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.