Abnormal behaviours induced by chemical pollution: a review of the evidence and new challenges

Many chemical pollutants have become ubiquitous in the environment, including some that interfere with hormones and other physiological mechanisms. These ‘endocrine-disrupting chemicals’ (EDCs) have harmful effects on development and physiology. We reviewed published evidence and found that EDCs also have adverse effects on a wide range of behaviours, including sexual and other reproductive behaviours, activity, motivation, communication, aggression, dominance and other social behaviours, and learning and other cognitive abilities. We also reviewed recent findings that challenge common assumptions in toxicology. For example, EDCs have several unanticipated properties, such as nonmonotonic dose effects and synergy. Furthermore, harmful effects of EDCs sometimes become apparent only when tested in natural ecological conditions, such as social stress and infection. These findings raise questions about the practicality and feasibility of testing chemical pollutants adequately. Finally, we discuss the implications of EDC research for species conservation and human health, and how toxicology and behavioural research might be better integrated. Behaviour might provide a useful indicator or biomarker for detecting harmful chemical contaminants; however, more integration between toxicology and behavioural ecology is needed to determine whether and how EDCs affect humans and other vertebrates outside of the laboratory.