Chlorpyrifos is a broad spectrum organophosphate pesticide. It is one of the most-widely used active ingredients in pesticides intended for both agricultural (field crops such as peanuts, maize, citrus) and non-agricultural (eg cockroaches, termites, fleas, ants) use. It was introduced in 1965 by Dow Chemical. The two most common trade names or brands of chlorpyrifos are Dorsban and Lorsban.

How it works: Chlorpyrifos kills insect pests by disrupting their nervous system. In humans it damages the central nervous system, respiratory system, and is a skin and eye irritant.

Risks: A US study published in January 2006 in Epidemiology stated that chlorpyrifos may play a role in male infertility. Researchers testing males undergoing fertility treatment found that those with the lowest testosterone levels had the most chlorpyrifos in their systems (‘Recent pesticides research’, published in Living Earth, Spring 2006, p.9).