Pesticide-induced immunotoxicity: Are humans at risk?

One of the first immunotoxicology studies determined that exposure of ducks to DDT reduced their resistance to a virus infection. The immunotoxic potential of insecticides and herbicides has subsequently been studied extensively in laboratory animals, driven by the global distribution and use of these chemicals. (Ten of the twelve persistent organic pollutants, identified by the United Nations Environmental Program as posing the greatest threat to humans and wildlife, are pesticides; all have been reported to alter immune function under laboratory conditions.) Nevertheless, our knowledge of the human health risks associated with pesticide use and exposure is far from complete. This paper provides a brief overview of the potential effects of chemicals on the immune system, and host factors that mitigate or exacerbate immunotoxic effects. Examples of rodent studies that exemplify categories of pesticide-induced immune system effects are then provided as an introduction to a discussion of pesticide immunotoxicity in humans.