How can data on individual DBPs be used to characterize cancer risks posed by chemical mixtures?
Andersen: Several strategies are possible. In general, they involve reconstituting a representative mixture, as found in drinking water supplies, and evaluating critical responses of animal model systems to the mixture. For example, these studies could: • Evaluate the toxicity/mutagenicity of representative mixtures of DBPs at moderate dose levels and evaluate their effects on the target tissues identified in animal studies and those identified in epidemiological evaluations of human populations. • Conduct in vitro assays for mutagenicity of the mixtures in comparison to individual compounds to assess any potentiating of responses. • Consider developing animal models to evaluate the potential of these DBP mixtures to act as a tumor promoter in bladder (the proposed human cancer site) and in large intestine (a tumor site for brominated DBPs observed in rodents). The human epidemiological data indicate that bladder is an important site of DBP activity in humans. This tissue has not been
