects of 1,2-DCE were reviewed by ATSDR (1996). 1,2-DCE is used to produce solvents and in chemical mixtures. There are two forms (isomers) of 1,2-DCE: cis-1,2-DCE, and trans- 1,2-DCE. The two forms are sometimes present as a mixture. 1,2-DCE evaporates rapidly into air. Most 1,2-DCE in the soil surface or bodies of water will evaporate into air, and it can travel through soil or dis- solve in water in soil. It is possible that it can contaminate groundwater. There is a slight chance that 1,2- DCE will break down into VC, which is believed to be more toxic than 1,2-DCE. One can be exposed by breathing 1,2-DCE that has leaked from hazardous-waste sites and landfills; by drinking contaminated tap water or breathing vapors from contaminated water while cooking, bathing, or washing dishes; by breathing it; by touching it; or by touching contaminated materials in the workplace. The most important effects of 1,2-DCE exposure are hematologic (such as a decrease in the number of red blood cells) and hepatic. Clinical symptoms that have been reported in humans exposed to 1,2-DCE at high concentration in air include nausea, drowsiness, fatigue, intracranial pressure, and ocular irritation. One fatality has been reported. No information is available on oral toxicity of 1,2-DCE in humans. No information is available on the relative toxicities of cis- and trans-1,2-DCE in humans. A variety of genotoxicity tests have been performed on 1,2-DCE. The predominant results are negative, and no carcinogenicity studies were found in the literature. EPA has determined that cis-1,2-DCE is not classifiable as to human carcinogenicity. No EPA cancer classification of trans-1,2-DCE is available. Specific effects of 1,2-DCE in animals are discussed below. Hepatic Toxicity Subchronic exposure to trans-1,2-DCE in drinking water (17-452 mg/kg per day) has caused bio- chemical changes in the livers of mice (Barnes et al. 1985). Both sexes had increased glucose concentra- tions, and females had decreased serum glutamic-pyruvic transaminase, serum glutamic-oxaloacetic 258

OCR for page 258
Appendix D 259 transaminase, and aniline hydroxylase activity at all doses. Males had significantly decreased glutathione at the highest dose. In studies with rats, increased relative hepatic weights were observed with cis-1,2- DCE at 32 mg/kg per day and higher (McCauley et al. 1995). Variable changes in hepatic enzyme con- centrations were seen, but no histopathologic lesions of the liver. A study of trans-1,2-DCE administered to rats in microcapsules for 14 weeks reported increased hepatic weights in females but not males at 395 mg/kg per day (NTP 2002c). No significant alterations in clinical-chemistry measures were found. In an inhalation study, fatty degeneration of liver lobules was observed in female rats exposed to trans-1,2-DCE at 200 ppm for 8 or 16 weeks (Freundt et al. 1977). Renal Toxicity There is little clinical or histologic evidence of renal toxicity in experimental studies of 1,2-DCE (ATSDR 1996). A recent 14-week study of trans-1,2-DCE reported significantly reduced absolute renal weights in male rats at 1,540 mg/kg per day (NTP 2002c) but no gross or microscopic lesions. Pulmonary Toxicity With the exception of some effects on the lungs after lethal doses of trans-1,2-DCE, experimental studies of DCE isomers have yielded little clinical or histologic evidence of pulmonary toxicity (ATSDR 1996). Reproductive Toxicity One study of pregnant rats exposed by inhalation to trans-1,2-DCE at 6,000 or 12,000 ppm found a significant increase in the mean number of resorptions per litter (Hurtt et al. 1993), but the authors noted that the value was within the range of historical control values; maternal toxicity was observed. The Na- tional Toxicology Program (NTP 2002c) reported no significant changes in sperm motility or vaginal cy- tology in rats or mice fed microencapsulated trans-1,2-DCE at doses as high as 8,065 mg/kg per day for 14 weeks. Developmental Toxicity Hurtt et al. (1993) reported significantly reduced mean combined and female fetal weights in rats exposed to trans-1,2-DCE by inhalation during pregnancy at 12,000 ppm. The dams had frank maternal toxicity, as evidenced by reduced food consumption and reduced weight gain. Neurotoxicity Several studies have reported central nervous system (CNS) depression in rats after exposure to cis-1,2-DCE at 878 mg/kg per day (McCauley et al. 1995) or to either isomer of 1,2-DCE at lethal doses (Barnes et al. 1985; McCauley et al. 1995). After inhalation exposure, experimental animals have exhib- ited lethargy, behavioral changes, and other neurologic effects (ATSDR 1996), but the significance of the changes is unclear. A functional observational battery performed on mice and rats given microencapsu- lated trans-1,2-DCE in their feed at up to 8,065 mg/kg per day for 14 weeks found no evidence of CNS depression (NTP 2002c).

OCR for page 258
Contaminated Water Supplies at Camp Lejeune—Assessing Potential Health Effects 260 Immunotoxicity In studies of mice given trans-1,2-DCE orally at 224 mg/kg per day, an increase in leukocyte counts and a decrease in relative thymus weight were found in females, but no changes in cell-mediated or humoral immunity were observed (Barnes et al. 1985; Shopp et al. 1985). However, in one study, male mice treated with trans-1,2-DCE at 17-387 mg/kg per day exhibited decreased spleen-cell production of antibody against sheep erythrocytes, which did not result in a functional effect on the humoral immune system (Shopp et al. 1985). An inhalation-exposure study of trans-1,2-DCE by Freundt et al. (1977) re- ported fatty degeneration of Kupffer cells, decreased leukocyte counts, and pulmonary infiltration at 200 ppm and greater. Hematopoietic Toxicity Female rats exposed to cis-1,2-DCE exhibited decreased hemoglobin concentrations, red blood cell counts, and hematocrit values at 98 mg/kg per day for 90 days (McCauley et al. 1995) but not at lower doses, and no statistically significant effects were observed in male rats. Other studies have re- ported no hematologic effects in rats or mice after oral exposure to trans-1,2-DCE at up to 3,114 mg/kg per day for 90 days (Barnes et al. 1985; Hayes et al. 1987). In a more recent 14-week study, the NTP (2002c) reported mild decreases in hematocrit values, hemoglobin concentrations, and red blood cell counts in rats fed microcapsules containing trans-1,2-DCE at 380 mg/kg per day for males and 1,580 mg/kg per day for females. Mice similarly exposed did not have those changes. Genotoxicity Genotoxicity studies of 1,2-DCE have had predominantly negative results (ATSDR 1996; NTP 2002c). Both isomers were negative in mutagenicity assays with bacteria and chromosomal-aberration tests with Chinese hamster cells. Mixed results have been reported with respect to chromosomal effects in mammalian systems (ATSDR 1996; NTP 2002c). Negative results were reported in a peripheral-blood micronucleus test performed with mice fed microencapsulated trans-1,2-DCE for 14 weeks (NTP 2002c). Cancer No cancer bioassays of either isomer of 1,2-DCE have been performed. 1,1-DICHLOROETHYLENE The health effects of 1,1-DCE, also known as vinylidene chloride, were reviewed by the Agency for Toxic Substances and Disease Registry (ATSDR 1994), the International Agency for Research on Cancer (IARC 1999a), and the U.S. Environment Protection Agency (EPA 2002). 1,1-DCE is an indus- trial chemical not found naturally in the environment. It is used to make plastics (such as flexible films for wrapping food and packaging materials), to make flame-retardant coatings for fiber and carpet backings, and in piping, coating for steel pipes, and adhesives. 1,1-DCE evaporates quickly from water and soil, breaks down slowly in water, and is slowly transformed to other, less harmful chemicals in soil. One may be exposed to 1,1-DCE through employment in industries that make or use 1,1-DCE, through food that is wrapped in plastic that contains 1,1-DCE, through drinking water from the small percentage of supplies that contain 1,1-DCE, and through air near factories or hazardous-waste sites. It has been used in the past

OCR for page 258
Appendix D 261 as a gaseous anesthetic agent; its use as an anesthetic agent was discontinued after it was discovered that it induced cardiac arrhythmia at anesthetic doses. Inhalation of high concentrations of 1,1-DCE is known to cause reversible nervous system impairment. Workers exposed to 1,1-DCE have reported a loss in he- patic function, but other chemicals were present. Specific effects of 1,1-DCE in animals are discussed briefly below. Hepatic Toxicity Acute doses of 1,1-DCE administered orally to rats at 25-100 mg/kg per day induced hepatic tox- icity, including alterations in hepatic enzymes indicative of damage or dysfunction and histopathologic evidence of damage (ATSDR 1994). Gavage studies of more prolonged exposure to 1,1-DCE (13 weeks) reported hepatic necrosis in male mice exposed at 250 mg/kg per day and in female mice at 5 mg/kg per day (NTP 1982). Similarly exposed rats had chronic hepatic inflammation at a dose of 250 mg/kg per day. Drinking-water and feed studies have reported little or milder evidence of hepatic toxicity. For example, Quast et al. (1983) reported no histopathologic changes in the livers of dogs exposed to 1,1-DCE in drink- ing water at 25 mg/kg per day for 97 days. In 2-year exposure studies with rats, only mild hepatocellular changes were observed at doses of 6-30 mg/kg per day (Rampy et al. 1977; Quast et al. 1983). Inhalation-exposure studies have reported similar evidence of hepatic toxicity in rats and mice (ATSDR 1994). After some of the longer exposures, changes observed at 25 ppm included cytoplasmic vacuolation (ATSDR 1994) and fatty infiltration of the liver (Quast et al. 1986), and at 125 ppm, centri- lobular fatty degeneration and hepatic necrosis (ATSDR 1994). Food intake appears to affect the hepatic toxicity of 1,1-DCE: greater effects have been observed in fasted rats in both oral and inhalation studies (ATSDR 1994). Renal Toxicity Several types of renal effect have been reported in experimental animals exposed to 1,1-DCE orally and by inhalation. For example, single oral doses of 1,1-DCE at 200 mg/kg or greater caused histo- pathologic changes in the kidneys of rats (ATSDR 1994). However, no renal effects were observed in experimental animals exposed at 30 mg/kg per day or less in chronic-exposure studies (Rampy et al. 1977; Quast et al. 1983). In acute-inhalation studies, renal effects have included enzyme changes, hemoglobinuria, in- creased kidney weight, and tubular swelling, degeneration, and necrosis at concentrations as low as 50 ppm in rats and 10 ppm in mice (ATSDR 1994). In toxicity studies of longer duration (52 weeks), severe renal effects have been observed in mice at 10-25 ppm (Maltoni et al. 1985) but not in rats (Maltoni et al. 1985; Quast et al. 1986). The renal toxicity of 1,1-DCE appears to be related to sex-specific expression of CYP2E1 in male mice (EPA 2002). One proposed mechanism of renal toxicity is the formation of cytotoxic intermediates from CYP2E1 activity in the kidneys. Another possible mechanism is the formation of S-conjugates that are metabolized by β-lyase in the proximal renal tubules and yield products that interact with macromole- cules (ATSDR 1994; EPA 2002). Pulmonary Toxicity Acute inhalation exposure to 1,1-DCE has produced swelling, edema, and congestion of the lungs of rodents at 500-15,000 ppm and in some species at concentrations as low as 20 ppm (ATSDR 1994). One acute oral study of 1,1-DCE (100 mg/kg) found pulmonary injury in mice (Forkert and Reynolds 1982). Clara cells are especially targeted in the lungs of mice (Forkert et al. 1986). In longer-term inhala-

OCR for page 258
Contaminated Water Supplies at Camp Lejeune—Assessing Potential Health Effects 262 tion-exposure studies, no histopathologic changes in the lungs or respiratory system were observed in several test species at 100 ppm (Prendergast et al. 1967; Quast et al. 1986). Reproductive Toxicity No evidence of reproductive toxicity was found in a three-generation study of rats exposed to 1,1- DCE in drinking water at up to 200 ppm (Nitschke et al. 1983). Similarly, no effects were found in repro- ductive studies in male rats exposed to 1,1-DCE by inhalation at up to 50 ppm (Anderson et al. 1977; ATSDR 1994). Developmental Toxicity Murray et al. (1979) studied the effects of inhaled 1,1-DCE on pregnant rats. Maternal and em- bryo toxicity was observed in rats exposed during gestation at 80 ppm or greater and in rabbits at 160 ppm, but there was no evidence of teratogenicity in either species. A study of 1,1-DCE administered in the drinking water of pregnant rats at 200 ppm found no evidence of maternal or fetal toxicity or terato- genicity (Murray et al. 1979). In another study, 1,1-DCE was administered to rats in drinking water before mating and/or during gestation (Dawson et al. 1993). A significant increase in congenital cardiac malformations was observed in the fetuses of rats treated before mating and during gestation at a drinking-water concentration of 0.15 or 100 ppm, but a dose-response relationship was not demonstrated. However, a three-generation study of rats exposed to 1,1-DCE in drinking water at up to 200 ppm did not find cardiac changes (Nitschke et al. 1983). One study reported a significant increase in the mean number of mouse fetuses with an unossified incus and with incompletely ossified sternebrae at a drinking-water concentration of 15 ppm (EPA 2002). Other evidence of developmental toxicity was observed at higher concentrations, but frank maternal tox- icity was also observed at those concentrations. Neurotoxicity Like other organic solvents, 1,1-DCE at high concentrations has a narcotic effect on experimental animals (ATSDR 1994). In general toxicology studies, there have been no reports of neurologic effects of 1,1-DCE after oral or inhalation exposure, but these studies were not designed specifically to evaluate neurologic effects. Immunotoxicity Ban et al. (2003) exposed mice to 1,1-DCE by inhalation at 5-15 ppm and tested systemic and lo- cal immune response. IgM response in the lymph nodes to challenge with sheep red blood cells was in- creased, and the highest exposure provoked a similar response in the spleen. A significant increase in the release of interferon-gamma was found in lymph node cultures but the increase in spleen cell cultures was smaller. The investigators concluded that lung-associated lymph nodes could be sensitive targets for in- haled 1,1-DCE. Hematopoietic Toxicity No significant hematologic changes have been reported in drinking-water studies of 1,1-DCE in

OCR for page 258
Appendix D 263 dogs exposed at 25 mg/kg per day for 97 days (Quast et al. 1983) or in rats exposed at 30 mg/kg per day for 2 years (Rampy et al. 1977; Quast et al. 1983). No evidence of hematotoxicity was observed in inhala- tion studies with rats and mice exposed at 55-75 ppm for 1 year or more (Lee et al. 1977; Quast et al. 1986). Genotoxicity 1,1-DCE has been shown to be mutagenic, to induce chromosomal aberrations and sister- chromatid exchanges in vitro, and to cause DNA damage in vivo (ATSDR 1994; EPA 2002). In most cases, metabolic activation was required to produce the results. Cancer A number of chronic bioassays of oral and inhaled 1,1-DCE have been performed in rodents (ATSDR 1994; EPA 2002; Roberts et al. 2002). Only one inhalation study has shown evidence of car- cinogenicity (Maltoni et al. 1985); male mice exposed at 25 ppm had an increased incidence of renal ade- nocarcinomas. IARC judges 1,1-DCE as not classifiable with respect to human carcinogenicity (IARC 1987, 1999a). BENZENE Benzene, also known as benzol, has industrial and natural sources. First discovered and isolated from coal tar in the 1800s, benzene is made mostly from petroleum today and ranks in the top 20 in pro- duction volume among chemicals produced in the United States. Other sources of benzene include gas emissions from volcanoes, forest fires, gasoline, and cigarette smoke. Benzene is widely distributed in the environment, and low-level inhalation over long periods is of most concern. People employed in indus- tries that make or use benzene or products that contain it are probably exposed to the highest concentra- tions of atmospheric benzene. People with benzene-contaminated tap water can be exposed from drinking the water or eating foods prepared with it; by inhalation during showering, bathing, and cooking; and through dermal contact during showering and bathing. Benzene is a well-studied chemical and has been the subject of several comprehensive reviews and risk assessments (IARC 1982, 1987; EPA 1998b, 2002; ATSDR 2007). It is well established in those reviews that benzene is associated with effects on the hematologic, immune, and nervous systems. Evi- dence of the effects is found in reports of controlled animal experiments (Gill et al. 1980; Rozen et al. 1984; Cronkite et al. 1985, 1989; Rosenthal and Snyder 1985; Molnar et al. 1986) and in the epidemi- ologic literature, especially reports of occupational studies of benzene exposure (Srbova et al. 1950; Yin et al. 1987a; Kraut et al. 1988; Rothman et al. 1996; Lan et al. 2004). There is agreement in the scientific community that benzene is a human carcinogen (IARC 1987; EPA 1998b; NTP 2005; ATSDR 2007). Inhalation studies of rodents show that benzene causes cancer in multiple tissues, and there is strong evidence of lymphoid tumors in mice (Snyder et al. 1980, 1984, 1988; Cronkite et al. 1984, 1985, 1989; Maltoni et al. 1989; Farris et al. 1993). Acute myelogenous leukemia is the predominant cancer found in humans exposed to benzene and has been documented in studies of workers exposed to benzene in rubber hydrochloride manufacturing plants (Rinsky et al. 1981, 1987) and in factories in China (Yin et al. 1987b, 1989, 1996; Hayes et al. 1996, 1997). Most epidemiologic studies have also found an increased risk of leukemia in general, total lymphatic and hematopoietic cancers, and other specific types of leukemia, such as chronic lymphocytic leukemia (Savitz and Andrews 1997; NTP 2005). The health effects of benzene were most recently reviewed by ATSDR (2007). The central conclu- sions of that review are summarized below.

OCR for page 258
Contaminated Water Supplies at Camp Lejeune—Assessing Potential Health Effects 264 The carcinogenicity of benzene in exposed workers is well documented. Epidemiologic studies of occupational cohorts provide clear evidence of a causal relationship between occupational exposure to benzene and benzene-containing solvents and acute myelogenous leukemia. All leukemias and myelodys- plastic syndromes have been linked to occupational exposure to benzene at high concentrations, and there appears to be a dose-response relationship. Other cancer outcomes associated with occupational exposure to benzene in some studies are non-Hodgkin lymphoma and multiple myeloma; however, these associa- tions have not been consistently observed among studies. Benzene has been shown to have adverse hematologic and immunologic effects. All the major types of blood cells are susceptible (erythrocytes, leukocytes, and platelets). Severe toxicity may result in hypercellular bone marrow that exhibits ineffective hematopoiesis and pancytopenia (reduced numbers of all types of blood cells). Severe damage to the bone marrow involving cellular aplasia is known as aplas- tic anemia and can lead to leukemia. Early studies of benzene-exposed workers demonstrated that chronic exposure to benzene at air concentrations of 10 ppm or more had adverse hematologic effects, which in- creased in severity with increasing benzene concentration. More recent epidemiologic studies have ob- served hematologic effects (including significant reductions in the numbers of various types of blood cells) in workers chronically exposed to benzene at less than 10 ppm and even at 1 ppm or less. After in- halation exposure for intermediate and chronic durations, benzene has had adverse immunologic effects, including decreases in concentrations of antibodies and leukocytes in benzene-exposed workers. The current literature suggests that humans exposed to benzene in an occupational setting for acute, intermediate, or chronic durations by inhalation and orally are at risk for neurologic effects. How- ever, benzene concentrations in ambient air, in drinking water, and at hazardous-waste sites are lower and not likely to be of concern. Limited information is available on other systemic effects in humans and is associated with high exposure. Respiratory effects, dermal effects (skin irritation and burns), ocular ef- fects (irritation), and cardiovascular effects (particularly ventricular fibrillation) have been suggested after exposure to benzene vapors. Gastrointestinal effects have been noted after fatal inhalation exposure (con- gestive gastritis) or ingestion (toxic gastritis and pyloric stenosis). Reports of renal effects refer to renal congestion after fatal inhalation exposure. The evidence of effects of benzene exposure on human reproduction is not sufficient to demon- strate a causal association. Epidemiologic studies implicating benzene as a developmental toxicant have many limitations, and it is not possible to assess the effect of benzene on the human fetus. METHYLENE CHLORIDE MC is used in various industrial processes, including paint stripping, pharmaceutical manufactur- ing, paint-remover manufacturing, and metal cleaning and degreasing. It may also be found in some aerosol and pesticide products and is used in the manufacture of photographic film. MC is a toxic chemi- cal that is known to cause death in humans at high doses (ATSDR 2000a). Human fatalities are most of- ten associated with effects on the nervous system. In general, people can be exposed through air, water, food, or such products as paint thinner (ATSDR 2000a). ATSDR (2000a) reviewed the scientific literature for toxicologic profile. The Office of Environmental Health Hazard Assessment of the California Envi- ronmental Protection Agency also reviewed the available studies to develop a public-health goal for MC in drinking water (CalEPA 2000b). In addition, three organizations reviewed the scientific literature to determine whether MC causes cancer. The NTP concluded that MC is “reasonably anticipated” to be a human carcinogen on the basis of evidence of carcinogenicity in mice. In 1999, IARC concluded that MC was “possibly carcinogenic to humans.” In 1991, EPA classified it as a “probable human carcinogen” on the basis of sufficient evidence of hepatic and lung cancer and mammary tumors in experimental animals (EPA 1991). EPA announced that it had begun a reassessment of MC, but no findings have been posted. In 1992, EPA adopted a maximum contaminant level (MCL) in drinking water of 5 ppb and an MCL goal of 0 ppb, citing concerns about hepatic effects and cancer (EPA 2003). The MCLs reflected

OCR for page 258
Appendix D 265 consideration of the potential for health effects and of the feasibility and cost of treatment technologies and so may not represent health-based standards. California adopted a public-health goal in drinking wa- ter of 4 ppb on the basis solely of health concerns. The California drinking-water standard, like the federal standard, is 5 ppb and was adopted in 1994 (CalEPA 2000b). IOM (2003) reviewed the human health effects of chronic exposure to MC, including results of several occupational studies, such as those of aircraft-maintenance workers (Blair et al. 1998), cellulose- fiber production-plant workers (Lanes et al. 1993; Gibbs et al. 1996), photographic-film base- manufacturing workers (Hearne and Pifer 1999), cellulose triacetate film workers (Tomenson et al. 1997), and lamp-manufacturing workers (Shannon et al. 1988). No consistent pattern of increased risk of any health effect was found. The present committee performed an updated literature review to identify new studies since the IOM (2003) review. No new studies in which exposure to MC could be specifically evaluated were found. IOM concluded that there was inadequate/insufficient evidence to determine whether there is an association between MC and cancer or neurologic, reproductive, developmental, or other health effects. The committee supports IOM’s conclusions. We also surveyed reports published since the earlier reviews were performed. Little testing has been done for additional health end points. Most of the published research focuses on the interpretation of data from studies in animals and addresses such issues as differences between mice and humans (e.g., Jonsson and Johanson 2001; Sherratt et al. 2002; Slikker et al. 2004), development of physiologically based pharmacokinetic models (e.g., Sweeney et al. 2004), and application of findings to cancer risk as- sessment (e.g., David et al. 2006; Marino et al. 2006; Starr et al. 2006). One study reported that ingestion of acetaminophen, a commonly used analgesic, increased the activation of MC in rats (Kim et al. 2007). With regard to additional studies of end points of concern, the committee found one new investigation of the immunotoxicity of MC, which is discussed below. Hepatic Toxicity Studies of animals exposed to MC in drinking water have reported effects on the liver. Kirschman et al. (1986) reported changes in hepatic cells (including centrilobular necrosis, granulomatous foci, and cytoplasmic eosinophilic bodies) in male rats after 90 days of exposure to MC in drinking water at 1,200 mg/kg per day. Less serious effects were observed at the lowest dose, 166 mg/kg per day, in males and a slightly higher dose in females. MC was reported to alter the distribution of lipids among tissues. The study also reported changes in blood chemistry characteristics, such as fasting glucose, cholesterol, and triglyceride values, at all doses, at 1 and 3 mo. The same authors reported subtle centrilobular fatty changes in male B6C3F1 mice exposed for 90 days at 587 mg/kg per day. Serota et al. (1986a,b) reported hepatic changes, including cellular alterations in Fischer rats ex- posed to MC for 78-104 weeks at 55 mg/kg per day and increased hepatic fat in B6C3F1 mice exposed for 2 years at 236 mg/kg per day. EPA reported a NOAEL of 5.8 and 6.5 mg/kg per day for histologic alterations of the liver in male and female rats, respectively, exposed during a 2-year bioassay of exposure in drinking water (EPA 1988). The lowest observed-adverse-effects levels (LOAELs) reported were 52.6 and 58 mg/kg per day in male and female rats, respectively (National Coffee Association [1982], as cited by EPA 1988). EPA used those values to set a reference dose for exposure in drinking water of 0.06 mg/kg per day. EPA has not set a reference dose for inhalation exposure. Kjellstrand et al. (1986) reported increased hepatic weight in mice exposed at 75 ppm for 90 days. No NOAEL was reported. Burek et al. (1984) reported hepatocellular vacuolization and multinucleated hepatocytes in Sprague-Dawley rats after exposure at 500 ppm for 2 years 5 days/week and 6 h/day but did not report a NOAEL. Nitschke et al. (1988a,b) reported multinucleated hepatocytes in females of the same species after inhalation exposure at 200 ppm for the same duration, with a NOAEL of 50 ppm. Those data were used by ATSDR to derive a chronic inhalation minimal risk level of 0.3 ppm. In 2-year MC bioassays with rats, hepatocellular vacuolization and multinucleate hepatocytes were found at a con-

OCR for page 258
Contaminated Water Supplies at Camp Lejeune—Assessing Potential Health Effects 266 centration of 500 ppm (NTP 1986d; Nitschke et al. 1988a). NTP (1986d) also reported hepatic he- mosiderosis, cytomegaly, necrosis, granulomatous inflammation, and bile duct fibrosis. Reproductive Toxicity The NTP (1986d) exposed mice and rats to MC by inhalation at up to 1,500 ppm for 2 years. Mice exhibited atrophy of the uterus, ovary, and testes. In a dominant lethal study, no microscopic effects on the testes were found in mice exposed to MC at vapor concentrations up to 200 ppm (Raje et al. 1988). In a two-generation reproductive-toxicity study, no effects on fertility, litter size, neonatal growth, or sur- vival were found in rats exposed by inhalation at up to 1,500 ppm (Nitschke et al. 1988a). Developmental Toxicity Schwetz et al. (1975) reported an extra ossification in the sternum or delayed ossification of sternebrae in rats and mice exposed to MC by inhalation at 1,250 ppm. An increased incidence of dilated renal pelvis was also observed in rats. In another study, no teratogenic effects were reported after rats were exposed at 4,500 ppm before mating or during gestation (Hardin and Manson 1980), but a followup study of the offspring found alterations in rates of behavioral habituation to novel environments. Several other studies of exposure to MC during reproduction or development found no significant effects on sur- vival, viability, growth, or development (ATSDR 2000a). Neurotoxicity Two studies reported neurologic effects. Briving et al. (1986b) reported alterations in the amino acids present in the brain in gerbils exposed by inhalation at 210 ppm for 3 mo. Rosengren et al. (1986b) reported decreased DNA concentrations in the hippocampus in Mongolian gerbils exposed by inhalation at 210 ppm for 7-16 weeks. Negative findings in some neurologic tests in rats after exposure at 2,000 ppm for 13 weeks have been reported (Mattsson et al. 1990). Immunotoxicity One study has looked at immune system effects. Warbrick et al. (2003) exposed Sprague-Dawley rats to MC by inhalation at 5,000 ppm by inhalation for 6 h/day 5 days/week for 28 days. Immune re- sponse was evaluated by the capacity of the rats to mount an antibody response to sheep red blood cells. The study reported that relative spleen weight was reduced in females but not in males. The authors re- ported no significant differences in antibody production between treated rats and controls. Hematologic Effects MC can contribute to an increase in concentrations of carbon monoxide in the blood, as first documented in a 1993 case report (ATSDR 2000a). That can cause hypoxia. Recent results suggest that the effect can be enhanced by coexposure to acetaminophen, a widely used medication (Kim et al. 2007). The significance of the report for chronic exposure does not appear to have been assessed. Similar effects may be of concern in connection with other solvents that are metabolized through pathways similar to that of MC, including others included in this report. The issue may warrant additional attention.

OCR for page 258
Appendix D 267 Genotoxicity Mixed results have been found in genotoxicity assays of MC. In vitro studies with human cells have reported that MC induced sister-chromatid exchanges, chromosomal breaks, and chromosomal loss, but studies with rodent cells have not. Single-strand breaks in DNA have been observed in studies with mammalian cells, but there has been no evidence of mutations (IARC 1999b). There is some evidence of tissue-specific genotoxic effects (Sasaki et al. 1998), which could be related to the differential expression of metabolizing enzymes. Cancer Three studies reported cancer in experimental animals after inhalation exposure. Mennear et al. (1988) exposed Fischer 344 rats to MC at 1,000-4,000 ppm 6 h/day 5 days/week for 102 weeks and re- ported an increase in mammary tumors in males at 4,000 ppm and in females at all doses. The NTP (1986d) reported the same results. That strain of rat is known to have a high background incidence of tu- mors. Nitschke et al. (1988b) exposed rats at lower doses (0, 50, 200, and 500 ppm) in another 2-year study and reported increases in numbers of tumors per animal in females in the 500-ppm group; no effects were reported in males. Mennear et al. (1988) exposed B6C3F1 mice to MC at 2,000 or 4,000 ppm 6 h/day 5 days/week for 102 weeks and reported increases in hepatic and lung tumors in mice exposed at 2,000 ppm or higher. The NTP (1986d) reported the same result. Maltoni et al. (1988b) reported a statistically significant increase in pulmonary tumors in male mice treated with MC by gavage at 500 mg/kg per day for 64 weeks. Supporting evidence of lung-tumor development in mice after inhalation exposure to MC is found in studies by Kari et al. (1993) and Maron- pot et al. (1995). A 2-year drinking-water study with MC up to 250 mg/kg per day found an increase in the inci- dence of combined hepatocellular carcinomas and neoplastic nodules in female rats and male mice com- pared with concurrent controls (Serota et al. 1986a,b). However, the incidence was within the range for historical controls, and there was no dose-response relationship. Other Effects Other effects of MC reported in experimental animal studies include alterations in urinary pH and renal weights in rats and renal tubular changes in dogs, rats, and mice after inhalation exposure (ATSDR 2000a; CalEPA 2000b). TOLUENE The health effects of toluene have recently been reviewed by ATSDR (2000b). This section will first summarize the central conclusions of the ATSDR review pertaining to human studies and then sum- marize the toxicologic evidence. The existing information on human health effects comes from studies of acute, intermediate, and chronic exposure primarily by inhalation. The nervous system appears to be par- ticularly susceptible to the effects of toluene. Effects range from reversible acute effects (fatigue, head- aches, decrease in manual dexterity, and narcosis) to persistent neurologic impairment in people who abused solvents or inhaled toluene at high concentrations. Subtle alterations in neurologic functions (cog- nitive functions, hearing, and color discrimination) have been found in workers chronically exposed at lower concentrations.

OCR for page 258
Contaminated Water Supplies at Camp Lejeune—Assessing Potential Health Effects 268 Animal and human evidence—alterations in concentrations of hormones (follicle-stimulating hormone, leutenizing hormone, and testosterone) and decreased sperm counts—suggests that toluene may have endocrine-disrupting effects in males and females. However, there are few epidemiologic studies of adverse reproductive effects in humans. Finnish studies of occupational toluene exposure of women or of wives of occupationally exposed men suggested an increased risk of miscarriage, but the studies had a number of limitations. There have been a series of case reports of birth defects in the offspring of women who intentionally inhaled large amounts of toluene or organic solvents during pregnancy. One small Fin- nish study reported that the opffspring of women occupationally exposed to a mixture of solvents had in- creases in CNS anomalies. The ATSDR review included 11 epidemiologic studies of toluene and cancer risk. In general, toluene was not associated with an increased risk of cancer at most sites. Three cohort studies included workers exposed to toluene. They suggested an association with several cancers—including lung cancer, gastric cancer, and colon cancer—but consistent patterns of association with measures of cumulative ex- posure were not found. Those and other studies also could not rule out confounding by other chemicals, such as benzene. With regard to other health effects, case reports of solvent abusers have shown some association with cardiac arrhythmia. Other health effects—hematologic, hepatic, or renal—have not been consistently reported. The toxicology, pharmacokinetics, epidemiology, and health risks associated with exposure have been well documented (EPA 1983a,b, 1990; IARC 1988, 1989; ATSDR 2000b; ACGIH 2007). Chronic exposure to toluene at 50-200 ppm in air can produce neurobehavioral impairments, including impair- ments in cognitive and neuromuscular performance, hearing, and color discrimination. At higher concen- trations, exposure can produce CNS effects, including encephalopathy, headache, fatigue, impairment in coordination, transient memory loss, and impairment in reaction time. Evidence of those effects is found in reports of controlled animal experiments (Dyer et al. 1988; NTP 1990b; von Euler et al. 1993, 2000; Mehta et al. 1998; ATSDR 2000b) and in the epidemiologic literature, especially reports of occupational studies of toluene (Iregren 1982; Orbaek and Nise 1989; Vrca et al. 1997a,b; Cavalleri et al. 2000; Cam- pagna et al. 2001; ACGIH 2007). Results of dosimetric studies of acute behavioral effects of toluene in rats have been used for quantitative comparison of the effects in humans (Benignus et al. 2007; Boyes et al. 2007; Bushnell et al. 2007). There is agreement in the scientific community that toluene is not carcino- genic at lifetime exposures up to 1,200 ppm (NTP 1990b; ATSDR 2000b; Huff 2003). Toluene has had negative results for mutagenicity in a number of test systems (Nestmann et al. 1980; McCarroll et al. 1981). Results of animal studies indicate that toluene is not a teratogenic agent but can retard fetal growth, skeletal development, and behavior of offspring at 1,500 ppm, at which maternal weight gain is also affected (Saillenfait et al. 2007). Another recent study of developmental and reproductive toxicity in rats indicated a NOAEL for maternal toxicity of 750 ppm and a LOAEL of 1,500 ppm for maternal and developmental toxicity (Roberts et al. 2007). In summary, chronic inhalation exposure to toluene at 50-200 ppm can produce neurobehavioral impairment. Both maternal toxicity and developmental toxicity are observed at the relatively high expo- sure concentration of 1,500 ppm. Information from well-conducted studies indicates that toluene is not carcinogenic or mutagenic. VINYL CHLORIDE The health effects of VC have recently been reviewed by ATSDR (2006). VC is produced primar- ily (98% of total production) for use in the manufacture of polyvinyl chloride (PVC). PVC materials are used in a variety of products, including automotive parts, packaging products, pipes, and construction ma- terial. The primary route of exposure to VC is through ambient air around VC production facilities. It can also be present in groundwater or drinking water because of microbial degradation of other chlorinated

OCR for page 258
Appendix D 269 solvents. However, its rapid volatilization decreases the probability of such exposure of the general popu- lation. The liver appears to be particularly susceptible to the effects of exposure to VC by inhalation. Hepatic damage—such as hepatomegaly, hyperplasia and hypertrophy of hepatocytes and sinusoidal cells, and cirrhosis (independent of alchohol consumption—has been observed. The association between VC and angiosarcoma of the liver (a very rare cancer in humans) has been demonstrated in numerous oc- cupational and animal studies. Other cancer outcomes associated with VC exposure in some studies in- clude hepatocellular carcinoma, cholangiocellular carcinoma, and cancers of the lung and respiratory tract, the lymphatic-hematopoietic system, and the CNS. However, those associations have not been con- sistent among studies. VC has been classified as “carcinogenic to humans” by IARC (1979, 1987), a “known human carcinogen by the inhalation route of exposure” by EPA (2000), and “known to be a hu- man carcinogen” by the NTP (2005) on the basis of the findings of epidemiologic and animal studies. The key animal data and findings from those reviews are discussed briefly below and are updated with studies published since the reviews were performed. Additional outcomes have been assessed in epidemiologic studies of workers exposed to VC. Re- versible CNS effects—such as dizziness, drowsiness, and headache—have been reported after acute inha- lation of high concentrations of VC. Peripheral neuropathy has been reported in workers. Adverse respira- tory effects have been observed in some studies but not others. Many of the studies may be confounded by smoking and exposure to PVC resin dust. Development of Raynaud phenomenon (a condition in which the fingers blanch and become numb with discomfort on exposure to cold) has been associated with current occupational exposure. A condition labeled vinyl chloride disease—consisting of Raynaud phenomenon, acroosteolysis, joint and muscle pain, enhanced collagen deposition, stiffness of the hands, and scleroderma-like skin changes—has been identified in some VC workers. In some cases, there has been a correlation with immunologic abnormalities. Occupational exposure to VC has also been impli- cated in alterations in the immune system, including increased percentages of lymphocytes and increased circulating immune complexes (for example, cryoglobulinemia). There is evidence of increased risk of hypertension associated with VC exposurebut no conclusive evidence of an association with coronary heart disease. Reproductive and developmental effects have also been observed. Case studies have reported sexual impotence and loss of libido in male workers. An increase in pre-eclampsia has been observed. Studies have reported an excess of fetal loss in wives of men exposed to VC. Increases in birth defects— including clubfoot and malformations of the CNS, upper alimentary tract, and genital organs—have been reported in populations exposed to emissions from PVC polymerization facilities. VC is considered a known human carcinogen mainly on the basis of the consistent observation of excess rates of angiosarcoma of the liver in workers exposed via inhalation. According to the review by ATSDR, there is limited/suggestive evidence of associations between VC and Raynaud phenomenon, scleroderma-like skin changes, and other immunologic effects. There is inadequate/insufficient evidence to support a conclusion about associations between chronic exposure to VC and reproductive and developmental effects. Specific health effects of VC in animals is discussed be- low. Hepatic Toxicity Hepatic lesions were found in rats exposed chronically to VC in their feed (1.3 mg/kg per day) (Feron et al. 1981; Til et al. 1991). The nonneoplastic lesions included hepatic-cell polymorphism and hepatic cysts. When exposed by inhalation, rats have developed hepatocellular degeneration, hepatic swelling with compression of sinusoids, altered enzyme activity, proliferation of reticulocytes, and in- creased ratio of liver weight to bodyweight (EPA 2000; ATSDR 2006). Hepatic toxicity is thought to be due to the reactive metabolites of VC that bind to hepatic proteins, DNA, and RNA (ATSDR 2006).

OCR for page 258
Contaminated Water Supplies at Camp Lejeune—Assessing Potential Health Effects 270 Renal Toxicity At high concentrations (300,000 ppm), VC caused renal congestion and degenerative changes. At lower concentrations (3,000 ppm) for longer durations, VC has been reported to increase ratios of renal weight to bodyweight, but this was an inconsistent finding (ATSDR 2006). Pulmonary Toxicity At high concentrations, VC is irritating to the respiratory tracts of experimental animals (ATSDR 2006). Chronic-exposure studies have reported a slightly higher incidence of hyperplasia of the olfactory epithelium, increased cellularity of the interalveolar septa, and pulmonary hemorrhage in rats exposed at 5,000 ppm (Feron and Kroes 1979). Reproductive Toxicity Some inhalation studies of VC have found effects on male reproduction in rats, including damage to the seminiferous tubules and spermatogenic epithelium, depletion of spermatocytes, disorders of sper- matogenesis, and decreases in the ratio of pregnant to mated females at concentrations as low as 100 ppm (Sokal et al. 1980; Bi et al. 1985). Other studies, including a two-generation toxicity study of rats exposed to VC at up to 1,100 ppm (Thornton et al. 2002), did not find such effects. Questions have been raised about the methodology of some studies that reported positive effects (ATSDR 2006). EPA (2000) identi- fied the no-observed-adverse-effect level (NOAEL) for reproductive effects as over 1,100 ppm. Developmental Toxicity John et al. (1977, 1981) evaluated the effects of VC on the embryonal and fetal development of mice, rats, and rabbits. Developmental effects were found in mice after in utero exposure to VC. At an inhalation concentration of 500 ppm, the effects included increased fetotoxicity and fetal resorptions, de- creased fetal bodyweight, smaller litters, and retarded cranial and sternal ossification. In rats exposed at higher concentrations, an increased incidence of dilated ureters was found in offspring. In both mice and rats, the effects on offspring were observed at concentrations that produced maternal toxicity, as evi- denced by increased mortality, reduced bodyweight, and reduced absolute hepatic weight in the dams. No effects were found in rabbits. No embryo-fetal developmental toxicity was found in a two-generation reproductive-toxicity study of rats exposed to VC at inhalation concentrations up to 1,100 ppm (Thornton et al. 2002). Neurotoxicity Like other solvents, VC at high concentrations had neurotoxic effects, such as ataxia, uncon- sciousness, incoordination, and tremors. After chronic exposure by inhalation (30,000 ppm), rats had de- creased responses to external stimuli, surrounding and infiltration of peripheral nerve ends with fibrous tissue, and brain lesions (CalEPA 2000a; ATSDR 2006). Immunotoxicity A few studies have reported that VC has an immune-stimulating effect on mice and causes splenomegaly in them (ATSDR 2006). Stimulation of spontaneous lymphocyte transformation was ob-

OCR for page 258
Appendix D 271 served after 2 weeks of exposure at 1,000 ppm and then after 4-8 weeks of exposure at concentrations as low as 10 ppm (Sharma and Gehring 1979). Genotoxicity VC is a well-established genotoxicant, having been investigated in a variety of test systems, in- cluding in vitro studies of bacteria, fungi, and mammalian cells and in vitro studies of rodents and humans (ATSDR 2006). It has been shown to be mutagenic, and its mutagenicity is enhanced with metabolic acti- vation; this suggests that one of its metabolites is more mutagenic than VC (CalEPA 2000a; ATSDR 2006). Cancer VC has been shown to cause cancer in multiple organs and multiple species when inhaled or in- gested (IARC 1979; EPA 2000; ATSDR 2006). The association between VC and hepatic angiosarcomas in the epidemiologic literature is supported by similar findings in mice (e.g., Drew et al. 1983), rats (e.g., Feron et al. 1981; Maltoni et al. 1981; Drew et al. 1983; Bi et al. 1985), and hamsters (e.g., Drew et al. 1983). Tumors in rats were found after oral exposure at concentrations as low as 1.7 mg/kg per day. Other cancers found in rats were Zymbal-gland tumors, mammary-gland tumors, neuroblastomas, and lung tumors (Feron et al. 1981; Maltoni et al. 1981; Drew et al. 1983; Til et al. 1991). Mice exposed by inhalation developed lung tumors, mammary-gland tumors, and angiosarcomas and adenocarcinomas in various sites (Drew et al. 1983). Hamsters also developed hemangiosarcomas, mammary-gland carci- nomas, gastric adenocarcinomas, and skin carcinomas (Drew et al. 1983). Some studies have shown that younger rats are more susceptible to the carcinogenicity of VC (Drew et al. 1983; Maltoni and Cotti 1988).