Chlorpyrifos is an insecticide that has been widely used to control cockroaches, fleas, termites and to control crop pests. In 1997, chlorpyrifos was withdrawn from most indoor and pet uses. Chlorpyrifos is a white crystal-like solid with a strong odour.
Chlorpyrifos enters the environment through direct application to crops, lawns and domesticated animals. It may also enter the environment through spills and the disposal of chlorpyrifos waste.
It has a low water solubility (0.7 mg/l) and a high tendency to adsorb to particles and soils. Therefore it's unlikely to end up in the marine ecosystem. It has a high volatility causing it after use to usually evaporate into the atmosphere , where it is degraded rapidly. It, however, only evaporates slowly from water bodies, mainly because, in water, chlorpyrifos is associated to suspended particles. In water it is slowly hydrolysed with a half-life of less than 60 days. 
Chlorpyrifos is very toxic for crustaceans, especially amphipods which die when exposed to concentrations above 0.1 µg/l. Concentrations which cause acute toxicity in fish range, depending on the species, from 1 µg/l to 500 µg/l. In humans, chlorpyrifos can cause cholinesterase inhibition; it can overstimulate the nervous system causing nausea, dizziness, confusion, and at very high exposures, respiratory paralysis and death.
Environmental standards and legislation
- U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 1997 TOXICOLOGICAL PROFILE FOR CHLORPYRIFOS
- www.pesticideinfo.org August 20 2009
- U.S. EPA 2002 Interim Reregistration Eligibility Decision for Chlorpyrifos
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