Maryland Legislation Requires Phase Out of Toxic Pesticide Tied to Autism

April 09, 2020

Chlorpyrifos Exposure During Pregnancy Increases Risk of Autism 

A bill requiring a ban on the insecticide chlorpyrifos passed both legislative houses1 in Maryland. Maryland joins other states 2 including California, New Jersey, Connecticut and Oregon with plans to forbid the substance.

The state bans are welcome news for future children since chlorpyrifos has been linked to lower IQ and neurodevelopmental issues, including autism. Chlorpyrifos3 is an organophosphate insecticide which inhibits neurotransmitter function by affecting the enzyme acetylcholinesterase. Organophosphates also disturb the microbiome4 of animals exposed to it.

A 2019 study5 of California mothers and their children found that the child’s risk of autism – and particularly autism with co-occurring intellectual disability – increases following prenatal exposure to ambient pesticides including chlorpyrifos. The researchers compared autism rates of children from mothers living within a radius of 2000 meters (about 1.25 miles) of agricultural fields sprayed with pesticides during pregnancy with offspring of women from the same agricultural region without such exposure.

A study from 20146, also in California, found that babies whose mothers lived within a mile of crops treated with widely used pesticides were at greater risk of developing autism. Exposure to chlorpyrifos specifically during the second trimester of pregnancy resulted in a 3.3 times greater likelihood of being diagnosed with the disorder.

The Maryland effort has been in the works for many years. Advocacy was coordinated by the Maryland Smart on Pesticides Coalition7. SafeMinds is a Coalition member. According to Ruth Berlin, Executive Director of the Maryland Pesticide Education Network which runs the Coalition, Maryland Governor Larry Hogan has until the end of April to approve or veto the bill, and there are no indications that the Governor won’t see it enacted.

The action of Maryland and other states follows the reversal in 20178 of a decision by the U.S. Environmental Protection Agency (EPA) to phase out the substance at the federal level, even after its own expert committee recommended such a step in 2015.

Chlorpyrifos was eliminated from residential use in 2001. It is still widely used on crops to control pests, including corn, soybeans, almonds, alfalfa, vegetables and fruits. In Maryland, it poses a danger to the health of the Chesapeake Bay as well as children, since pesticide runoff from farm fields can hurt aquatic life. It is a poison to bees and other pollinators.

With so many states as well as the European Union9 moving to end the use of chlorpyrifos, Corteva Agriscience (formerly DowDupont), the maker of the largest-selling chlorpyrifos brand Lorsban, announced it would stop producing chlorpyrifos at the end of 2020, citing declining sales.


[1] Maryland General Assembly. Pesticides – Use of Chlorpyrifos – Prohibition.

[2] Bloomberg Environment. Maryland Passes Ban on Chlorpyrifos Pesticide, Sends to Governor. March 19, 2020.

[3] Chlorpyrifos – Wikipedia.

[4] Xianling Yuan, et al. Gut microbiota: An underestimated and unintended recipient for pesticide-induced toxicity. Chemosphere. Volume 227, July 2019, Pages 425-434.

[5] von Ehrenstein Ondine S, Ling Chenxiao, Cui Xin, Cockburn Myles, Park Andrew S, Yu Fei et al. Prenatal and infant exposure to ambient pesticides and autism spectrum disorder in children: population based case-control study BMJ 2019; 364 :l962.

[6] UC Davis Health Newsroom. UC Davis MIND Institute study finds association between maternal exposure to agricultural pesticides, autism in offspring. June 22, 2014.

[7] Smart on Pesticides Maryland.

[8] Beyond Pesticides. Maryland Legislature Passes Limited Ban on Chlorpyrifos Insecticide. Daily News Blog. March 24, 2020.

[9] Sam Levin. Largest maker of pesticide linked to brain damage in kids to stop producing chemical. February 6, 2020.

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