Behavior as an early indicator of pesticide toxicity.

Adverse behavioral effects are now a recognized outcome of exposure to many industrial and environmental chemicals. Pesticides occupy a special role, however, because so many of them, particularly insecticides, are designed specifically to act on neural tissue. The evaluation of behavioral toxicity is a new kind of challenge to pesticide toxicology because of the enormous structural and chemical heterogeneity of the nervous system and the even greater complexity of behavior. Determining that a particular agent is neurotoxic is not an overwhelming problem; even elementary screens are capable of detecting nervous system activity. The greater challenge is to evaluate toxicity in the context of risk assessment, which requires techniques and experimental protocols capable of detecting the subtle manifestations that tend to appear early in the course of a toxic process. A combination of advanced behavioral methods, coupled with an emphasis on tracing the responses of individual organisms, is often optimal for achieving such a goal.