Chapter 41 - Cumulative Effects of Organophosphorus or Carbamate Pesticides

Abstract

The chapter is designed to address issues of experiment design of mixture studies; summarize the available literature on organophosphate (OP) pesticide mixtures, carbamate (CM) pesticide mixtures, and mixtures of OP and CM pesticides; and address future research priorities. The chapter considers N-methyl CMs or cholinesteraseinhibiting CMs, and not thio or dithiocarbamates, which have other mechanisms of toxicity. Therefore, only OP and CM pesticides that inhibit cholinesterase are considered. In the literature describing the toxicity of mixtures of OP or CM pesticides, concern is expressed that exposure to mixtures of pesticides may be much more toxic than the toxicity of individual pesticides. This concern about potentiated toxicity is all the more worrisome because there is lack of data on the toxicity of pesticide mixtures, whether OP or CM, at less than lethal dosages. Because the ratio of the OP or CM pesticides in the mixture, the sequence of administration, and the timing of the administration can all have a marked influence on the toxicity profile of a mixture, more research investigating these relationships is needed to define comprehensively the interaction profile of a group of pesticides. Only a very small percentage of the mixture studies in the literature used more than two anticholinesterase pesticides, whereas in the real world, humans are routinely exposed to many more than two chemicals.