Chlorpyrifos was patented by Dow Chemical in the 1960s and widely released as a multipurpose insecticide for a plethora of agricultural and residential applications: everything from ridding household pets of fleas to protecting cash crops from ravenous mites. Its trade names currently include Lorsban, Lock-On, and Cobalt. It was also marketed and sold for primarily residential and industrial use under the name Dursban.
Chlorpyrifos is a member of a class of chemicals called organophosphate pesticides. It should be noted that neurotoxicity is not a side effect of these chemicals; it’s precisely what they’re designed for. Chlorpyrifos acts by targeting and lethally disrupting the nervous system of its prey. It was developed to rid homes and gardens of cockroaches, ants, mites, and other vermin. But in small, continuous doses, human beings are vulnerable to its neurotoxic effects as well.
In the early 2000s, Dow entered into a deal with the EPA to voluntarily phase out the residential use of chlorpyrifos. Dow reached the agreement following a critical mass of evidence indicating that repeated exposure to chlorpyrifos in homes and schools was poisoning children. The symptoms of exposure to chlorpyrifos included diarrhea, headaches, numbness, and vomiting. But even then researchers were noting chronic mental problems linked to exposure, such as learning disabilities, memory problems, fatigue, and attention deficits.
Chlorpyrifos is still among the most commonly used pesticides in American agriculture. Its lethal efficacy is one reason it is the “Coca-Cola of growers,” as one former employee at California’s Office of Pesticides told a journalist. The Intercept reported that approximately 44,000 farms collectively use between 6 million and 10 million pounds of chlorpyrifos annually. It is applied to a variety of crops, including apples, asparagus, broccoli, cauliflower, corn, cranberries, onions, peaches, soybeans, strawberries, and walnuts.
Exposure can come to people through a variety of ways. Families that live near farms that spray chlorpyrifos on their fields are acutely affected, but through its agricultural application, the chemical finds its way into water supplies. Even for those who don’t reside or work in places where chlorpyrifos is applied, its residue can remain on fruits and vegetables that fill grocery store shelves.
Over the past several years, multiple studies have shown that prolonged exposure to the chemical hinders neurodevelopment in fetuses and young children. Research from the CHARGE study, a groundbreaking study on the environmental causes of neurodevelopmental delay, found that pregnant women exposed to the application of pesticides during their second and third trimesters gave birth to children with tripled risk for autism. A Columbia University study showed children with high levels of exposure still lagging behind their peers in mental and motor development at age three. Children with high levels of exposure were twice as likely to be mentally delayed and more than five times as likely to develop symptoms of autism. The chances of ADHD symptoms was six times higher and symptoms of other attention disorders 11 times higher with exposure.
The EPA signaled that it had accepted the science in a November 2016 report, “Chlorpyrifos Revised Human Health Risk Assessment,” that assessed previously published findings and alerted the public to the chemical’s dangers. It detailed the risks of exposing infants and pregnant women to chlorpyrifos, demonstrating a potential link to intelligence deficits, the development of autism, as well as problems with attention, memory, and motor skills.
Dow disputes these findings. A website the company maintains to air information about chlorpyrifos says: “The weight of the evidence of years – in some cases, decades – of scientific study continues to demonstrate that there is no link between chlorpyrifos and any of these health concerns.” The company has been funding its own scientific research to counter the growing consensus about the ill effects of its lucrative chemical.
Despite the established dangers, it is far from certain that chlorpyrifos will be banned in the near future. Consumer and public health advocates have been lobbying the EPA to ban the pesticide for years, without success. The November 2016 report indicates that the agency has finally acknowledged the chemical’s hazards and may move to re-regulate it, but Dow is currently preparing for a lengthy legal battle to ensure that chlorpyrifos remains on the market – not to mention in the air, in the food, and in the water.