Christopher T. De Rosa

Public Health Implications of Persistent Toxic Substances in the Great Lakes and St. Lawrence Basins

This paper summarizes the primary literature and reviews research findings of the health implications associated with exposure to persistent toxic substances (PTSs) in the Great Lakes and St. Lawrence River basins. Most of these studies focus on fish consumption because this route has been shown to be the major route of exposure to PTSs; however, other exposure routes including air, diet, and water are also important. n nRecent studies complement and build upon the epidemiologic, wildlife, and laboratory data gathered over the last three decades documenting health consequences associated with PTSs. For example, findings in the United States (U.S.) indicate that at-risk populations, e.g., certain ethnic groups, sport anglers, the elderly, pregnant women, children, fetuses, and nursing infants, continue to be exposed to PTSs including PCBs, dioxins, chlorinated pesticides, and mercury. Designating these particular populations as “at-risk” is not meant to suggest that other populations with lower exposures, body burdens, or susceptibilities are not without risk. The human health data for these groups indicate that: (1) reproductive function may be disrupted by exposure to PCBs and other PTSs; (2) neurobehavioral and developmental deficits occur in newborns and continue through school-age children from in utero exposure to PCBs and other PTSs; and (3) other systemic effects, e.g., self-reported liver disease and diabetes, may be associated with elevated serum levels of PCBs. n nFurther research is needed to extend the information available to assess and understand the etiology of these health findings. Other conclusions include: (1) the benefits from fish consumption should be considered when evaluating health implications offish consumption; (2) health education is especially valuable in mitigating potential effects and informing individuals about certain windows of vulnerability, e.g., pregnancy; and (3) pollution prevention strategies remain a key to reducing toxic chemical loading.

ATSDR Evaluation of Health Effects of Chemicals. V. Xylenes: Health Effects, Toxicokinetics, Human Exposure, and Environmental Fate

Xylenes, or dimethylbenzenes, are among the highest-volume chemicals in production. Common uses are for gasoline blending, as a solvent or component in a wide variety of products from paints to printing ink, and in the production of phthalates and polyester. They are often encountered as a mixture of the three dimethyl isomers, together with ethylbenzene. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that are of greatest concern for public health purposes. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of the bulk of this profile (ATSDR, 1995) into the mainstream scientific literature. An extensive listing of known human and animal health effects, organized by route, duration, and end point, is presented. Toxicological information on toxicokinetics, biomarkers, interactions, sensitive subpopulations, reducing toxicity after exposure, and relevance to public health is also included. Environmental information encompasses physical properties, production and use, environmental fate, levels seen in the environment, analytical methods, and a listing of regulations. ATSDR, as mandated by CERCLA (or Superfund), prepares these profiles to inform and assist the public.

The Role of Exposure Versus Body Burden Data in Deriving Health Guidance Values

The Agency for Toxic Substances and Disease Registry (ATSDR) derives health-based guidance values to estimate daily human exposure to hazardous substances that are likely to be without appreciable risk of adverse noncancer effects for specific routes and durations of exposure. Most of these guidance values are derived from data showing external dose/health effect relationships. However, for chemicals that persist in the body, information on body burdens may provide more accurate understanding of their toxicity. This article evaluates the exposure versus body burden approaches using 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and lead as examples.

Findings and accomplishments of ATSDR's Superfund-mandated Substance-Specific Applied Research Program

Priority research needs determined by the Agency for Toxic Substances and Disease Registry (ATSDR) for the agencies top-ranked hazardous substances are being filled via regulatory mechanisms, private sector voluntarism, and university-based research. To date, 17 studies have been completed, 12 are ongoing, and 12 are currently planned. Under the direction of the Substance-Specific Applied Research Program (SSARP), ATSDR-supported research has filled research needs that significantly improved the information base available for making appropriate public health decisions. With the knowledge and understanding gained from this research, health professionals are better able to identify and interdict significant exposure and mitigate toxicity when exposure occurs. Thus, the SSARP has played, and continues to play, a vital role in contributing towards improving ATSDRs efforts to meet its mission and goals in environmental public health. In addition to addressing research needs of interest to ATSDR, findings from the program have contributed to the overall scientific knowledge about the effects of toxic substances in the environment.

Trichloroethylene in the Environment: Public Health Concerns

The Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxi-cological profiles for hazardous substances found at waste sites and elsewhere in the environment. In 1997 the agency updated its toxicological profile for trichloroethylene and included new and expanded information on the health effects associated with exposures to trichloroethylene. Several endpoints of concern are described in the profile. However, in this paper only results from studies reporting developmental and carcinogenic effects from trichloroethylene exposures in human and experimental animal studies are summarized and evaluated. Based on its assessment of the available studies and limitations in the reported findings, ATSDR has determined there is limited but suggestive evidence that developmental effects may be a concern for some persons exposed to TCE in drinking water. Moreover, developmental effects may be the most sensitive of all non-cancer health effects associated with trichloroethylene exposures. Significant questions remain about the likely mode(s) of action for TCE-induced carcinogenesis in humans and the basis for differences in pharmacokinetics handling of TCE across animal strains and sex. However, on the basis of animal data and the suggestive, yet inconclusive, human data available, ATSDR has determined that cancer should be an effect of concern for people exposed to TCE in the environment. ATSDR agrees that the available literature supports the premise that TCE is “reasonably anticipated to be a human carcinogen” as defined by the U.S. National Toxicology Program.

Sentinel Human Health Indicators: A Model for Assessing Human Health Status of Vulnerable Communities

The presence of toxic substances in the Great Lakes (GL) continues to be a significant concern. Eleven of the most persistent and ubiquitous substances were identified as “critical Great Lakes pollutants” by the International Joint Commission (IJC). In some areas of the GL these toxic substances bioaccumulate in sediment and organisms, biomagnify in food webs, and persist at high levels. The Agency for Toxic Substances and Disease Registry (ATSDR) Great Lakes Human Health Effects Research Program (GLHHERP) characterizes contaminant exposures via GL fish consumption and investigates the potential for short- and long-term adverse health effects. The program has identified a set of eight indicators to determine risk. The GLHHERP findings indicate: (1) vulnerable populations are still being exposed to persistent toxic substances (2) body burden levels are two to four times higher than in the general U.S. population, (3) women and minorities are less knowledgeable about fish advisories than other segments of the population, (4) the presence of neurodevelopmental deficits in newborns, and cognitive deficits in children and adults, and (5) disturbances in reproductive parameters have been demonstrated in adults. The public health implications of these findings and the need for intervention strategies are discussed.

Reducing uncertainty in the derivation and application of health guidance values in public health practice. Dioxin as a case study.

Abstract: We were requested by the U.S. Environmental Protection Agency (EPA) to clarify the relationships among the minimal risk level (MRL), action level, and environmental media evaluation guide (EMEG) for dioxin established by the Agency for Toxic Substances and Disease Registry (ATSDR). In response we developed a document entitled “Dioxin and Dioxin‐Like Compounds in Soil, Part I: ATSDR Interim Policy Guideline”; and a supporting document entitled “Dioxin and Dioxin‐Like Compounds in Soil, Part II: Technical Support Document”. In these documents, we evaluated the key assumptions underlying the development and use of the ATSDR action level, MRL, and EMEG for dioxin. We described the chronology of events outlining these different health guidance values for dioxin and identified the areas of uncertainty surrounding these values. Four scientific assumptions were found to have had a great impact on this process; these were: (1) the specific uncertainty factors used, (2) the toxicity equivalent (TEQ) approach, (3) the fractional exposure from different pathways, and (4) the use of body burdens in the absence of exposure data. This information was subsequently used to develop a framework for reducing the uncertainties in public health risk assessment associated with exposure to other chemical contaminants in the environment. Within this framework are a number of future directions for reducing uncertainty, including physiologically based pharmacokinetic modeling (PBPK), benchmark dose modeling (BMD), functional toxicology, and the assessment of chemical mixture interactions.

Great lakes research--important human health findings and their impact on ATSDR's Superfund research program.

The Agency for Toxic Substances and Disease Registry (ATSDR) was created by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, commonly known as Superfund. ATSDR is the principal United States federal public health agency involved with issues of public health and applied science concerning the human health impact of living in the vicinity of a hazardous waste site, or emergencies resulting from unplanned releases of hazardous substances into community environments. In pursuing these mandates, ATSDRs mission is to prevent exposure and adverse human health effects and diminished quality of life associated with exposure to hazardous substances from waste sites, unplanned releases, and other sources of pollution present in the environment. There are more than 2,000 toxic substances found at hazardous waste sites in the United States. ATSDR has developed a prioritized list of 275 substances that pose the greatest hazard to human health. In conducting its work ATSDR has identified data gaps in knowledge about the toxicity of various hazardous substances as well as gaps in human exposure characterization. As part of its mandate, ATSDR initiated a Substance-Specific Applied Research Program (SSARP) to address these data gaps. The ATSDR Great Lakes Human Health Effects Research Program (GLHHERP) is a congressionally-mandated research program that characterizes exposure to persistent toxic substances and investigates the potential for adverse health outcome in at-risk populations. The research findings from this program in the areas of exposure, sociodemographic data, and health effects have significant public health implications for ATSDRs Superfund research activities.

The USEPA and the Toxic Substances Control Act (TSCA) of 1976: The Promise, the Reality, and the Reason(s) Why

As we commemorate the 40th anniversary of the establishment of the U.S. Environmental Protection Agency (EPA), it is appropriate to recognize the many successes of that agency and some of its unrealized expectations. It seems to me that the successes are numerous, for example, EPA’s administration of the Clean Air Act and the Clean Water Act has led to measurable improvements in the nation’s air and water quality. This is not to say that further improvements are not needed, but rather that considerable progress has been made. These kinds of environmental and public health successes are linked to the quality of the statutes that EPA is tasked with enforcing. Good legislation has generally translated into good environmental programs and successful management of environmental hazards. However, where the enabling legislation is weak, EPA’s ability to manage specified environmental hazards is challenged. Such is the case with the Toxic Substances Control Act (TSCA). This editorial will provide some insight into what went wrong with TSCA. This editorial reflects my experience of a former EPA employee who was a member of the working group charged with EPA’s efforts leading to the ban on polychlorinated biphenyls (PCBs). During the 30 years since that time I have been continually engaged with EPA and others in the proposed development of test rules to fill critical data gaps in our knowledge upon which to base chemical safety assessments on behalf of EPA, the Agency for Toxic Substance and Disease Registry (ATSDR), and others. Humankind’s relationship with the environment has been a dichotomous saga of dependence and exploitation. In the early seventies, the burning of the Cuyahoga River in northeast Ohio (Silbergeld and Graham 2008), along with the debacle of Love Canal in New York State, galvanized the political will of the United States, culminating in Earth Day, and the creation of the U.S. Environmental Protection Agency (EPA) in 1970. Since that time, a wide array of environmental legislative mandates, including the National Environmental Policy Act (NEPA 1970), have been enacted. This Act has been characterized as a citizens’ “Bill of Rights,” to clean air, water, and food; which should apply to all citizens of the global community.