A case-control study of childhood leukemia in Woburn, Massachusetts: the relationship between leukemia incidence and exposure to public drinking water

Trichloroethylene exposure, multi-organ injury, and potential mechanisms: A narrative review

Trichloroethylene (TCE) is a common environmental pollutant and industrial chemical that has been associated with adverse health effects, especially on organ systems. The purpose of this review is to summarize the current findings on organ system damage caused by TCE exposure and the underlying mechanisms involved. Numerous studies have shown that TCE exposure may cause damage to multiple organ systems, mainly the skin, liver, kidney, and circulatory system. The mechanisms leading to TCE-induced organ system damage are complex and diverse. TCE is metabolized in vivo to reactive intermediates, through which TCE can induce oxidative stress, interfere with cell signaling pathways, and promote inflammatory responses. In addition, studies have shown that TCE interferes with DNA repair mechanisms, leading to genotoxicity and potentially carcinogenic effects. This review highlights the importance of understanding the deleterious effects of TCE exposure on organ systems and provides insights into the underlying mechanisms involved. Further research is needed to elucidate the full range of organ system damage caused by TCE and to develop effective prevention and treatment strategies.

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.

Pediatric Cancer By Race, Ethnicity and Region in the United States

BACKGROUND

In a 2018 descriptive study, cancer incidence in children (age 0-19) in diagnosis years 2003 to 2014 was reported as being highest in New Hampshire and in the Northeast region.

METHODS

Using the Cancer in North America (CiNA) analytic file, we tested the hypotheses that incidence rates in the Northeast were higher than those in other regions of the United States either overall or by race/ethnicity group, and that rates in New Hampshire were higher than the Northeast region as a whole.

RESULTS

In 2003 to 2014, pediatric cancer incidence was significantly higher in the Northeast than other regions of the United States overall and among non-Hispanic Whites and Blacks, but not among Hispanics and other racial minorities. However, there was no significant variability in incidence in the states within the Northeast overall or by race/ethnicity subgroup. Overall, statistically significantly higher incidence was seen in the Northeast for lymphomas [RR, 1.15; 99% confidence interval (CI), 1.10-1.19], central nervous system neoplasms (RR, 1.12; 99% CI, 1.07-1.16), and neuroblastoma (RR, 1.13; 99% CI, 1.05-1.21).

CONCLUSIONS

Pediatric cancer incidence is statistically significantly higher in the Northeast than in the rest of the United States, but within the Northeast, states have comparable incidence. Differences in cancer subtypes by ethnicity merit further investigation.

IMPACT

Our analyses clarify and extend previous reports by statistically confirming the hypothesis that the Northeast has the highest pediatric cancer rates in the country, by providing similar comparisons stratified by race/ethnicity, and by assessing variability within the Northeast.

Health Misinformation about Toxic-Site Harm: The Case for Independent-Party Testing to Confirm Safety

Health misinformation can cause harm if regulators or private remediators falsely claim that a hazardous facility is safe. This misinformation especially threatens the health of children, minorities, and poor people, disproportionate numbers of whom live near toxic facilities. Yet, perhaps because of financial incentives, private remediators may use safety misinformation to justify reduced cleanup. Such incentives exist in nations like the United States, where most toxic-site testing/remediation is semi-privatized or voluntary, conducted by private parties, commercial redevelopers, who can increase profits by underestimating health harm, thus decreasing required testing/remediation. Our objective is to begin to determine whether or not interested parties misrepresent health harm (at hazardous facilities that they test/remediate/redevelop) when they use traditional and social media to claim that these sites are safe. Our hypothesis is that, contrary to the safety claims of the world’s largest commercial developer, Coldwell Banker Real Estate/Trammell Crow (CBRE/TCC), the authors’ screening assessment, especially its lab-certified, toxic-site, indoor-air tests, show violations of all three prominent government, cancer-safety benchmarks. If so, these facilities require additional testing/remediation, likely put site renters at risk, and may reveal problems with privatized hazardous cleanup. To our knowledge, we provide the first independent tests of privatized, toxic-site assessments before cancer reports occur. Our screening assessment of this hypothesis tests indoor air in rental units on a prominent former weapons-testing site (the US Naval Ordnance Testing Station, Pasadena, California (NOTSPA) that is subject to carcinogenic vapor intrusion by volatile organic compounds, VOCs), then compares test results to the redeveloper’s site-safety claims, made to government officials and citizens through traditional and social media. Although NOTSPA toxic soil-gas concentrations are up to nearly a million times above allowed levels, and indoor air was never tested until now, both the regulator and the remediator (CBRE/TCC) have repeatedly claimed on social media that “the site is safe at this time.” We used mainly Method TO-17 and two-week sampling with passive, sorbent tubes to assess indoor-air VOCs. Our results show that VOC levels at every location sampled—all in occupied site-rental units—violate all three government-mandated safety benchmarks: environmental screening levels (ESLs), No Significant Risk Levels (NSRLs), and inhalation risks based on the Inhalation Unit Risk (IUR); some violations are two orders of magnitude above multiple safety benchmarks. These results support our hypothesis and suggest a need for independent assessment of privatized cleanups and media-enhanced safety claims about them. If our results can be replicated at other sites, then preventing health misinformation and toxic-facility safety threats may require new strategies, one of which we outline.

Data-Quality Assessment Signals Toxic-Site Safety Threats and Environmental Injustices

Most hazardous-waste sites are located in urban areas populated by disproportionate numbers of children, minorities, and poor people who, as a result, face more severe pollution threats and environmental-health inequalities. Partly to address this harm, in 2017 the United Nations unanimously endorsed the New Urban Agenda, which includes redeveloping urban-infill-toxic-waste sites. However, no systematic, independent analyses assess the public-health adequacy of such hazardous-facility redevelopments. Our objective is to provide a preliminary data-quality assessment (PDQA) of urban-infill-toxic-site testing, conducted by private redevelopers, including whether it adequately addresses pollution threats. To this end, we used two qualitative, weight-of-evidence methods. Method 1 employs nine criteria to select assessments for PDQA and help control for confounders. To conduct PDQA, Method 2 uses three US Environmental Protection Agency standards—the temporal, geographical, and technological representativeness of sampling. Our Method 1 results reveal four current toxic-site assessments (by CBRE/Trammell Crow, the world’s largest commercial developer); at all of these sites the main risk drivers are solvents, volatile organic compounds, including trichloroethylene. Our Method 2 results indicate that all four assessments violate most PDQA standards and systematically underestimate health risk. These results reveal environmental injustice, disproportionate health threats to children/minorities/poor people at all four sites. Although preliminary, our conclusion is that alleviating harm and environmental-health inequalities posed by urban-infill-toxic-site pollution may require improving both the testing/cleanup/redevelopment requirements of the New Urban Agenda and the regulatory oversight of assessment and remediation performed by private redevelopers.

Spatial Outcomes of Soft Tissue Sarcoma in Southern West Virginia

Introduction Dioxins, polychlorinated biphenyls (PCBs), and 2,3,7,8-Tetrachlorodibenzodioxin (TCDDs) are persistent organic pollutants widely distributed in the food chain. For over 50 years, the Monsanto plant in Nitro, West Virginia, created dioxin waste while producing herbicides, Agent Orange (during the Vietnam War), and different forms of rubber. Recent and past literature has established a link between the Monsanto plant and increased cancer cases within the region. Soft tissue sarcoma is one of the few specific cancers that has been linked to dioxin exposure. This pilot study examined whether sarcoma cases were clustered or randomly distributed within Kanawha County, West Virginia over the years 2000 to 2013. We hypothesize that sarcoma cancer cases will be spatially clustered. Methods This study assessed the spatial distribution of cancer patients with addresses within the Nitro, West Virginia, and study area. The Charleston Area Medical Center shared soft tissue sarcoma (n = 97) cases from 2000 to 2013. An unweighted K function with confidence intervals (99 Monte Carlo permutations) and 10 distance at 2800 meters each band analyzed the distribution of cases. Results The results suggest that sarcoma cases are slightly clustered within the study area. The region also has a high concentration of chemical and industrial sites. The eighth distance band exhibited the greatest difference (11384), between the expected versus the observed K function. Conclusion The unweighted K function shows non-random clustering. Future studies could investigate possible associations to industrial, chemical, or other possible point source contamination within the study area.

Identification of significant risks in pediatric acute lymphoblastic leukemia (ALL) through machine learning (ML) approach

Pediatric acute lymphoblastic leukemia (ALL) through machine learning (ML) technique was analyzed to determine the significance of clinical and phenotypic variables as well as environmental conditions that can identify the underlying causes of child ALL. Fifty pediatric patients (n = 50) included who were diagnosed with acute lymphoblastic leukemia (ALL) according to the inclusion and exclusion criteria. Clinical variables comprised of the blood biochemistry (CBC, LFTs, RFTs) results, and distribution of type of ALL, i.e., T ALL or B ALL. Phenotypic data included the age, sex of the child, and consanguinity, while environmental factors included the habitat, socioeconomic status, and access to filtered drinking water. Fifteen different features/attributes were collected for each case individually. To retrieve most useful discriminating attributes, four different supervised ML algorithms were used including classification and regression trees (CART), random forest (RM), gradient boosted machine (GM), and C5.0 decision tree algorithm. To determine the accuracy of the derived CART algorithm on future data, a ten-fold cross validation was performed on the present data set. The ALL was common in children of age below 5 years in male patients whole belonged to middle class family of rural areas. (B-ALL) was most frequent as compared with T-ALL. The consanguinity was present in 54% of cases. Low levels of platelets and hemoglobin and high levels of white blood cells were reported in child ALL patients. CART provided the best and complete fit for the entire data set yielding a 99.83% model fit accuracy, and a misclassification of 0.17% on the entire sample space, while C5.0 reported 98.6%, random forest 94.44%, and gradient boosted machine resulted in 95.61% fitting. The variable importance of each primary discriminating attribute is platelet 43%, hemoglobin 24%, white blood cells 4%, and sex of the child 4%. An overall accuracy of 87.4% was recorded for the classifier. Platelet count abnormality can be considered as a major factor in predicting pediatric ALL. The machine learning algorithms can be applied efficiently to provide details for the prognosis for better treatment outcome. Graphical Abstract Identification of significant risks in pediatric acute lymphoblastic leukemia (ALL) through machine learning (ML) approach.

Spatial-Temporal Cluster Analysis of Childhood Cancer in California

BACKGROUND

The observance of nonrandom space-time groupings of childhood cancer has been a concern of health professionals and the general public for decades. Many childhood cancers are suspected to have initiated in utero; therefore, we examined the spatial-temporal randomness of the birthplace of children who later developed cancer.

METHODS

We performed a space-time cluster analysis using birth addresses of 5,896 cases and 23,369 population-based, age-, sex-, and race/ethnicity-matched controls in California from 1997 to 2007, evaluating 20 types of childhood cancer and three a priori designated subgroups of childhood acute lymphoblastic leukemia (ALL). We analyzed data using a newly designed semiparametric analysis program, ClustR, and a common algorithm, SaTScan.

RESULTS

We observed evidence for nonrandom space-time clustering for ALL diagnosed at 2-6 years of age in the South San Francisco Bay Area (ClustR P = 0.04, SaTScan P = 0.07), and malignant gonadal germ cell tumors in a region of Los Angeles (ClustR P = 0.03, SaTScan P = 0.06). ClustR did not identify evidence of clustering for other childhood cancers, although SaTScan suggested some clustering for Hodgkin lymphoma (P = 0.09), astrocytoma (P = 0.06), and retinoblastoma (P = 0.06).

CONCLUSIONS

Our study provides evidence that childhood ALL diagnosed at 2-6 years and malignant gonadal germ cell tumors sporadically occurs in nonrandom space-time clusters. Further research is warranted to identify epidemiologic features that may inform the underlying etiology.

Protecting Children from Toxic Waste: Data-Usability Evaluation Can Deter Flawed Cleanup

Nearly 25 percent of US children live within 2 km of toxic-waste sites, most of which are in urban areas. They face higher rates of cancer than adults, partly because the dominant contaminants at most US hazardous-waste sites include genotoxic carcinogens, like trichloroethylene, that are much more harmful to children. The purpose of this article is to help protect the public, especially children, from these threats and to improve toxics-remediation by beginning to test our hypothesis: If site-remediation assessments fail data-usability evaluation (DUE), they likely compromise later cleanups and public health, especially children’s health. To begin hypothesis-testing, we perform a focused DUE for an unremediated, Pasadena, California toxic site. Our DUE methods are (a) comparing project-specific, remediation-assessment data with the remediation-assessment conceptual site model (CSM), in order to identify data gaps, and (b) using data-gap directionality to assess possible determinate bias (whether reported toxics risks are lower/higher than true values). Our results reveal (1) major CSM data gaps, particularly regarding Pasadena-toxic-site risks to children; (2) determinate bias, namely, risk underestimation; thus (3) likely inadequate remediation. Our discussion shows that if these results are generalizable, requiring routine, independent, DUEs might deter flawed toxic-site assessment/cleanup and resulting health threats, especially to children.

Using routine, independent, scientific-data audits as an early-warning for potentially fraudulent toxic-site cleanup: PCE, TCE, and other VOCs at the former Naval-Ordnance Test Station, Pasadena, California

Two of the most prevalent Superfund-site contaminants are carcinogenic solvents PCE (perchloroethylene) and TCE (trichloroethylene). Because their cleanup is difficult and costly, remediators have repeatedly falsified site-cleanup data, as Tetra Tech apparently did recently in San Francisco. Especially for difficult-to-remediate toxins, this paper hypothesizes that scientific misrepresentations occur in toxic-site assessments, before remediation even begins. To begin to test this hypothesis, the paper (1) defines scientific-data audits (assessing whether published conclusions contradict source data), (2) performs a preliminary scientific-data audit of toxic-site assessments by consultants Ninyo and Moore for developer Trammell Crow. Trammel Crow wants to build 550 apartments on an unremediated Pasadena, California site - once a premier US Navy weapons-testing/development facility. The paper (3) examines four key Ninyo-and-Moore conclusions, that removing only localized metals-hotspots will (3.1) remediate TCE/PCE; (3.2) leave low levels of them; (3.3) clean the northern half of soil, making it usable for grading, and (3.4) ensure site residents have lifetime cancer risks no greater than 1 in 3,000. The paper (4) shows that source data contradict all four conclusions. After summarizing the benefits of routine, independent, scientific-data audits (RISDA), the paper (5) argues that, if these results are generalizable, RISDA might help prevent questionable toxic-site assessments, especially those of expensive-to-remediate toxins like PCE/TCE.

Reconstructing Historical VOC Concentrations in Drinking Water for Epidemiological Studies at a U.S. Military Base: Summary of Results

A U.S. government health agency conducted epidemiological studies to evaluate whether exposures to drinking water contaminated with volatile organic compounds (VOC) at U.S. Marine Corps Base Camp Lejeune, North Carolina, were associated with increased health risks to children and adults. These health studies required knowledge of contaminant concentrations in drinking water—at monthly intervals—delivered to family housing, barracks, and other facilities within the study area. Because concentration data were limited or unavailable during much of the period of contamination (1950s–1985), the historical reconstruction process was used to quantify estimates of monthly mean contaminant-specific concentrations. This paper integrates many efforts, reports, and papers into a synthesis of the overall approach to, and results from, a drinking-water historical reconstruction study. Results show that at the Tarawa Terrace water treatment plant (WTP) reconstructed (simulated) tetrachloroethylene (PCE) concentrations reached a maximum monthly average value of 183 micrograms per liter (μg/L) compared to a one-time maximum measured value of 215 μg/L and exceeded the U.S. Environmental Protection Agency’s current maximum contaminant level (MCL) of 5 μg/L during the period November 1957–February 1987. At the Hadnot Point WTP, reconstructed trichloroethylene (TCE) concentrations reached a maximum monthly average value of 783 μg/L compared to a one-time maximum measured value of 1400 μg/L during the period August 1953–December 1984. The Hadnot Point WTP also provided contaminated drinking water to the Holcomb Boulevard housing area continuously prior to June 1972, when the Holcomb Boulevard WTP came on line (maximum reconstructed TCE concentration of 32 μg/L) and intermittently during the period June 1972–February 1985 (maximum reconstructed TCE concentration of 66 μg/L). Applying the historical reconstruction process to quantify contaminant-specific monthly drinking-water concentrations is advantageous for epidemiological studies when compared to using the classical exposed versus unexposed approach.

Dust metal loadings and the risk of childhood acute lymphoblastic leukemia

We evaluated the relationship between the risk of childhood acute lymphoblastic leukemia (ALL) and the levels of metals in carpet dust. A dust sample was collected from the homes of 142 ALL cases and 187 controls participating in the California Childhood Leukemia Study using a high volume small surface sampler (2001-2006). Samples were analyzed using microwave-assisted acid digestion in combination with inductively coupled plasma mass spectrometry for arsenic, cadmium, chromium, copper, lead, nickel, tin, tungsten, and zinc. Eight metals were detected in at least 85% of the case and control homes; tungsten was detected in <15% of homes. Relationships between dust metal loadings (μg metal per m(2) carpet) and ALL risk were modeled using multivariable logistic regression, adjusting for the child's age, sex, and race/ethnicity and confounders, including household annual income. A doubling of dust metal loadings was not associated with significant changes in ALL risk (odds ratio (95% confidence interval): arsenic: 0.96 (0.86, 1.07), cadmium: 0.92 (0.81, 1.05), chromium: 1.01 (0.90, 1.14), copper: 0.97 (0.91, 1.03), lead: 1.01 (0.93, 1.10), nickel: 0.95 (0.82, 1.09), tin: 0.96 (0.86, 1.08), and zinc: 0.94 (0.84, 1.05)). Our findings do not support the hypothesis that metals in carpet dust are risk factors for childhood ALL.

Developmental Exposure to Environmental Toxicants

Children interact with the physical environment differently than adults, and are uniquely susceptible to environmental toxicants. Routes of absorption, distribution, metabolism, and target organ toxicities vary as children grow and develop. This article summarizes the sources of exposure and known adverse effects of toxicants that are ubiquitous in our environment, including tobacco smoke, ethanol, solvents, heavy metals, volatile organic compounds, persistent organic pollutants, and pesticides. Preventive strategies that may be used in counseling children and their families are highlighted.

Long-term health effects of early life exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study

BACKGROUND

While adult exposure to PCE is known to have toxic effects, there is little information on the long-term impact of prenatal and early childhood exposure. We undertook a retrospective cohort study to examine the effects of their early life exposure to PCE-contaminated drinking water. This retrospective cohort study examined whether prenatal and early childhood exposure to PCE-contaminated drinking water influenced the risk of a variety of chronic conditions among adults who were born between 1969 and 1983 in the Cape Cod area of Massachusetts.

METHODS

Eight hundred and thirty-one participants with prenatal and early childhood PCE exposure and 547 unexposed participants were studied. Individuals completed questionnaires to gather information on demographic characteristics, chronic conditions, and other sources of solvent exposure. The location of residences from birth through 1990 were used to estimate PCE exposure with U.S. EPA's water distribution system modeling software (EPANET) modified to incorporate a leaching and transport model.

RESULTS

No associations were observed between early life PCE exposure and current occurrence of obesity, diabetes, cardiovascular disease, hypertension, color blindness, near- and far sightedness and dry eyes. In contrast, a 1.8-fold increased risk of cancer (95% CI: 0.8, 4.0) was seen among individuals with any early life exposure. These results were based on 31 participants (23 exposed and 8 unexposed) who reported cancers at a variety of anatomical sites, particularly the cervix. A 1.5-fold increase in the risk of epilepsy (95% CI: 0.6, 3.6, based on 16 exposed and 7 unexposed participants) was also observed among individuals with any early life exposure that was further increased to 1.8 (95% CI: 0.7, 4.6) among those with exposure at or above the sample median.

CONCLUSIONS

These results suggest that the risk of epilepsy and certain types of cancer such as cervical cancer may be increased among adults who were exposed to PCE-contaminated drinking water exposure during gestation and early childhood. These findings should be interpreted cautiously because of the study limitations and confirmed in follow-up investigations of similarly exposed populations with medically-confirmed diagnoses. This relatively young study population should also be monitored periodically for subsequent changes in disease risk.

Inflammatory breast cancer clusters: A hypothesis

Cancer clusters have long been a focus of interest because of the possibility of identifying etiologic agents. Only on rare occasions, however, have such cluster investigations been successful. One major difficulty in cluster investigations, particularly in the area of breast cancer, is the long latent period. There have been a number of publications providing a discouraging picture regarding cancer cluster investigations. The possibility of learning from a cluster investigation, however, is greatly increased if the cancer involved is relatively rare and if it has a short latent period. Inflammatory breast cancer (IBC) fits these criteria and is worth pursuing because of the strong evidence that environmental factors play a major role. In this report we describe our experience with several clusters and the lessons learned which are now being utilized to improve investigation of future IBC clusters. The first IBC cluster that we evaluated was in 2000, when we were asked to investigate an apparent cluster of IBC in Castro Valley, California where three women in an office setting of 24 people were diagnosed with IBC in a ten month period from May 1999 to March 2000. Our investigation of this striking cluster did not yield a specific trigger for this cluster but it did indicate that the women involved all had at least two IBC risk factors that may well have made them susceptible to getting IBC. We are now investigating another apparent cluster in Texas and are aware of several others requiring careful consideration. We see a need for a consistent protocol for the evaluation of IBC clusters focusing on the laboratory investigation of environmental triggers, primarily infectious agents and chemical carcinogens.

Cancer cluster investigations: review of the past and proposals for the future

Residential clusters of non-communicable diseases are a source of enduring public concern, and at times, controversy. Many clusters reported to public health agencies by concerned citizens are accompanied by expectations that investigations will uncover a cause of disease. While goals, methods and conclusions of cluster studies are debated in the scientific literature and popular press, investigations of reported residential clusters rarely provide definitive answers about disease etiology. Further, it is inherently difficult to study a cluster for diseases with complex etiology and long latency (e.g., most cancers). Regardless, cluster investigations remain an important function of local, state and federal public health agencies. Challenges limiting the ability of cluster investigations to uncover causes for disease include the need to consider long latency, low statistical power of most analyses, uncertain definitions of cluster boundaries and population of interest, and in- and out-migration. A multi-disciplinary Workshop was held to discuss innovative and/or under-explored approaches to investigate cancer clusters. Several potentially fruitful paths forward are described, including modern methods of reconstructing residential history, improved approaches to analyzing spatial data, improved utilization of electronic data sources, advances using biomarkers of carcinogenesis, novel concepts for grouping cases, investigations of infectious etiology of cancer, and "omics" approaches.

Evaluation of exposure to contaminated drinking water and specific birth defects and childhood cancers at Marine Corps Base Camp Lejeune, North Carolina: a case-control study

BACKGROUND

Drinking water supplies at Marine Corps Base Camp Lejeune were contaminated with trichloroethylene, tetrachloroethylene, benzene, vinyl chloride and trans-1,2-dichloroethylene during 1968 through 1985.

METHODS

We conducted a case control study to determine if children born during 1968-1985 to mothers with residential exposure to contaminated drinking water at Camp Lejeune during pregnancy were more likely to have childhood hematopoietic cancers, neural tube defects (NTDs), or oral clefts. For cancers, exposures during the first year of life were also evaluated. Cases and controls were identified through a survey of parents residing on base during pregnancy and confirmed by medical records. Controls were randomly sampled from surveyed participants who had a live birth without a major birth defect or childhood cancer. Groundwater contaminant fate and transport and distribution system models provided estimates of monthly levels of drinking water contaminants at mothers' residences. Magnitude of odds ratios (ORs) was used to assess associations. Confidence intervals (CIs) were used to indicate precision of ORs. We evaluated parental characteristics and pregnancy history to assess potential confounding.

RESULTS

Confounding was negligible so unadjusted results were presented. For NTDs and average 1st trimester exposures, ORs for any benzene exposure and for trichloroethylene above 5 parts per billion were 4.1 (95% CI: 1.4-12.0) and 2.4 (95% CI: 0.6-9.6), respectively. For trichloroethylene, a monotonic exposure response relationship was observed. For childhood cancers and average 1st trimester exposures, ORs for any tetrachloroethylene exposure and any vinyl chloride exposure were 1.6 (95% CI: 0.5-4.8), and 1.6 (95% CI: 0.5-4.7), respectively. The study found no evidence suggesting any other associations between outcomes and exposures.

CONCLUSION

Although CIs were wide, ORs suggested associations between drinking water contaminants and NTDs. ORs suggested weaker associations with childhood hematopoietic cancers.

The epigenome as a potential mediator of cancer and disease prevention in prenatal development

Epigenetic events establish a particular gene expression signature for each cell type during differentiation and fertilization. Disruption of these epigenetic programs in response to environmental stimuli during prenatal exposure dysregulates the fetal epigenome, potentially impacting susceptibility to disease later in life (the fetal basis of adult disease). Maternal dietary modifications during gestation and lactation play a pivotal role in the period of fetal (re)programming. Recently, many studies have demonstrated the impact of maternal nutrition on the fetal epigenome. This review discusses the complex interplay among various environmental factors and epigenetic mechanisms that have been found to affect offspring in human and animal models. Further, it summarizes the impact of various dietary phytochemicals capable of modulating the epigenome with regard to diverse human cancers and childhood cancer, specifically those with potential environmental etiology through maternal consumption during pregnancy and lactation. Other dietary agents that are still untested as to their effectiveness in transplacental studies are also discussed. The recent developments discussed herein enhance current understanding of how chemopreventive agents act and their potential to impact the prenatal epigenome; they may also aid efforts to identify dietary interventions that can be beneficial in treating and preventing disease.

Cancer clusters in the USA: what do the last twenty years of state and federal investigations tell us?

Background

Cancer clusters garner considerable public and legislative attention, and there is often an expectation that cluster investigations in a community will reveal a causal link to an environmental exposure. At a 1989 national conference on disease clusters, it was reported that cluster studies conducted in the 1970s and 1980s rarely, if ever, produced important findings. We seek to answer the question: Have cancer cluster investigations conducted by US health agencies in the past 20 years improved our understanding of cancer etiology, or informed cancer prevention and control?

Methods

We reviewed publicly available cancer cluster investigation reports since 1990, obtained from literature searches and by canvassing all 50 states and the District of Columbia. Investigations were categorized with respect to cancer type(s), hypothesized exposure, whether perceived clusters were confirmed (e.g. by elevated incidence), and conclusions about a link between cancer(s) of concern and hypothesized environmental exposure(s).

Results

We reviewed 428 investigations evaluating 567 cancers of concern. An increase in incidence was confirmed for 72 (13%) cancer categories (including the category “all sites”). Three of those were linked (with variable degree of certainty) to hypothesized exposures, but only one investigation revealed a clear cause.

Conclusions

It is fair to state that extensive efforts to find causes of community cancer clusters have not been successful. There are fundamental shortcomings to our current methods of investigating community cancer clusters. We recommend a multidisciplinary national dialogue on creative, innovative approaches to understanding when and why cancer and other chronic diseases cluster in space and time.

Maternal alcohol consumption during pregnancy and risk of childhood leukemia: systematic review and meta-analysis

BACKGROUND

Leukemia is the most frequently occurring cancer in children. Although its etiology is largely unknown, leukemia is believed to result from an interaction between genetic and environmental factors. Among different potential risk factors, the possible role of maternal alcohol consumption during pregnancy has been questioned.

METHODS

To assess the association between maternal alcohol consumption during pregnancy and childhood leukemia, a systematic review and meta-analysis of published studies was done.

RESULTS

Twenty-one case-control studies were included in categorical and dose-response meta-analyses. No cohort study was identified. Analyses were conducted by type of leukemia, children's age at diagnosis, and type of alcoholic beverage and trimester of pregnancy at alcohol use. Alcohol intake during pregnancy (yes versus no) was statistically significantly associated with childhood acute myeloid leukemia (AML) [odds ratio (OR), 1.56; 95% confidence interval (CI), 1.13-2.15] but not with acute lymphoblastic leukemia (OR, 1.10; 95% CI, 0.93-1.29). Heterogeneity between studies was observed. The OR of AML for an increase of a drink per week was 1.24 (95% CI, 0.94-1.64). The association of alcohol intake during pregnancy with AML was observed for cancers diagnosed at age 0 to 4 years (OR, 2.68; 95% CI, 1.85-3.89) in five studies without heterogeneity (I2<or=0.1%).

CONCLUSIONS

The results of case-control studies indicate that maternal alcohol consumption during pregnancy is associated with a significantly increased risk of AML in young children.

IMPACT

Avoidance of maternal alcohol drinking during pregnancy might contribute to a decrease in the risk of childhood AML.

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.

Aetiology of childhood leukaemia

The acute leukaemias account for about 30% of all malignancy seen in childhood across the Western world. A peak incidence of precursor B cell ALL has emerged as socio-economic conditions have improved in countries worldwide. From twin studies and the use of neonatal blood spots it has been possible to back track the first initiating genetic events within critical haemopoietic cells to foetal development in utero for most precursor B cell ALL and some cases of AML. These events may occur as part of normal foetal development. Whether other factors (environmental or constitutional) are involved to increase the chance of these first genetic changes happening is unclear. For some leukaemias (e.g. infant MLL positive ALL) the first event appears adequate to create a malignant clone but for the majority of ALL and AML further 'genetic' changes are required, probably postnatal. Many environmental factors have been proposed as causative for leukaemia but only ionising irradiation and certain chemicals, e.g. benzene and cytotoxics (alkylators and topoisomerase II inhibitors) have been confirmed and then principally for acute myeloid leukaemia. It appears increasingly likely that delayed, dysregulated responses to 'common' infectious agents play a major part in the conversion of pre-leukaemic clones into overt precursor B cell ALL, the most common form of childhood leukaemia. Constitutional polymorphic alleleic variants in immune response genes (especially the HLA Class II proteins) and cytokines may play a role in determining the type of immune response. High penetrance germ-line mutations are involved in only about 5% of childhood leukaemias (more in AML than ALL). There is little evidence to support any role of viral transformation in causation, unlike in animals. Other environmental factors for which some evidence exists include non-ionising electromagnetic radiation and electric fields, although their mode of action in leukaemogenesis remains unclear. There is no single cause for childhood leukaemia and for most individuals a combination of factors appears to be necessary; all involving gene-environment interactions. To date few clear preventative measures have emerged, except the complete avoidance of first trimester X-rays in pregnancy; a healthy diet with adequate oral folic acid intake both preconception and early in pregnancy; and the early exposure of children to other children outside the home to facilitate stimulation and maturation of the natural immune system. Here then are clear echoes of the "hygiene hypothesis" regarding the initiation of allergies, autoimmune disease and type I diabetes mellitus in children and young people.

Superfund: is it safe to go home?

The Superfund law does not effectively address exposure of the residents surrounding a hazardous waste site before, during, and after cleanup.

Environmental factors and childhood acute leukemias and lymphomas

This review considers recent studies regarding the role of environmental factors in the etiology of childhood leukemia and lymphoma. Potential environmental risk factors identified for childhood leukemia include exposure to magnetic fields of more than 0.4 micro Tessla, exposure to pesticides, solvents, benzene and other hydrocarbons, maternal alcohol consumption (but only for certain genotypes), contaminated drinking water, infections, and high birth weight. The finding of space-time clustering and seasonal variation also supports a role for infections. There is little evidence linking childhood leukemia with lifetime exposure to ionizing radiation although fetal exposures to X-rays are associated with increased risk. Breast-feeding, consumption of fresh fruit and vegetables and having allergies all appear to be protective. Burkitt lymphoma (BL) is confined to areas of the world where malaria is endemic, with the additional involvement of the Epstein-Barr virus (EBV) as a co-factor. Environmental risk factors suggested for other types of non-Hodgkin lymphoma (NHL) include exposure to ionizing radiation (both lifetime and antenatal), pesticides, and, in utero exposure to cigarette smoke, benzene and nitrogen dioxide (via the mother). Hodgkin lymphoma (HL) is especially associated with higher levels of socioeconomic deprivation, but breast-feeding seems to confer lower risk. This is consistent with an infection or immune-response mediated etiology for HL.

Design issues in small-area studies of environment and health

BACKGROUND

Small-area studies are part of the tradition of spatial epidemiology, which is concerned with the analysis of geographic patterns of disease with respect to environmental, demographic, socioeconomic, and other factors. We focus on etiologic research, where the aim is to make inferences about spatially varying environmental factors influencing the risk of disease.

METHODS AND RESULTS

We illustrate the approach through three exemplars: a) magnetic fields from overhead electric power lines and the occurrence of childhood leukemia, which illustrates the use of geographic information systems to focus on areas with high exposure prevalence; b) drinking-water disinfection by-products and reproductive outcomes, taking advantage of large between- to within-area variability in exposures from the water supply; and c) chronic exposure to air pollutants and cardiorespiratory health, where issues of socioeconomic confounding are particularly important.

DISCUSSION

The small-area epidemiologic approach assigns exposure estimates to individuals based on location of residence or other geographic variables such as workplace or school. In this way, large populations can be studied, increasing the ability to investigate rare exposures or rare diseases. The approach is most effective when there is well-defined exposure variation across geographic units, limited within-area variation, and good control for potential confounding across areas.

CONCLUSIONS

In conjunction with traditional individual-based approaches, small-area studies offer a valuable addition to the armamentarium of the environmental epidemiologist. Modeling of exposure patterns coupled with collection of individual-level data on subsamples of the population should lead to improved risk estimates (i.e., less potential for bias) and help strengthen etiologic inference.

Uses of and exposure to trichloroethylene in U.S. industry: a systematic literature review

This article describes a systematic review of the industrial hygiene literature for uses of trichloroethylene (TCE) in industry for the exposure assessment of two population-based case control studies of brain cancer in the United States. Papers and reports that address uses of and exposures to TCE were identified from MEDLINE, TOXLINE, NIOSHTIC, the NIOSH Health Hazard Evaluation database (keywords: chlorinated solvents and trichloroethylene), and in other reviews. This search was complemented by reviewing the reference lists from the identified literature. The collected information was systematized by the Standard Industrial Classification (SIC) system, and measurement data reported in the literature were summarized in a database. TCE use was extensive from the early 1920s through the 1970s mainly as a degreasing agent in metal-fabricating operations. After the 1970s it became less popular because of environmental concerns. TCE historically has had a multitude of uses in many other industries, e.g., dry cleaning, textile, electronics, leather, and rubber. Also, many products like adhesives, drugs, paints, inks, and various industrial products have contained TCE. It was banned as a food additive and in cosmetics in 1977. The arithmetic mean (AM) of the measurements across all industries and decades was 38.2 ppm. The highest personal and area air levels were reported in vapor degreasing (AM of 44.6 ppm). Most TCE measurements were performed in the 1950s, 1970s, and 1980s. The data described here could be used by exposure assessors as is to identify the presence and approximate levels of exposure. Using the same information as a basis should increase the reliability of the assessments, making it easier to compare both the exposure assessment methods and the epidemiologic results across different studies.

Population-based retrieval of newborn dried blood spots for researching paediatric cancer susceptibility genes

We have demonstrated the feasibility of linking newborn blood spots, population-based cancer incidence data and birth certificate data. Incident cases of acute lymphocytic leukaemia and population-based controls were ascertained. We retrieved dried blood spot specimens, isolated and amplified DNA, and assayed the cancer susceptibility genes GSTT1 and GSTM1. The double null genotype was over-represented in the cases, consistent with previous reports based on other epidemiological methods. The design avoids issues of participation bias by cases and controls and can be used to investigate interactions of susceptibility genes and xenobiotics in semi-ecological studies. It can be useful for generating or testing hypotheses on associations of other paediatric illness and environmental contaminants.

Trichloroethylene cancer epidemiology: a consideration of select issues

A large body of epidemiologic evidence exists for exploring causal associations between cancer and trichloroethylene (TCE) exposure. The U.S. Environmental Protection Agency 2001 draft TCE health risk assessment concluded that epidemiologic studies, on the whole, support associations between TCE exposure and excess risk of kidney cancer, liver cancer, and lymphomas, and, to a lesser extent, cervical cancer and prostate cancer. As part of a mini-monograph on key issues in the health risk assessment of TCE, this article reviews recently published scientific literature examining cancer and TCE exposure and identifies four issues that are key to interpreting the larger body of epidemiologic evidence: a) relative sensitivity of cancer incidence and mortality data ; b) different classifications of lymphomas, including non-Hodgkin lymphoma ; c) differences in data and methods for assigning TCE exposure status ; and d) different methods employed for causal inferences, including statistical or meta-analysis approaches. The recent epidemiologic studies substantially expand the epidemiologic database, with seven new studies available on kidney cancer and somewhat fewer studies available that examine possible associations at other sites. Overall, recently published studies appear to provide further support for the kidney, liver, and lymphatic systems as targets of TCE toxicity, suggesting, as do previous studies, modestly elevated (typically 1.5-2.0) site-specific relative risks, given exposure conditions in these studies. However, a number of challenging issues need to be considered before drawing causal conclusions about TCE exposure and cancer from these data.

A meta-analysis of occupational trichloroethylene exposure and multiple myeloma or leukaemia

BACKGROUND

Trichloroethylene (TCE) has been widely used as an industrial solvent and degreasing agent.

AIMS

We conducted a meta-analysis of epidemiologic studies of occupational TCE exposure and multiple myeloma (MM) or leukaemia.

METHODS

We identified a total of eight cohort or case-control studies that enumerated a TCE-exposed study population and presented relative risk (RR) estimates for MM (n = 7) and/or leukaemia (n = 7). The individual studies included aerospace or aircraft workers (n = 3 studies), workers from a transformer manufacturing plant (n = 1 study) and workers from numerous occupations who, based on biomonitoring or extensive industrial hygiene exposure measurements, were likely exposed to TCE (n = 4). We used random effects models to calculate summary relative risk estimates (SRRE). In addition, we examined heterogeneity across studies and the relative influence of each individual study on the overall meta-analysis.

RESULTS

No association was observed for MM (SRRE = 1.05, 95% CI: 0.80-1.38; P value for heterogeneity = 0.94) or leukaemia (SRRE = 1.11, 95% CI: 0.93-1.32; P value for heterogeneity = 0.50), based on TCE-exposed subgroup meta-analyses. Study-specific RR estimates for MM ranged between 0.57 and 1.62. RRs for leukaemia ranged between 1.05 and 1.15 in five studies, while one study reported a 2-fold increased RR and another study reported an inverse association of 0.60. All confidence intervals (CIs) for study-specific estimates included 1.0.

CONCLUSIONS

The results of this meta-analysis do not support an etiologic association between occupational TCE exposure and risk of MM or leukaemia.

Exposure assessment in investigations of waterborne illness: a quantitative estimate of measurement error

Background

Exposure assessment is typically the greatest weakness of epidemiologic studies of disinfection by-products (DBPs) in drinking water, which largely stems from the difficulty in obtaining accurate data on individual-level water consumption patterns and activity. Thus, surrogate measures for such waterborne exposures are commonly used. Little attention however, has been directed towards formal validation of these measures.

Methods

We conducted a study in the City of Hamilton, Ontario (Canada) in 2001–2002, to assess the accuracy of two surrogate measures of home water source: (a) urban/rural status as assigned using residential postal codes, and (b) mapping of residential postal codes to municipal water systems within a Geographic Information System (GIS). We then assessed the accuracy of a commonly-used surrogate measure of an individual's actual drinking water source, namely, their home water source.

Results

The surrogates for home water source provided good classification of residents served by municipal water systems (approximately 98% predictive value), but did not perform well in classifying those served by private water systems (average: 63.5% predictive value). More importantly, we found that home water source was a poor surrogate measure of the individuals' actual drinking water source(s), being associated with high misclassification errors.

Conclusion

This study demonstrated substantial misclassification errors associated with a surrogate measure commonly used in studies of drinking water disinfection byproducts. Further, the limited accuracy of two surrogate measures of an individual's home water source heeds caution in their use in exposure classification methodology. While these surrogates are inexpensive and convenient, they should not be substituted for direct collection of accurate data pertaining to the subjects' waterborne disease exposure. In instances where such surrogates must be used, estimation of the misclassification and its subsequent effects are recommended for the interpretation and communication of results. Our results also lend support for further investigation into the quantification of the exposure misclassification associated with these surrogate measures, which would provide useful estimates for consideration in interpretation of waterborne disease studies.

Public health partnerships addressing childhood cancer investigations: case study of Toms River, Dover Township, New Jersey, USA

Toms River, located in Dover Township, Ocean County, New Jersey, USA, experienced an increased incidence in childhood leukemia, brain, and central nervous system cancers from the mid-1980s through the early 1990s. These findings initiated a series of community-based activities that lead to the establishment of a successful partnership between the community, public health, and environmental agencies. The common goal of this partnership was to investigate linkages between environmental exposures and childhood cancers. The investigation was comprehensive in nature and a product of an extensive collaborative effort on the part of community, local, state, and federal health agencies, and university research organizations. Central to the success of this partnership was development of a public health response plan. This response plan served to coordinate activities of various entities and ensure that actions to cease or reduce ongoing exposures were implemented in addressing the incidence of childhood cancers using the partnership paradigm. The authors propose six rules of engagement: (1) seek out willing participants, (2) establish an equitable partnership, (3) consider each partner's perspective, (4) define goals and roles for each partner, (5) seek out innovative opportunities, and (6) assure scientific credibility. The application of these rules of engagement led to innovations and advances in the fields of environmental health science and public health practice.

Cancer Cluster Investigations

A rural community expressed concern about a perceived excess of kidney and pancreatic cancer coupled with contamination of drinking water with atrazine, benzene, ethylene dibromide, and nitrate. Incidence and mortality for these two cancers were compared to what might be expected. A literature review was conducted for risk factors for kidney and pancreatic cancer as well as for the effects of the above 4 chemicals on these 2 cancers. Interviews with cases or surrogates ascertained chemical and risk factor exposures for these 2 cancers. Chemical exposures found in the public drinking water supply were evaluated as to their carcinogenicity. Hospital cases were compared to cases in the cancer registry. No statistically significant increases in kidney and pancreatic cancer incidence or mortality were found. The major risk factor found in the literature for these 2 cancers was smoking. Most of the cases were smokers and the chemicals found in the drinking water were not found to pose a risk for these 2 cancers. This approach provided considerable information, suggested prevention options and additional research, and is recommended for responding to cancer cluster concerns originating in the community (reactive approach). A proactive approach to cancer cluster surveillance and research was also used and is recommended for state or large local health departments.