Paul A. Stehr-Green

Human exposure to polychlorinated biphenyls at toxic waste sites: investigations in the United States.

Beginning in 1982, environmental and population data were evaluated from waste sites contaminated with polychlorinated biphenyls (PCBs). Pilot exposure assessment studies were conducted at 12 sites where risks of human exposure were thought to be greatest. Serum PCB levels in persons at highest risk of nonoccupationally related exposures (because of their self-reported frequencies and types of activities in contaminated areas) at 10 sites were within background ranges, even though environmental contamination levels as high as 2.5 parts per billion (ppb) in monitoring well water samples and 330,000 ppb in soil samples were measured. At the 2 remaining sites, elevated serum levels were found in these high-risk persons, which require further evaluation by community surveys. These results illustrate that, despite elevated environmental contaminant levels, unless uptake of chemicals above background exposure levels can be demonstrated, adverse health effects cannot be attributed to waste site chemicals. However, health risks due to background exposure levels, as well as in populations with elevated PCB body burdens need further study.

A Pilot Study of Serum Polychlorinated Biphenyl Levels in Persons at High Risk of Exposure in Residential and Occupational Environments

A pilot study was conducted to determine whether persons at high risk of exposure to three waste sites in the area of Bloomington, Indiana, have abnormally elevated serum polychlorinated biphenyl (PCB) levels. In addition, we attempted to determine which environmental pathways might have contributed most to these exposures. First, a screening questionnaire survey of 995 individuals was conducted; on the basis of these data, 114 of the persons who had the greatest potential for exposure were selected for inclusion in this pilot exposure assessment study. People near these waste sites have higher average serum PCB levels, and a greater percentage have abnormally elevated serum PCB levels, compared with previously characterized populations in the United States. However, we could not distinguish specific pathways of exposure and uptake, with the exception of persons with occupational exposures and, possibly, among persons who reportedly salvaged metal from discarded electrical equipment. Exposures in this community require further evaluation.

An Overview of the Missouri Dioxin Studies

Among the problems inherent in evaluating public health impacts around toxic waste sites are the difficulties in measuring exposure, our incomplete understanding of low-dose effects, the low frequency of disease incidence, the long latency period and silent course of disease development, the nonspecificity of clinical findings, and the probable multifactorial nature of diseases of interest. A multiphase approach for implementing epidemiologic studies in such settings was used in assessing the 2,3,7,8-tetrachlorodibenzodioxin (TCDD, or dioxin) contaminations in Missouri, where waste oil mixtures contaminated with dioxins were sprayed on various sites throughout the state for dust control in 1971. Although the toxic effects of dioxin have been studied extensively in animals and documented in cases of accidental high-level exposure in humans, very little is known of the human health effects, if any, produced by long-term exposure to relatively low levels of dioxin. In addition to medical epidemiologic studies, which were done to evaluate the types of problems present in groups of individuals with high-risk of environmental dioxin exposure, other studies to characterize dioxin levels in adipose tissue and serum are under way in a sample of potentially exposed (as well as in unexposed) Missouri residents. Research in these areas will continue to be pursued to develop a more complete understanding of the risks and appropriate public health interventions in situations of community exposure to environmental dioxins and other environmental contaminants.