Human health and chemical mixtures: An overview

Unlike laboratory animals, people are rarely exposed to a single hazardous chemical. However, most of the information documenting adverse human health effects from environmental and occupational contaminants has come from stu dies focused on exposure to single chemicals, and there is little informati on available on how two or more contaminants affect humans. Most informatio n on the effects of mixtures comes from animal systems and limited investig ations of isolated human cells in culture, even though the study of mixture s in such systems has also been neglected. Two or more compounds may show a dditive, antagonistic, or synergistic interactions or may act on totally di fferent systems and thus not interact. Furthermore. even a single chemical may have multiple effects and affect more than one organ system. Effects ma y vary with age, and metabolites may have totally different actions from th e parent compound. This paper will review the variety of health effects in humans that may result from environmental contaminants and discuss how such contaminants may interact with each other. We will also present examples o n how different contaminants interact from toxicologic studies of polychlor inated biphenyls performed as part of our Albany, New York, Superfund Basic Research Program project.