ABSTRACT
Chlorinated dibenzo-p-dioxins (CDDs), hexachlorobenzene, dichlorodiphenyl dichloroethane (p,p'-DDE), methylmercury, and polychlorinated biphenyls (PCBs) were selected as an important subset of persistent chemicals detected in breast milk for the purpose of reviewing data on their joint toxic actions following oral exposure. Epidemiological studies of possible health hazards associated with exposure to biopersistent chemicals in breast milk identify mild neurodevelopmental deficits as a possible health hazard. However, the studies did not analyze all the components of the above defined mixture, and, therefore, they are not directly useful for the purposes of conducting exposure-based assessments of hazards associated with this mixture. For this purpose, component-based methodology such as binary weight-of-evidence, the hazard index (HI) and the target-organ toxicity dose (TTD) approaches are recommended. Weight-of-evidence evaluation of the limited animal studies' data on interactions among CDDs, hexachlorobenzene, p,p-DDE, methylmercury, and PCBs indicates that the data are inadequate to warrant a concern for deviations from the additivity assumption. Further, exposure-based health assessments are used, in conjunction with evaluation of community-specific health outcome data, consideration of community health concerns, and biomedical judgement, to assess the degree of public health hazard presented by mixtures of substances released into the environment.
