The impact of PCBs and dioxins on children's health: immunological considerations.

Environmental contaminants include the potentially toxic metals lead, cadmium and mercury; the chlorinated pesticides mirex, toxaphene and hexachlorobenzene; chlorinated dioxins and furans; polyaromatic hydrocarbons; and polychlorinated biphenyls. While many of these chemicals are resistant to degradation in the natural environment, they dissolve readily in oils and thus accumulate in the fatty tissues of fish, birds and mammals. Human exposure is predominantly through the ingestion of contaminated food. An array of toxic effects including effects on the immune system have been described in experimental animals and in humans accidentally exposed to these chemicals. Such studies suggest that the immune system of the developing fetus and the newborn is particularly vulnerable to the toxic effects of chemicals. To fully appreciate the magnitude of risk these chemicals pose to children's health, there is a need for additional carefully focussed epidemiologic and mechanistic studies.