An Analysis of Contaminated Well Water and Health Effects in Woburn, Massachusetts

The Battle of Battle Creek: Seeking Superfund Justice

An early epidemiologic study on groundwater contamination in the United States took place at an Environmental Protection Agency (EPA) Superfund site in Battle Creek Michigan. Volatile organic compounds (VOCs) consisting of chlorinated 2-carbon solvents were identified in private and municipal wells serving several communities. One major source of VOC was a solvent recovery operation near the municipal well field. The study modeled the VOC plume and investigated mortality and morbidity outcomes thought to be related to the VOC. Although quite statistically significant excess mortality and morbidity (hospital discharge and survey questionnaire) outcomes were observed, there were few associations with VOC water cumulative metrics. Another potentially dominant class of exposures could arise in VOC water contamination episodes from the diverse contents of spent solvents generated in multiple, local manufacturing activities. The findings at Battle Creek are re-interpreted in this light and the implications for Superfund-like investigation strategy and reporting are discussed.

Toxicity assessments of selected trichloroethylene and perchloroethylene metabolites in three in vitro human placental models

Residential and occupational exposures to the industrial solvents perchloroethylene (PERC) and trichloroethylene (TCE) present public health concerns. In humans, maternal PERC and TCE exposures can be associated with adverse birth outcomes. Because PERC and TCE are biotransformed to toxic metabolites and placental dysfunction can contribute to adverse birth outcomes, the present study compared the toxicity of key PERC and TCE metabolites in three in vitro human placenta models. We measured cell viability and caspase 3 + 7 activity in the HTR-8/SVneo and BeWo cell lines, and caspase 3 + 7 activity in first trimester villous explant cultures. Cultures were exposed for 24 h to 5-100 µM S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC), or 5-200 µM trichloroacetate (TCA) and dichloroacetate (DCA). DCVC significantly reduced cell viability and increased caspase 3 + 7 activity in HTR-8/SVneo cells at a lower concentration (20 µM) compared with concentrations toxic to BeWo cells and villous explants. Similarly, TCVC reduced cell viability and increased caspase 3 + 7 activity in HTR-8/SVneo cells but not in BeWo cells. TCA and DCA had only negligible effects on HTR-8/SVneo or BeWo cells. This study advances understanding of potential risks of PERC and TCE exposure during pregnancy by identifying metabolites toxic in placental cells and tissues.

Why We Will Continue to Lose Our Battle with Cancers If We Do Not Stop Their Triggers from Environmental Pollution

Besides our current health concerns due to COVID-19, cancer is a longer-lasting and even more dramatic pandemic that affects almost a third of the human population worldwide. Most of the emphasis on its causes has been posed on genetic predisposition, chance, and wrong lifestyles (mainly, obesity and smoking). Moreover, our medical weapons against cancers have not improved too much during the last century, although research is in progress. Once diagnosed with a malignant tumour, we still rely on surgery, radiotherapy, and chemotherapy. The main problem is that we have focused on fighting a difficult battle instead of preventing it by controlling its triggers. Quite the opposite, our knowledge of the links between environmental pollution and cancer has surged from the 1980s. Carcinogens in water, air, and soil have continued to accumulate disproportionally and grow in number and dose, bringing us to today's carnage. Here, a synthesis and critical review of the state of the knowledge of the links between cancer and environmental pollution in the three environmental compartments is provided, research gaps are briefly discussed, and some future directions are indicated. New evidence suggests that it is relevant to take into account not only the dose but also the time when we are exposed to carcinogens. The review ends by stressing that more dedication should be put into studying the environmental causes of cancers to prevent and avoid curing them, that the precautionary approach towards environmental pollutants must be much more reactionary, and that there is an urgent need to leave behind the outdated petrochemical-based industry and goods production.

Placenta as a target of trichloroethylene toxicity

Trichloroethylene (TCE) is an industrial solvent and a common environmental contaminant detected in thousands of hazardous waste sites. Risk of exposure is a concern for workers in occupations that use TCE as well as for residents who live near industries that use TCE or who live near TCE-contaminated sites. Although renal, hepatic and carcinogenic effects of TCE have been documented, less is known about TCE impacts on reproductive functions despite epidemiology reports associating maternal TCE exposure with adverse pregnancy outcomes. Toxicological evidence suggests that the placenta mediates at least some of the adverse pregnancy outcomes associated with TCE exposure. Toxicology studies show that the TCE metabolite, S-(1,2-dichlorovinyl)-l-cysteine (DCVC) generates toxic effects such as mitochondrial dysfunction, apoptosis, oxidative stress, and release of prostaglandins and pro-inflammatory cytokines in placental cell lines. Each of these mechanisms of toxicity have significant implications for placental functions and, thus, ultimately the health of mother and developing child. Despite these findings there remain significant gaps in our knowledge about effects of TCE on the placenta, including effects on specific placental cell types and functions as well as sex differences in response to TCE exposure. Due to the critical role that the placenta plays in pregnancy, future research addressing some of these knowledge gaps could lead to significant gains in public health.

Exposure to Trichloroethylene Metabolite S-(1,2-Dichlorovinyl)-L-cysteine Causes Compensatory Changes to Macronutrient Utilization and Energy Metabolism in Placental HTR-8/SVneo Cells

Trichloroethylene (TCE) is a widespread environmental contaminant following decades of use as an industrial solvent, improper disposal, and remediation challenges. Consequently, TCE exposure continues to constitute a risk to human health. Despite epidemiological evidence associating exposure with adverse birth outcomes, the effects of TCE and its metabolite S-(1, 2-dichlorovinyl)-L-cysteine (DCVC) on the placenta remain undetermined. Flexible and efficient macronutrient and energy metabolism pathway utilization is essential for placental cell physiological adaptability. Because DCVC is known to compromise cellular energy status and disrupt energy metabolism in renal proximal tubular cells, this study investigated the effects of DCVC on cellular energy status and energy metabolism pathways in placental cells. Human extravillous trophoblast cells, HTR-8/SVneo, were exposed to 5–20 μM DCVC for 6 or 12 h. After establishing concentration and exposure duration thresholds for DCVC-induced cytotoxicity, targeted metabolomics was used to evaluate overall energy status and metabolite concentrations from energy metabolism pathways. The data revealed glucose metabolism perturbations including a time-dependent accumulation of glucose-6-phosphate+frutose-6-phosphate (G6P+F6P) as well as independent shunting of glucose intermediates that diminished with time, with modest energy status decline but in the absence of significant changes in ATP concentrations. Furthermore, metabolic profiling suggested that DCVC stimulated compensatory utilization of glycerol, lipid, and amino acid metabolism to provide intermediate substrates entering downstream in the glycolytic pathway or the tricarboxylic acid cycle. Lastly, amino acid deprivation increased susceptibility to DCVC-induced cytotoxicity. Taken together, these results suggest that DCVC caused metabolic perturbations necessitating adaptations in macronutrient and energy metabolism pathway utilization to maintain adequate ATP levels.

The trichloroethylene metabolite S-(1,2-dichlorovinyl)-L-cysteine induces progressive mitochondrial dysfunction in HTR-8/SVneo trophoblasts

Trichloroethylene is an industrial solvent and common environmental pollutant. Despite efforts to ban trichloroethylene, its availability and usage persist globally, constituting a hazard to human health. Recent studies reported associations between maternal trichloroethylene exposure and increased risk for low birth weight. Despite these associations, the toxicological mechanism underlying trichloroethylene adverse effects on pregnancy remains largely unknown. The trichloroethylene metabolite S-(1,2-dichlorovinyl)-L-cysteine (DCVC) induces mitochondrial-mediated apoptosis in a trophoblast cell line. To gain further understanding of mitochondrial-mediated DCVC placental toxicity, this study investigated the effects of DCVC exposure on mitochondrial function using non-cytolethal concentrations in placental cells. Human trophoblasts, HTR-8/SVneo, were exposed in vitro to a maximum of 20 μM DCVC for up to 12 h. Cell-based oxygen consumption and extracellular acidification assays were used to evaluate key aspects of mitochondrial function. Following 6 h of exposure to 20 μM DCVC, elevated oxygen consumption, mitochondrial proton leak and sustained energy coupling deficiency were observed. Similarly, 12 h of exposure to 20 μM DCVC decreased mitochondrial-dependent basal, ATP-linked and maximum oxygen consumption rates. Using the fluorochrome TMRE, dissipation of mitochondrial membrane potential was detected after a 12-h exposure to 20 μM DCVC, and (±)-α-tocopherol, a known suppressor of lipid peroxidation, attenuated DCVC-stimulated mitochondrial membrane depolarization but failed to rescue oxygen consumption perturbations. Together, these results suggest that DCVC caused progressive mitochondrial dysfunction, resulting in lipid peroxidation-associated mitochondrial membrane depolarization. Our findings contribute to the biological plausibility of DCVC-induced placental impairment and provide new insights into the role of the mitochondria in DCVC-induced toxicity.

Modeled exposure to tetrachloroethylene-contaminated drinking water and the occurrence of birth defects: a case-control study from Massachusetts and Rhode Island

BACKGROUND

Residents of Massachusetts and Rhode Island were exposed to tetrachloroethylene-contaminated drinking water from 1968 through the early 1990s when it leached from the vinyl lining of asbestos cement water distribution pipes. While occupational exposure to solvents during pregnancy has consistently been linked to an increased risk of certain birth defects, mixed results have been observed for environmental sources of exposure, including contaminated drinking water. The present case-control study was undertaken to examine further the association between prenatal exposure to tetrachloroethylene-contaminated drinking water and the risk of central nervous system defects, oral clefts and hypospadias.

METHODS

Cases were comprised of live- and stillborn infants delivered between 1968 and 1995 to mothers who resided in 28 Massachusetts and Rhode Island cities and towns with some PCE-contaminated water supplies. Infants with central nervous system defects (N = 268), oral clefts (N = 112) and hypospadias (N = 94) were included. Controls were randomly selected live-born, non-malformed infants who were delivered during the same period and geographic area as cases (N = 771). Vital records and self-administered questionnaires were used to gather identifying information, birth defect diagnoses, and other relevant data. PCE exposure during the first trimester was estimated using water distribution system modeling software that incorporated a leaching and transport model. Prenatal PCE exposure was dichotomized as "high" or "low" exposure at the level corresponding to an estimated average concentration of 40 μg/L, the criterion for remediation when PCE contamination was discovered in 1980.

RESULTS

Mothers with "high" levels of exposure to PCE-contaminated drinking water during the first trimester (> 40 μg/L) had increased odds of having a child with spina bifida (OR: 2.0, 95% CI: 0.8-5.4), cleft lip with or without cleft palate (OR: 3.8, 95% CI: 1.2-12.3) and hypospadias (OR: 2.1, 95% CI:0.5-8.3). No increases in the odds of other defects were observed in relation to "high" exposure levels.

CONCLUSIONS

The results of the present study suggest that mothers with "high" PCE exposure levels during the first trimester have increased odds of having a child with spina bifida, cleft lip with or without cleft palate, and hypospadias. These findings support several prior studies that observed an increased risk of selected birth defects following prenatal exposure to solvents in occupational and environmental settings. Even though PCE contamination from vinyl lined pipes was remediated many years ago, it remains a widespread contaminant across the U.S and so environmental regulations must be guided by a precautionary perspective that safeguards pregnant women and their offspring.

Exposure to tetrachloroethylene-contaminated drinking water and time to pregnancy

BACKGROUND

The synthetic solvent tetrachloroethylene (PCE), commonly used in dry cleaning operations, is a human neurotoxicant and carcinogen. However, its effect on reproduction is poorly understood, as prior studies have been limited to small occupational cohorts. We examined the association between PCE exposure from contamination of the public drinking water supply and time-to-pregnancy (TTP) in a cohort of mothers from Cape Cod, Massachusetts.

METHODS

The Cape Cod Family Health Study is a retrospective cohort study designed to examine the reproductive and developmental health effects of exposure to PCE-contaminated drinking water. Our analysis included 1565 women who reported 3826 planned pregnancies from 1949 to 1990. Women completed self-administered questionnaires that ascertained TTP for each of her pregnancies, regardless of the outcome, as well as residential history and demographic information. We utilized EPANET water distribution system modeling software and a leaching and transport model to assess PCE exposure for each pregnancy. We used log-binomial regression models to estimate relative risks (RR) and 95% confidence intervals (CI), adjusting for potential confounders. We performed a probabilistic bias analysis to examine the effect of outcome misclassification on our results.

RESULTS

Any cumulative PCE exposure before pregnancy was associated with a 15% reduction in risk of TTP > 12 months (RR = 0.85, 95% CI: 0.70, 1.03). However, women with the highest average monthly PCE exposure around the time of the pregnancy attempt (≥ 2.5 g) had increased risk of TTP > 12 months (RR = 1.36, 95% CI: 1.06, 1.76).

CONCLUSIONS

We found little evidence for long-term, cumulative adverse effects of PCE exposure on TTP, but high levels of PCE exposure around the time of the pregnancy attempt were associated with longer TTP. These associations may be underestimated due to the exclusion of unsuccessful pregnancy attempts from our study population, and may be biased by outcome and exposure misclassification given the long-term recall of TTP and use of a leaching and transport model to estimate PCE exposure.

Modeled exposure to tetrachloroethylene-contaminated drinking water and the risk of placenta-related stillbirths: a case-control study from Massachusetts and Rhode Island

BACKGROUND

Residents of Massachusetts and Rhode Island were exposed to tetrachloroethylene (PCE)-contaminated drinking water from 1968 through the early 1990s when the solvent was used to apply a vinyl liner to drinking water mains to address taste and odor problems. Few studies have examined the risk of fetal death among women exposed to solvent-contaminated drinking water. Two previous investigations found moderate increases in the risk of stillbirth among highly exposed women; however, these results were based on a small number of cases. The present case-control study was undertaken to examine further this association with a large number of stillbirths.

METHODS

Cases were comprised of stillborn infants delivered between 1968 and 1995 to mothers who resided in 28 Massachusetts and Rhode Island cities and towns with some affected water mains (N = 296). Cases were included if the cause of death was placental abruption and/or placental insufficiency. Controls were randomly selected live-born infants who were delivered in the same time period and geographic area (N = 783). Data on confounding variables were gathered from vital records and questionnaires. PCE exposure was estimated using a leaching and transport model integrated into water system software.

RESULTS

Mothers with any PCE exposure had a 1.7-fold increase in the adjusted odds of placenta-related stillbirth (95% CI: 1.2-2.4). The adjusted odds ratio (OR) increased as a woman's exposure level increased: in comparison to unexposed mothers, ORs were 1.5 (95% CI: 1.0-2.3) for low exposure (> 0-median), 1.7 (95% CI: 1.1-2.5) for moderate exposure (>median-90th percentile) and 1.9 (95% CI: 1.1-3.2) for high exposure (>90th percentile) (p value for trend = 0.02). A similar pattern was observed when PCE exposure was dichotomized at 40 μg/L, the suggested action guideline for remediation (OR = 1.5, 95% CI: 1.1-2.2 and OR = 2.6, 95% CI: 1.4-4.8, respectively, for PCE exposure <=40 μg/L and > 40 μg/L) (p value for trend = .003).

CONCLUSIONS

We observed a linear dose-dependent increase in the odds of stillbirth due to placental abruption and placental insufficiency with prenatal exposure to PCE contaminated drinking water. Because PCE remains a common drinking water contaminant, these findings highlight the importance of considering pregnant women when monitoring, regulating and remediating drinking water supplies.

Role of Risk of Bias in Systematic Review for Chemical Risk Assessment: A Case Study in Understanding the Relationship Between Congenital Heart Defects and Exposures to Trichloroethylene

The National Academy of Science has recommended that a risk of bias (RoB; credibility of the link between exposure and outcome) assessment be conducted on studies that are used as primary data sources for hazard identification and dose-response assessment. Few applications of such have been conducted. Using trichloroethylene and congenital heart defects (CHDs) as a case study, we explore the role of RoB in chemical risk assessment using the National Toxicology Program's Office of Health Assessment and Translation RoB tool. Selected questions were tailored to evaluation of CHD and then applied to 12 experimental animal studies and 9 epidemiological studies. Results demonstrated that the inconsistent findings of a single animal study were likely explained by the limitations in study design assessed via RoB (eg, lack of concurrent controls, unvalidated method for assessing outcome, unreliable statistical methods, etc). Such limitations considered in the context of the body of evidence render the study not sufficiently reliable for the development of toxicity reference values. The case study highlights the utility of RoB as part of a robust risk assessment process and specifically demonstrates the role RoB can play in objectively selecting candidate data sets to develop toxicity values.

Trichloroethylene metabolite S-(1,2-dichlorovinyl)-l-cysteine induces lipid peroxidation-associated apoptosis via the intrinsic and extrinsic apoptosis pathways in a first-trimester placental cell line

Trichloroethylene (TCE), a prevalent environmental contaminant, is a potent renal and hepatic toxicant through metabolites such as S-(1, 2-dichlorovinyl)-l-cysteine (DCVC). However, effects of TCE on other target organs such as the placenta have been minimally explored. Because elevated apoptosis and lipid peroxidation in placenta have been observed in pregnancy morbidities involving poor placentation, we evaluated the effects of DCVC exposure on apoptosis and lipid peroxidation in a human extravillous trophoblast cell line, HTR-8/SVneo. We exposed the cells in vitro to 10-100μM DCVC for various time points up to 24h. Following exposure, we measured apoptosis using flow cytometry, caspase activity using luminescence assays, gene expression using qRT-PCR, and lipid peroxidation using a malondialdehyde quantification assay. DCVC significantly increased apoptosis in time- and concentration-dependent manners (p<0.05). DCVC also significantly stimulated caspase 3, 7, 8 and 9 activities after 12h (p<0.05), suggesting that DCVC stimulates the activation of both the intrinsic and extrinsic apoptotic signaling pathways simultaneously. Pre-treatment with the tBID inhibitor Bl-6C9 partially reduced DCVC-stimulated caspase 3 and 7 activity, signifying crosstalk between the two pathways. Additionally, DCVC treatment increased lipid peroxidation in a concentration-dependent manner. Co-treatment with the antioxidant peroxyl radical scavenger (±)-α-tocopherol attenuated caspase 3 and 7 activity, suggesting that lipid peroxidation mediates DCVC-induced apoptosis in extravillous trophoblasts. Our findings suggest that DCVC-induced apoptosis and lipid peroxidation in extravillous trophoblasts could contribute to poor placentation if similar effects occur in vivo in response to TCE exposure, indicating that further studies into this mechanism are warranted.

Effect of sudden addition of PCE and bioreactor coupling to ZVI filters on performance of fluidized bed bioreactors operated in simultaneous electron acceptor modes

The present work evaluated the effects of (i) feeding a water contaminated with 80 mg/L PCE to bioreactors seeded with inoculum not acclimated to PCE, (ii) coupling ZVI side filters to bioreactors, and (iii) working in different biological regimes, i.e., simultaneous methanogenic aeration and simultaneous methanogenic-denitrifying regimes, on fluidized bed bioreactor performance. Simultaneous electron acceptors refer to the simultaneous presence of two compounds operating as final electron acceptors in the biological respiratory chain (e.g., use of either O₂ or NO₃^- in combination with a methanogenic environment) in a bioreactor or environmental niche. Four lab-scale, mesophilic, fluidized bed bioreactors (bioreactors) were implemented. Two bioreactors were operated as simultaneous methanogenic-denitrifying (MD) units, whereas the other two were operated in partially aerated methanogenic (PAM) mode. In the first period, all bioreactors received a wastewater with 1 g chemical oxygen demand of methanol per liter (COD-methanol/L). In a second period, all the bioreactors received the wastewater plus 80 mg perchloroethylene (PCE)/L; at the start of period 2, one MD and one PAM were coupled to side sand-zero valent iron filters (ZVI). All bioreactors were inoculated with a microbial consortium not acclimated to PCE. In this work, the performance of the full period 1 and the first 60 days of period 2 is reported and discussed. The COD removal efficiency and the nitrate removal efficiency of the bioreactors essentially did not change between period 1 and period 2, i.e., upon PCE addition. On the contrary, specific methanogenic activity in PAM bioreactors (both with and without coupled ZVI filter) significantly decreased. This was consistent with a sharp fall of methane productivity in those bioreactors in period 2. During period 2, PCE removals in the range 86 to 97 % were generally observed; the highest removal corresponded to PAM bioreactors along with the highest dehalogenation efficiency (94 %). Principal component analysis as well as cluster analysis confirmed the trends mentioned above, i.e., the better performance of PAM over MD, and the unexpected no effect of the ZVI side filters on PCE removal and dehalogenation efficiencies. To the best of our knowledge, this is the first report on the combined treatment ZVI-biological of a water polluted with PCE, where the biological operation relied on simultaneous electron acceptors.

Empirical Bayes Ranking Methods

Ranking problems arise in setting priorities for investigations, in providing a simple summary of performance, in comparing objects in a manner robust to measurement scale, and in a wide variety of other applications. Commonly, rankings are computed from measurements that depend on the true attribute. Using the Gaussian model, we propose and compare methods for using these measurements to estimate the ranks of the underlying attributes and show that those based on an empirical Bayes model produce estimates that differ from ranking observed data. These differences result both from the effect of shrinking posterior means towards a common value by an amount that depends on the precision of individual measurements and from the Bayes processing of the posterior distribution to produce estimates that account for the uncertainty in the distribution of the ranks. We illustrate different ranking methods using data on school achievement reported by Aitkin and Longford (1986) . Mathematical and empirical results highlight the importance of using appropriate ranking methods and identify issues requiring further research.

No Association Between Unintentional Head Injuries and Early-Life Exposure to Tetrachloroethylene (PCE)-Contaminated Drinking Water

Objective:

Because of emerging evidence that early-life exposure to the solvent tetrachloroethylene (PCE) has long-lasting neurological consequences, we examined the risk of unintentional head injuries following prenatal and childhood exposure to PCE-contaminated drinking water.

Methods:

Participants provided information on head injuries and other relevant characteristics in a self-administered questionnaire. Exposure to PCE was modeled using a leaching and transport algorithm set in water system modeling software.

Results:

We did not observe any evidence of an increased risk of any type of head injury among exposed participants.

Conclusions:

PCE is a widespread water pollutant. Thus, documenting possible health effects of early-life exposure is vital for ensuring that drinking water regulations adequately protect vulnerable populations.

A systematic evaluation of the potential effects of trichloroethylene exposure on cardiac development

The 2011 EPA trichloroethylene (TCE) IRIS assessment, used developmental cardiac defects from a controversial drinking water study in rats (Johnson et al. [51]), along with several other studies/endpoints to derive reference values. An updated literature search of TCE-related developmental cardiac defects was conducted. Study quality, strengths, and limitations were assessed. A putative adverse outcome pathway (AOP) construct was developed to explore key events for the most commonly observed cardiac dysmorphologies, particularly those involved with epithelial-mesenchymal transition (EMT) of endothelial origin (EndMT); several candidate pathways were identified. A hypothesis-driven weight-of-evidence analysis of epidemiological, toxicological, in vitro, in ovo, and mechanistic/AOP data concluded that TCE has the potential to cause cardiac defects in humans when exposure occurs at sufficient doses during a sensitive window of fetal development. The study by Johnson et al. [51] was reaffirmed as suitable for hazard characterization and reference value derivation, though acknowledging study limitations and uncertainties.

Prenatal drinking-water exposure to tetrachloroethylene and ischemic placental disease: a retrospective cohort study

BACKGROUND

Prenatal drinking water exposure to tetrachloroethylene (PCE) has been previously related to intrauterine growth restriction and stillbirth. Pathophysiologic and epidemiologic evidence linking these outcomes to certain other pregnancy complications, including placental abruption, preeclampsia, and small-for-gestational-age (SGA) (i.e., ischemic placental diseases), suggests that PCE exposure may also be associated with these events. We examined whether prenatal exposure to PCE-contaminated drinking water was associated with overall or individual ischemic placental diseases.

METHODS

Using a retrospective cohort design, we compared 1,091 PCE-exposed and 1,019 unexposed pregnancies from 1,766 Cape Cod, Massachusetts women. Exposure between 1969 and 1990 was estimated using water distribution system modeling software. Data on birth weight and gestational age were obtained from birth certificates; mothers self-reported pregnancy complications.

RESULTS

Of 2,110 eligible pregnancies, 9% (N = 196) were complicated by ≥1 ischemic placental disease. PCE exposure was not associated with overall ischemic placental disease (for PCE ≥ sample median vs. no exposure, risk ratio (RR): 0.90; 95% confidence interval (CI): 0.65, 1.24), preeclampsia (RR: 0.36; 95% CI: 0.12-1.07), or SGA (RR: 0.98; 95% CI: 0.66-1.45). However, pregnancies with PCE exposure ≥ the sample median had 2.38-times the risk of stillbirth ≥27 weeks gestation (95% CI: 1.01, 5.59), and 1.35-times of the risk of placental abruption (95% CI: 0.68, 2.67) relative to unexposed pregnancies.

CONCLUSIONS

Prenatal PCE exposure was not associated with overall ischemic placental disease, but may increase risk of stillbirth.

Critical review of the epidemiologic literature regarding the association between congenital heart defects and exposure to trichloroethylene

The most recent Integrated Risk Information System review of trichloroethylene (TCE; CAS# 79-01-6) has suggested that congenital heart defects (CHD) are a critical endpoint associated with exposure to this solvent. This conclusion was drawn, at least partly, from epidemiologic data, including several relatively recent studies. The current article critically reviews this epidemiologic literature, focusing on study quality and consistency. Literature searches uncovered approximately a dozen studies that specifically addressed associations between TCE and congenital malformations in eight populations. Four of these reported positive associations between TCE and heart defects, with significant relative risks as high as 5-6 in some subgroups. However, each of the positive studies had substantial design or analytical flaws that could easily explain the results, thereby limiting the conclusions that can be drawn. Five studies found no positive association with TCE, and several of these reported substantially fewer cases than expected despite similar/higher exposures compared to positive studies, further detracting from causal conclusions. Overall, this epidemiologic literature provides no substantive or consistent evidence linking TCE to CHD.

Distance-based mapping of disease risk

In this article, we consider the problem of comparing the distribution of observations in a planar region to a pre-specified null distribution. Our motivation is a surveillance setting where we map locations of incident disease, aiming to monitor these data over time, to locate potential areas of high/low incidence so as to direct public health actions. We propose a non-parametric approach to distance-based disease risk mapping inspired by tomographic imaging. We consider several one-dimensional projections via the observed distribution of distances to a chosen fixed point; we then compare this distribution to that expected under the null and average these comparisons across projections to compute a relative-risk-like score at each point in the region. The null distribution can be established from historical data. Scores are displayed on the map using a color scale. In addition, we give a detailed description of the method along with some desirable theoretical properties. To further assess the performance of this method, we compare it to the widely used log ratio of kernel density estimates. As a performance metric, we evaluate the accuracy to locate simulated spatial clusters superimposed on a uniform distribution in the unit disk. Results suggest that both methods can adequately locate this increased risk but each relies on an appropriate choice of parameters. Our proposed method, distance-based mapping (DBM), can also generalize to arbitrary metric spaces and/or high-dimensional data.

Early lifestage exposure and potential developmental susceptibility to tetrachloroethylene

BACKGROUND

Tetrachloroethylene, also known as perchloroethylene or "perc", is a highly volatile and lipophilic solvent widely used in dry cleaning, textile processing, and metal-cleaning operations. The limited epidemiological and toxicological data available for exposure to perc during developmental lifestages, as well as the evidence for critical windows of exposure, highlight early life as a period of potential susceptibility.

METHODS

A literature search was performed to identify all peer-reviewed epidemiological and toxicologial studies examining outcomes from early lifestage exposure to perc, and reviewed by developmental stage for both exposure and outcome.

RESULTS

Exposure scenarios to perc unique to early lifestages include transplacental and breast milk intake, along with inhalation, ingestion, or dermal exposure. Toxicokinetics factors that may influence early lifestage susceptibility to perc, along with existing physiologically based pharmacokinetic (PBPK) models, are described. Adverse outcomes examined include: reproductive outcomes examined prior to conception including reduced fertility, adverse effects on sperm, or altered reproductive hormones; prenatal outcomes examined after exposure prior to conception or prenatally including fetal death, birth defects, and decreased birth weight; postnatal outcomes examined after exposure prior to conception, prenatally, or during childhood including neurotoxicity, immunotoxicity, cancer, hepatotoxicity, congential anomalies and mortality; and adult schizophrenia examined after exposure prior to conception.

CONCLUSIONS

The limited evidence on early lifestage exposure to perc does not provide sufficient evidence of this sensitive period as being more or less important than exposure at a later lifestage, such as during adulthood. However, there are a number of adverse health effects observed uniquely in early lifestages, and increased sensitivity to visual system deficits is suggested in children. Other outcomes observed in adults may not have been adequately assessed in children to directly compare sensitivity.

Altered cardiac function and ventricular septal defect in avian embryos exposed to low-dose trichloroethylene

Trichloroethylene (TCE) is the most frequently reported organic groundwater contaminant in the United States. It is controversial whether gestational TCE exposure causes congenital heart defects. The basis for TCE's proposed cardiac teratogenicity is not well understood. We previously showed that chick embryos exposed to 8 ppb TCE during cardiac morphogenesis have reduced cardiac output and increased mortality. To further investigate TCE's cardioteratogenic potential, we exposed in ovo chick embryos to TCE and evaluated the heart thereafter. Significant mortality was observed following TCE exposures of 8-400 ppb during a narrow developmental period (Hamburger-Hamilton [HH] stages 15-20, embryo day ED2.3-3.5) that is characterized by myocardial expansion, secondary heart looping, and endocardial cushion formation. Of the embryos that died, most did so between ED5.5 and ED6.5. Echocardiography of embryos at ED5.5 found that TCE-exposed hearts displayed significant functional and morphological heterogeneity affecting heart rate, left ventricular mass, and wall thickness. Individual embryos were identified with cardiac hypertrophy as well as with hypoplasia. Chick embryos exposed to 8 ppb TCE at HH17 that survived to hatch exhibited a high incidence (38%, p < 0.01, n = 16) of muscular ventricular septal defects (VSDs) as detected by echocardiography and confirmed by gross dissection; no VSDs were found in controls (n = 14). The TCE-induced VSDs may be secondary to functional impairments that alter cardiac hemodynamics and subsequent ventricular foramen closure, an interpretation consistent with recent demonstrations that TCE impairs calcium handling in cardiomyocytes. These data demonstrate that TCE is a cardiac teratogen for chick.

Prenatal exposure to tetrachloroethylene-contaminated drinking water and the risk of congenital anomalies: a retrospective cohort study

BACKGROUND

Prior animal and human studies of prenatal exposure to solvents including tetrachloroethylene (PCE) have shown increases in the risk of certain congenital anomalies among exposed offspring.

OBJECTIVES

This retrospective cohort study examined whether PCE contamination of public drinking water supplies in Massachusetts influenced the occurrence of congenital anomalies among children whose mothers were exposed around the time of conception.

METHODS

The study included 1,658 children whose mothers were exposed to PCE-contaminated drinking water and a comparable group of 2,999 children of unexposed mothers. Mothers completed a self-administered questionnaire to gather information on all of their prior births, including the presence of anomalies, residential histories and confounding variables. PCE exposure was estimated using EPANET water distribution system modeling software that incorporated a fate and transport model.

RESULTS

Children whose mothers had high exposure levels around the time of conception had an increased risk of congenital anomalies. The adjusted odds ratio of all anomalies combined among children with prenatal exposure in the uppermost quartile was 1.5 (95% CI: 0.9, 2.5). No meaningful increases in the risk were seen for lower exposure levels. Increases were also observed in the risk of neural tube defects (OR: 3.5, 95% CI: 0.8, 14.0) and oral clefts (OR 3.2, 95% CI: 0.7, 15.0) among offspring with any prenatal exposure.

CONCLUSION

The results of this study suggest that the risk of certain congenital anomalies is increased among the offspring of women who were exposed to PCE-contaminated drinking water around the time of conception. Because these results are limited by the small number of children with congenital anomalies that were based on maternal reports, a follow-up investigation should be conducted with a larger number of affected children who are identified by independent records.

Evidence of autoimmune-related effects of trichloroethylene exposure from studies in mice and humans

OBJECTIVE

Our objective was to examine experimental and epidemiologic studies pertaining to immune-related, and specifically autoimmune-related, effects of trichloroethylene (TCE).

DATA SOURCES AND EXTRACTION

We performed a literature search of PubMed and reviewed bibliographies in identified articles. We then systematically reviewed immune-related data, focusing on clinical and immunologic features and mechanistic studies.

DATA SYNTHESIS

Studies conducted in MRL+/+ lupus mice report an accelerated autoimmune response in relation to exposure to TCE or some metabolites. Effects have been reported after 4 weeks of exposure to TCE at doses as low as 0.1 mg/kg/day in drinking water and have included increased antinuclear antibodies and interferon-gamma (IFN-gamma) and decreased secretion of interleukin-4 (IL-4), consistent with an inflammatory response. Autoimmune hepatitis, inflammatory skin lesions, and alopecia have been found after exposures of 32-48 weeks. Recent mechanistic experiments in mice examined oxidative stress and, specifically, effects on lipid-peroxidation-derived aldehydes in TCE-induced autoimmune disease. Two studies in humans reported an increase in IL-2 or IFN-gamma and a decrease in IL-4 in relation to occupational or environmental TCE exposure. Occupational exposure to TCE has also been associated with a severe, generalized hypersensitivity skin disorder accompanied by systemic effects, including hepatitis. In three case-control studies of scleroderma with a measure of occupational TCE exposure, the combined odds ratio was 2.5 [95% confidence interval (CI), 1.1-5.4] in men and 1.2 (95% CI, 0.58-2.6) in women.

CONCLUSION

The consistency among the studies and the concordance between the studies in mice and humans support an etiologic role of TCE in autoimmune disease. Multisite collaborations and studies of preclinical immune markers are needed to further develop this field of research.

Exposure to Tetrachloroethylene-Contaminated Drinking Water and the Risk of Pregnancy Loss

There is little information on the impact of solvent-contaminated drinking water on pregnancy outcomes. This retrospective cohort study examined whether maternal exposure to tetrachloroethylene (PCE) - contaminated drinking water in the Cape Cod region of Massachusetts influenced the risk of clinically recognized pregnancy loss. The study identified exposed (n=959) and unexposed (1,087) women who completed a questionnaire on their residential and pregnancy histories, and confounding variables. Exposure was estimated using water distribution system modeling software. No meaningful associations were seen between PCE exposure level and the risk of clinically recognized pregnancy loss at the exposure levels experienced by the study population. Because PCE remains a common water contaminant, it is important to continue monitoring its impact on women and their pregnancies.

Prenatal exposure to tetrachloroethylene-contaminated drinking water and the risk of adverse birth outcomes

BACKGROUND

Prior studies of prenatal exposure to tetrachloroethylene (PCE) have shown mixed results regarding its effect on birth weight and gestational age.

OBJECTIVES

In this retrospective cohort study we examined whether PCE contamination of public drinking-water supplies in Massachusetts influenced the birth weight and gestational duration of children whose mothers were exposed before the child's delivery.

METHODS

The study included 1,353 children whose mothers were exposed to PCE-contaminated drinking water and a comparable group of 772 children of unexposed mothers. Birth records were used to identify subjects and provide information on the outcomes. Mothers completed a questionnaire to gather information on residential histories and confounding variables. PCE exposure was estimated using EPANET water distribution system modeling software that incorporated a fate and transport model.

RESULTS

We found no meaningful associations between PCE exposure and birth weight or gestational duration. Compared with children whose mothers were unexposed during the year of the last menstrual period (LMP), adjusted mean differences in birth weight were 20.9, 6.2, 30.1, and 15.2 g for children whose mothers' average monthly exposure during the LMP year ranged from the lowest to highest quartile. Similarly, compared with unexposed children, adjusted mean differences in gestational age were -0.2, 0.1, -0.1, and -0.2 weeks for children whose mothers' average monthly exposure ranged from the lowest to highest quartile. Similar results were observed for two other measures of prenatal exposure.

CONCLUSIONS

These results suggest that prenatal PCE exposure does not have an adverse effect on these birth outcomes at the exposure levels experienced by this population.

Trichloroethylene and ocular malformations: analysis of extant literature

An evaluation of the scientific literature for trichloroethylene (TCE) identified two reports of ocular defects, specifically microphthalmia/anophthalmia, following prenatal TCE exposure in rats. Herein, these reports are analyzed in detail and interpreted within the context of other developmental TCE exposure studies. The ocular findings following prenatal TCE exposure are reported in studies that were not designed specifically for developmental safety assessment, and thus did not use standard experimental practices. Furthermore, these findings most commonly occurred at TCE doses associated with considerable maternal toxicity. Among the 18 published studies using developmental TCE exposures, only 3 used doses sufficiently high enough to result in maternal toxicity, and of these, only the 2 discussed in detail in this paper demonstrated ocular defects in the offspring. Furthermore, statistically significant effects were only observed at doses that were above the currently accepted guideline limit dose of 1000 mg/kg body weight. All other TCE developmental exposure studies failed to demonstrate ocular defects as a result of prenatal exposure. These results suggest that the micro-/anophthalmia findings were likely a consequence of delivery of an extremely high bolus TCE dose that is irrelevant to human environmental exposure scenarios.

Trichloroethylene and dichloroethylene: a critical review of teratogenicity

Trichloroethylene (TCE) and dichloroethylene (DCE) are high-volume industrial chemicals frequently found as contaminants in public drinking water supplies. The developmental toxicity of both chemicals has been evaluated in laboratory and epidemiologic studies. It has been suggested that TCE and DCE are specific cardiac teratogens and that drinking water contaminated with them increases the risk of congenital heart defects in exposed human populations. In contrast, other laboratory and epidemiologic studies do not find an increase in developmental effects, either in general or specifically affecting the heart. This laboratory and epidemiologic base was reviewed to evaluate the strengths and weaknesses of the conflicting published reports. We conclude that the weight of experimental and epidemiologic evidence does not support the hypothesis that TCE or DCE is a selective developmental toxicant in general or a cardiac teratogen specifically.

Community clusters of childhood leukemia and lymphoma: evidence of infection?

Information suggesting that infection may be an underlying cause of childhood leukemia and lymphoma includes the occasional appearance of cases in time-space clusters within communities and increased incidence after communities experience marked population influxes (population mixing). Among 50 clusters involving cases of childhood leukemia and lymphoma investigated in the United States in 1961-1977, eight showed suggestive evidence of underlying infectious causation. In seven of the eight communities, case occurrence was associated with the attendance of patients or their siblings at particular schools or with family participation in particular church groups. In five, rapid population growth had occurred. Other findings included the possible association of cases with unusual patterns of infectious disease (rheumatic illness in one community, chickenpox in another) and with other childhood diseases, including other forms of childhood cancer. In one community, two cases of Burkitt's lymphoma occurred at the same time, and a third case arose 3 years later in boys living in a newly developing neighborhood. Such community observations support the need for continued biologic research regarding the possible role of infectious agents in childhood leukemia and lymphoma.

Probability estimates for the unique childhood leukemia cluster in Fallon, Nevada, and risks near other U.S. Military aviation facilities

A unique cluster of childhood leukemia has recently occurred around the city of Fallon in Churchill County, Nevada. From 1999 to 2001, 11 cases were diagnosed in this county of 23,982 people. Exposures related to a nearby naval air station such as jet fuel or an infectious agent carried by naval aviators have been hypothesized as potential causes. The possibility that the cluster could be attributed to chance was also considered. We used data from the Surveillance, Epidemiology, and End Results Program (SEER) to examine the likelihood that chance could explain this cluster. We also used SEER and California Cancer Registry data to evaluate rates of childhood leukemia in other U.S. counties with military aviation facilities. The age-standardized rate ratio (RR) in Churchill County was 12.0 [95% confidence interval (CI), 6.0-21.4; p = 4.3 times symbol 10(-9)]. A cluster of this magnitude would be expected to occur in the United States by chance about once every 22,000 years. The age-standardized RR for the five cases diagnosed after the cluster was first reported was 11.2 (95% CI, 3.6-26.3). In contrast, the incidence rate was not increased in all other U.S. counties with military aviation bases (RR = 1.04; 95% CI, 0.97-1.12) or in the subset of rural counties with military aviation bases (RR = 0.72; 95% CI, 0.48-1.08). These findings suggest that the Churchill County cluster was unlikely due to chance, but no general increase in childhood leukemia was found in other U.S. counties with military aviation bases.

The impact of environmental pollution on congenital anomalies

Major congenital anomalies are diagnosed in 2-4% of births. In this paper we review epidemiological studies that have specifically looked at congenital anomalies as a possible outcome of community exposure to chemical exposures associated with environmental pollution. These include studies of drinking water contaminants (heavy metals and nitrates, chlorinated and aromatic solvents, and chlorination by-products), residence near waste disposal sites and contaminated land, pesticide exposure in agricultural areas, air pollution and industrial pollution sources, food contamination, and disasters involving accidental, negligent or deliberate chemical releases of great magnitude. We conclude that there are relatively few environmental pollution exposures for which we can draw strong conclusions about the potential to cause congenital anomalies and, if so, the chemical constituents implicated, to provide an evidence base for public health and clinical practice. A precautionary approach should be adopted at both community and individual level. In order to prevent congenital anomalies, one must reduce exposure to potential teratogens before pregnancy is recognized (i.e. preconceptionally and in the first few weeks of pregnancy). It is a challenge to develop effective strategies for preconceptional care within the primary care framework. Prenatal service providers and counsellors need to be aware of the uncertainties regarding environmental pollution when addressing parental concerns.

Things to know and do about cancer clusters

Perceived cancer clusters present difficulties and opportunities for clinicians and public health officials alike. Public health officials receive reports of perceived cancer clusters, evaluate the validity of these reports, and/or launch investigations to identify potential causes. Clinicians interact directly with the affected patients, families, or community representatives who question the occurrence of cancer and the underlying causes. Clinicians may identify cancer clusters when they question the unusual occurrence of a rare form of cancer within their practice or community. In addition, clinicians may be asked to discuss cancer clusters and inform local debates. In this paper, we describe the public health practice experience with cancer clusters and identify cancer prevention and control opportunities for clinicians and public health officials. Scientific investigations of cancer clusters rarely uncover new knowledge about the causes of cancer. However, a set of common characteristics, unique to etiologic cluster investigations have uncovered new information about the causes of cancer or demonstrated a preventable link to a known carcinogen. These characteristics may provide useful clues for sorting out the small number of clusters worthy of further scientific investigation. Public awareness of cancer clusters may promote an opportunity to inform and motivate people about the preventable causes of cancer and effective cancer screening methods.

Environmental health surveillance: indicators for freshwater ecosystems

The relationship between the health of human populations and the state of the ecosystems in which they live is profoundly complex. As most environmental indicators relevant to human health depend on evidence of a direct cause and effect relationship, there are few indicators of the less direct consequences of environmental degradation on human health. Indicators of the direct consequence of contaminants in freshwater ecosystems on human health are highlighted in this paper and candidate indicators for environmental health are provided. Many of the indicators included here are from the State Of the Lakes Ecosystem Conference (SOLEC) program. SOLEC conferences in the past (1994 and 1996) examined the state of various components of the ecosystem through the use of ad hoc indicators, and provided subjective assessments of certain environmental conditions. At SOLEC 98, a comprehensive suite of 80 Great Lakes ecosystem health indicators was presented for review, refinement and acceptance. Candidate indicators for freshwater systems and environmental health presented here are organized following the "Pressure-State-Response" framework and cover the areas of drinking water, recreational water, freshwater food sources, and the availability of freshwater for economic activities.

Toxicity of trichloroethylene following inhalation and drinking contaminated water

The neurobehavioural effects of trichloroethylene (TCE) were studied in rats following administration of the solvent orally (350, 700 and 1400 ppm in drinking water for 90 days) and through inhalation (376 ppm for 4 h a day, 5 days per week for 180 days). Various aspects of spontaneous locomotor activity were assessed at different periods after exposure through either of the routes. Oral exposure to TCE had no significant effect on spontaneous locomotor activity or cognitive ability, whereas inhalation to the solvent resulted in an increase in the distance travelled and horizontal activity counts at day 30 but a decrease at day 60 of exposure. The time spent in ambulatory and stereotypic movements as well as the number of stereotypic movements were enhanced significantly only at day 30. The resting time was decreased at day 30 but enhanced at day 60 of exposure. The learning ability was not affected significantly up to day 180. The results highlight the neurotoxic potential of inhalation exposure to TCE.

Dermal benzene and trichloroethylene induce aneuploidy in immature hematopoietic subpopulations in vivo

Accumulation of genetic damage in long-lived cell populations with proliferative capacity is implicated in tumorigenesis. Hematopoietic stem cells (hsc) maintain lifetime hematopoiesis, and recent studies demonstrate that hsc in leukemic patients are cytogenetically aberrant. We postulated that exposure to agents associated with increased leukemia risk would induce genomic changes in cells in the hsc compartment. Aneusomy involving chromosomes 2 and 11 in sorted hsc (Lin(-)c-kit(+)Sca-1(+)) and maturing lymphoid and myeloid cells from mice that received topical doses of benzene (bz) or trichloroethylene (TCE) was quantified using fluorescence in situ hybridization. Six days after bz or TCE exposure, aneuploid cells in the hsc compartment increase four- to eightfold in a dose- and schedule-independent manner. Aneuploid lymphoid and myeloid cells from bz- and TCE-treated mice approximate controls, except after repeated benzene exposures. Aneuploid cells are more frequent in the hsc compartment than in mature hematopoietic subpopulations. Hematotoxicity was also quantified in bz- and TCE-exposed hematopoietic subpopulations using two colony-forming assays: CFU-GM (colony-forming units/granulocyte-macrophage progenitors) and CAFC (cobblestone area-forming cells). Data indicate that bz is transiently cytotoxic (< or =1 week) to hsc subpopulations, and induces more persistent toxicity (>2 weeks) in maturing, committed progenitor subpopulations. TCE is not hematotoxic at the doses applied. In conclusion, we provide direct evidence for induction of aneuploidy in cells in the hsc compartment by topical exposure to bz and TCE. Disruption of genomic integrity and/or toxicity in hsc subpopulations may be one step in leukemic progression.

A civil action and statistical assessments of the spatial pattern of disease: do we have a cluster?

A reported "cluster" of excess childhood leukemia cases and possible environmental causes in Woburn, Massachusetts, formed a key motivation for the events described in the popular book and motion picture A Civil Action. Although statistical methods to assess spatial clustering existed prior to the events in Woburn, increasing interest in environmental risk factors and recent developments in geographical information systems and data availability prompt increased attention to such methods and their application to public health data. In this article, we review statistical and epidemiological concepts involved in the analysis of disease clusters. We discuss data issues, outline some methodological approaches, and illustrate ideas using data regarding leukemia incidence in upstate New York for the years 1978-1982.

Trichloroethylene and cancer: epidemiologic evidence

Trichloroethylene is an organic chemical that has been used in dry cleaning, for metal degreasing, and as a solvent for oils and resins. It has been shown to cause liver and kidney cancer in experimental animals. This article reviews over 80 published papers and letters on the cancer epidemiology of people exposed to trichloroethylene. Evidence of excess cancer incidence among occupational cohorts with the most rigorous exposure assessment is found for kidney cancer (relative risk [RR] = 1.7, 95% confidence interval [CI] 1.1-2.7), liver cancer (RR = 1.9, 95% CI(1.0-3.4), and non-Hodgkin's lymphoma (RR = 1.5, 95% CI 0.9-2.3) as well as for cervical cancer, Hodgkin's disease, and multiple myeloma. However, since few studies isolate trichloroethylene exposure, results are likely confounded by exposure to other solvents and other risk factors. Although we believe that solvent exposure causes cancer in humans and that trichloroethylene likely is one of the active agents, we recommend further study to better specify the specific agents that confer this risk and to estimate the magnitude of that risk.

Health effects of residence near hazardous waste landfill sites: a review of epidemiologic literature

This review evaluates current epidemiologic literature on health effects in relation to residence near landfill sites. Increases in risk of adverse health effects (low birth weight, birth defects, certain types of cancers) have been reported near individual landfill sites and in some multisite studies, and although biases and confounding factors cannot be excluded as explanations for these findings, they may indicate real risks associated with residence near certain landfill sites. A general weakness in the reviewed studies is the lack of direct exposure measurement. An increased prevalence of self-reported health symptoms such as fatigue, sleepiness, and headaches among residents near waste sites has consistently been reported in more than 10 of the reviewed papers. It is difficult to conclude whether these symptoms are an effect of direct toxicologic action of chemicals present in waste sites, an effect of stress and fears related to the waste site, or an effect of reporting bias. Although a substantial number of studies have been conducted, risks to health from landfill sites are hard to quantify. There is insufficient exposure information and effects of low-level environmental exposure in the general population are by their nature difficult to establish. More interdisciplinary research can improve levels of knowledge on risks to human health of waste disposal in landfill sites. Research needs include epidemiologic and toxicologic studies on individual chemicals and chemical mixtures, well-designed single- and multisite landfill studies, development of biomarkers, and research on risk perception and sociologic determinants of ill health.

Agency for Toxic Substances and Disease Registry's 1997 priority list of hazardous substances. Latent effects--carcinogenesis, neurotoxicology, and developmental deficits in humans and animals

In support of Superfund re-authorization legislation, the Division of Toxicology of the Agency for Toxic Substances and Disease Registry (ATSDR) prepared a chemical-specific consultation document for Congress that identified those chemicals with carcinogenic, neurological, or developmental adverse effects having a latency period longer than 6 years. The review was limited to the top 50 substances listed on ATSDR's 1997 Priority List of Hazardous Substances (Priority List). Among the top 50 chemicals, a review of the technical literature indicated that 38 (76%) were classified as "reasonably anticipated," "possibly," or "probably" capable of causing cancer in humans, based either on human and animal data. Eight chemicals (16%) had well-established cancer latency periods in humans of 6 years or more following exposure. Three substances (6%)--arsenic, creosote, and benzidine--had data indicating latency periods longer than 6 years. The technical literature review likewise confirmed the potential for neurological and developmental effects with a latency of 6 years. Twenty-seven (54%) of the top 50 substances caused acute and/or chronic neurotoxic effects; a number of these also caused neurological effects that persisted beyond 6 years (or the equivalent in animal studies) such as: behavioral problems, neurological deficiencies, reduced psychomotor development, cognitive deficiencies, and reduced IQ. Twenty-eight substances (56%) caused adverse developmental effects in offspring of exposed individuals or animals including increased fetal and infant mortality, decreased birth weights and litter sizes, and growth delays. Latency periods for related chemicals are expected to be similar due to structural and toxicological similarities.

A review of the effects of hazardous waste on reproductive health

Approximately 1 in 4 Americans lives within 4 miles of a hazardous waste site according to the Environmental Protection Agency. In light of this large proportion and the public's high level of concern that hazardous waste causes health problems, it is important for primary care physicians and other health care providers to know that residential proximity to some kinds of hazardous waste sites is associated with adverse reproductive effects. Findings from both state-based surveillance programs and studies of individual hazardous waste sites have shown increased risk of congenital malformations and reductions in birth weight among infants born to parents living near hazardous waste sites. This article summarizes salient literature on human health effects of hazardous waste and suggests actions for primary care providers to consider.

Exposure to trihalomethanes and adverse pregnancy outcomes

Exposure during pregnancy to disinfection by-products in drinking water has been hypothesized to lead to several adverse reproductive outcomes. We performed a retrospective cohort study to examine the relation of trihalomethane exposure during the third trimester of pregnancy to low birthweight, term low birthweight, and preterm delivery. We matched Colorado birth certificates from January 1, 1990, through December 31, 1993, to historical water sample data with respect to time and location of maternal residence based on census block groups. After excluding births from all census block groups with no trihalomethane sample data and restricting to singleton white births with 28-42 weeks of completed gestation (>400 gm), we studied 1,893 livebirths within 28 census block groups. We found a weak association of trihalomethane exposure during the third trimester with low birthweight (odds ratio = 2.1 for the highest exposure level; 95% confidence interval = 1.0-4.8); a large increase in risk for term low birthweight at the highest level of exposure (odds ratio = 5.9; 95% confidence interval = 2.0-17.0); and no association between exposure and preterm delivery (odds ratio = 1.0 for the highest exposure level; 95% confidence interval = 0.3-2.8). The small number of adverse outcomes reduced the precision of risk estimates, but these data indicate a potentially important relation between third trimester exposure to trihalomethanes and retarded fetal growth.

Time-dependent autoimmune response of dichloroacetyl chloride in female MRL +/+ mice

Welders are exposed to dichloroacetyl chloride (DCAC) when trichloroethene (TCE) is used as a degreasing agent. Human exposure to TCE and tetrachloroethane can also lead to formation of DCAC in situ through metabolism. Due to its strong acylating property, it can bind with cellular macromolecules and act as hapten and consequently may elicit autoimmune (Al) response. Earlier, we reported that both TCE and DCAC induce/accelerate Al response in MRL +/+ mice, and DCAC even at 50 fold lower concentration induced greater Al responses. These studies, however, were conducted at a single time point (six weeks of treatment) and therefore necessitate a time-dependent characterization of this DCAC-induced Al response. Female MRL +/+ were given ip treatments of 0.2 mmol/kg DCAC in 100 microliters of corn oil every 4th day, while controls received an equal volume of corn oil only. DCAC treatment resulted in spleen weight increases at all time points whereas serum IgG showed significant increases at 4, 6 and 8 weeks of treatment. Serum autoantibodies, i.e., antinuclear antibodies, anti-single stranded DNA antibodies and anticardiolipin antibodies showed positive responses only after 4 weeks of treatment. However, the optimal responses were observed at 6 weeks and subsequently the responses diminished (at 8 weeks). The DCAC-specific antibodies showed a pattern similar to autoantibodies, i.e., an optimal response at 6 weeks of treatment. Our results thus suggest that DCAC under the current experimental conditions induces an optimal Al response at 6 weeks of treatment and further emphasize the usefulness of MRL +/+ mice in studying chemical-induced autoimmunity.

Molecular epidemiology study of a suspected community cluster of childhood cancers

We investigated the report of a community cluster of cancers in 33 children, which included two siblings known to have dominantly inherited Li-Fraumeni syndrome and a germline p53 mutation. After defining criteria for inclusion in the cluster, the 12 eligible childhood cancer probands diagnosed between 1980 and 1989 were not excessive (expected, ten cases). The corresponding childhood cancer mortality rates for the community fluctuated between 1950 and 1989 and were not increased overall. However, three additional probands had family histories of childhood cancer that suggested a forme fruste of Li-Fraumeni syndrome. The epidemiological data suggested a geographic cluster of this rare hereditary disorder, but absence of germline p53 mutation in the three other multicase families indicates genetic heterogeneity. Laboratory studies can assist analyses of suspected clusters, although investigations of geographic clusters of hereditary cancers raise complex issues of confidentiality and protection of affected individuals, their families, and the community.

The power of focused tests to detect disease clustering

Statistical tests have been proposed for determining whether incident cases of adverse health effects are 'clustered' together. Several procedures, termed 'focused', specifically analyse disease surveillance data around pre-specified putative sources of environmental hazard. Little has been done to compare the performance of various proposed methods on actual models of clustering. Analytic power functions are derived for three tests of focused clustering. These functions are based on the probabilistic structure of the clustering tests and do not require simulation. The three tests are compared with respect to statistical power on hypothetical data where monotone multiplicative increases in disease risk near a putative hazard define disease clusters of varying intensity.

Spontaneous abortion in a hospital population: are tobacco and coffee intake risk factors?

The objective of this study was to examine the possible relationships between spontaneous abortion and caffeine, tobacco and alcohol intake in a well-controlled group of hospital workers. A retrospective cohort study design including 711 women, 20 to 41 years old, was used. All data regarding the purpose of this study were extracted from clinical histories registered at the Preventive Medicine Service. The dependent variable was spontaneous abortion and the independent variables were tobacco, coffee, and alcohol intake. Age, previous spontaneous abortion, menarcheal age and marital status were considered as potential confounders. The data were analyzed by multiple logistic regression. The following adjusted odds ratios of spontaneous abortion by caffeine consumption were calculated: 141-280 mg/day, 2.20 (1.22-3.96); 281-420 mg/day, 4.81 (2.28-10.14) and 421 or more, 15.43 (7.38-32.43); p < 0.05. The adjusted odds ratio for tobacco were 11 or more cigarettes/day, 3.35 (1.65-6.92); p < 0.05. It appears from this and other papers that tobacco and caffeine intake must be considered as clear risk factors for spontaneous abortion or miscarriage.

Case-control study on the association between a cluster of childhood haematopoietic malignancies and local environmental factors in Aalsmeer, The Netherlands

STUDY OBJECTIVE AND DESIGN

In Aalsmeer, a horticultural community near the main international airport in The Netherlands, a more than fourfold increase in the incidence of haematopoietic malignancies in young people was observed between 1980 and 1985. In a population based case-control study, the association with local environmental factors was investigated.

PARTICIPANTS

For each patient younger than 40 years of age (n = 14) diagnosed between 1975 and 1989, four age and sex matched controls were selected via local general practitioners.

METHODS

All parents of patients and controls completed a questionnaire on their lifestyle, living conditions, and health, for several years preceding each individual diagnosis. Odds ratios (ORs) with 95% confidence intervals (CI) were calculated, matched, and, if necessary, stratified for neighbourhood.

MAIN RESULTS

Increased ORs were recorded for intensive use of petroleum products and pesticides by the patients themselves and their fathers: OR petroleum products: 8.0 (95% CI 2.2, 129.9) and 9.0 (1.0, 66.1) respectively; OR pesticides: 6.0 (0.6, 49.3) and 3.2 (1.0, 10.1) respectively. Swimming in a local pond was also significantly associated with the disease: OR = 5.3 (1.3, 17.4). In the 1970s this pond had been polluted by petroleum products and pesticides.

CONCLUSIONS

The increased incidence of childhood haematopoietic malignancies in Aalsmeer may have been associated with several specific local environmental factors. Interpretation of the results, however, should take into account the fact that confidence intervals were wide because of the limited number of cases.

Chlorinated hydrocarbon solvents: substituting our way toward human carcinogenicity

A discussion of the history of substitutions in industrial solvent use is presented, and animal carcinogenicity studies with certain chlorinated hydrocarbon solvents are reviewed. The present knowledge on the association between occupational exposure to chlorinated hydrocarbon solvents and human carcinogenicity is summarized, including a critical review of 23 studies pertaining to human carcinogenicity. Several deficiencies are identified in these studies that make interpretation of the results uncertain, including poor characterization of exposures in qualitative and quantitative terms, the small numbers of deaths or cases, and short follow-up periods. Despite these weaknesses, we conclude that, when viewed collectively, the evidence strongly suggests that occupational exposures to chlorinated hydrocarbon solvents are associated with an excess human cancer risk. The literature supports an association between occupational exposures to chlorinated hydrocarbons and elevated risks of leukemia, lymphoma, and urinary tract cancer. Parental occupational exposures are consistently associated with an elevated childhood cancer risk in the offspring.