Chlorpyrifos and Nervous System Disrorders

The organophosphate pesticide chlorpyrifos is a broad-spectrum insecticide used to kill a wide variety of insects. It remains one of the most widely used agricultural organophosphate (OP) insecticides, and is currently in use in more than 100 countries worldwide, including the United States. It also acts as acaricide and miticide and is used to control foliage and soil-borne insect pests. Prior to June 2000, CPF was also widely used for indoor pest control and pet collars, but most household uses were phased out beginning in June 2000 and canceled by January 2001. Therefore, the primary route of exposure to the general U.S. population of children and adults today is dietary. Children and adults, including pregnant females, who are farm workers or living on or near farms may be exposed through additional pathways, including dermal or inhalation routes.

Chlorpyrifos is highly toxic to aquatic organisms including fish. It bioaccumulates in fish and has at least three main modes of action in mammals. It inhibits the enzyme acetylcholinesterase (AChE), causes oxidative stress and endocrine disruption.1 In humans, chlorpyrifos can cause nausea, dizziness, confusion, and at high exposures, it may cause lung cancer, respiratory paralysis and death. The metabolite, 3,5,6-Trichloro-2-pyridinol(TCP), CAS number 6515-38-4, is a toxic chemical which was found to lower testosterone levels in men.

Children living near rice fields have higher organophosphate insecticides exposure which is a concern, particularly given previous studies documenting developmental disorders, delays in mental development, behavioral problems, poorer short-term memory and motor skills, and longer reaction times among children with long-term OP exposure. Studies have also found associations between exposure and Attention Deficit/Hyperactivity Disorder (ADHD), including prenatal exposures and current exposure linking urinary metabolite levels for OPs with increased diagnosis of ADHD.3


  1. Modifying Effects of Vitamin E on Chlorpyrifos Toxicity in Atlantic Salmon. Pål A. Olsvik,* Marc H. G. Berntssen, and Liv Søfteland
  2. Changes of Field Incurred Chlorpyrifos and Its Toxic Metabolite Residues in Rice during Food Processing from-RAC-to-Consumption. Zhiyong Zhang et al.
  3. Characterizing exposures and neurobehavioral performance in Egyptian adolescent pesticide applicators. Diane Schertler Rohlman et al.