Chemical mixtures and health effects at Superfund sites

Risk communication of endocrine-disrupting chemicals: improving knowledge translation and transfer

Public perception of the negative effects of endocrine-disrupting chemicals appears to be higher compared to other chemical pollutants, due to (1) chronic, low-probability effects, and (2) uncertainties about which biological effects may be relevant for human health. Individuals, both expert and lay public, require credible, trustworthy, and understandable information about the scientific evidence of endocrine-disrupting chemicals in order to make informed risk decisions. The creation of a dedicated web site, http://www.emcom.ca, as a tool for knowledge translation and transfer provides the general public with access to scientific experts and bridges the gap between experts and nonexperts through a two-way, interactive communications approach. By obtaining accurate and credible information, individuals can make better-informed decisions concerning endocrine-disrupting chemicals.

Neurobehavioral evaluations of mixtures of trichloroethylene, heptachlor, and di(2-ethylhexyl)phthalate in a full-factorial design

One approach to the toxicological evaluation of chemical mixtures is to construct full dose-response curves for each compound in the presence of a range of doses of each of the other compounds, i.e., a factorial design. This study was undertaken as part of an interdisciplinary project to evaluate a mixture of three environmental pollutants. A full-factorial design was undertaken to determine the neurobehavioral consequences of short-term repeated exposure to five dose levels each of three chemicals, in order to characterize potential two- and three-way interactions. Adult female F344 rats received (p.o.) for 10 days either one of five doses of trichloroethylene, di(2-ethylhexyl)phthalate, or heptachlor, or else one of all possible chemical combinations. Neurobehavioral evaluations were conducted using motor activity and an abbreviated functional observational battery. Response-surface analysis was applied to each of the endpoints. Hypotheses were tested based on the estimated model parameters; of primary interest was the overall test for interaction among the three chemicals. In addition, an abbreviated design was created by fitting only a subset of the data to the model. In general, significant overall interactions that deviated from response additivity were detected for most endpoints (11 of 14). All of the interactions on the neurobehavioral endpoints showed either antagonism, or else an interaction that could not be fully characterized. Often the results of the abbreviated dataset analysis were not the same as for the full-factorial design. This study was extremely intensive, in terms of the number of rats and time required for conduct of the study as well as the data analysis. These results underscore the need for more economical approaches to evaluate the toxic effects of mixtures of chemicals.

Superfund research program--accomplishments and future opportunities

This special issue of the International Journal of Hygiene and Environmental Health provides extensive background on the Superfund programs, findings of specific research studies and future directions. Three federal agencies are leading the effort in this program. They are the National Institute of Environmental Health Sciences, U.S. Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry. As a result of their collaboration, a comprehensive program has been developed that ranges from basic to applied research with the aim of improving public health services and protection. This paper highlights the research within areas of toxicological investigation, exposure assessment, risk evaluation and engaging communities. Each of the agencies has developed strategies and initiatives to enhance the effectiveness of the Superfund research program. The continuation of research will contribute significantly towards achieving the Healthy People 2010 goals that have been set for the United States.