Commonly-Used Insecticides Could Raise Autism Risk: Study

Autistic children pose for a picture taken by a specialised teacher Caroline Berge (L) at the College du Parc in Aulnay-sous-Bois, northeast of Paris on October 9, 2019. Photo by Christophe ARCHAMBAULT/AFP via Getty Images

Early exposure to a class of insecticides called pyrethroids could raise the risk of autism and other developmental disorders, even if the exposure is at levels deemed safe by federal regulators, new research has uncovered.

Pyrethroids are one of the most widely used insecticides in the United States. They appear in both industrial preparations and consumer products. Several regions known for widespread pesticide use have documented higher rates of neurodevelopmental disorders (NDD). In the United States, as many as 17 percent of children are estimated to be affected by NDDs. The new study, published in the journal PNA Nexus on April 25, looked at the effects of low-level exposure to pyrethroids.

In their tests, researchers exposed female mice to small doses of pyrethroid insecticide deltamethrin before, during, and immediately after pregnancy. The concentrations were “well below the benchmark dose used for regulatory guidance.”

They then examined the offspring of the mice and found that the offspring exhibited increased hyperactivity, repetitive behaviors, and less vocalization.

The offspring experienced disruptions in their dopamine system and were also more likely to fail in basic learning tests when compared to control mice.

Dopamine plays a key role in reward and movement regulation in the brain. A dysfunction in the dopamine system has been implicated in multiple diseases of the nervous system.

“These are all similar to symptoms human patients with neurodevelopmental disorders might have,” said Dr. James Burkett, an assistant professor of neuroscience in the UToledo College of Medicine and Life Sciences and the paper’s corresponding author, according to an April 25 press release.

“Something in their brain has been altered by this exposure, and it’s resulting in the same kinds of behaviors that we see in children with autism.”

Pyrethroids and Autism Risk

Pyrethroids are similar to the natural pesticide pyrethrum that is produced by chrysanthemum flowers. They are found in household insecticides, shampoos, and pet sprays. Some pyrethroids, used as mosquito repellants, are applied directly to clothes. Others are used for lice treatments and applied directly to the head.

In the United States, pyrethroids are used in mosquito control as an ultra-low volume spray. Such sprays release tiny aerosol droplets into the air, which ends up killing mosquitoes on contact.

“If you have someone who comes and sprays in your house, this is likely what they’re spraying. It’s used in landscaping, it’s what they fog in the streets for mosquitos. It’s everywhere,” Burkett said.

The U.S. Environmental Protection Agency has evaluated pyrethroids used in the country and deemed that these chemicals pose very little risk to human beings when used in line with label directions. However, the April 25 study challenges such assumptions.

“This study adds to a growing body of literature that the widely used pyrethroids are not without adverse effects and should be further evaluated for their safety,” said Dr. Gary Miller, vice dean for research strategy and innovation at Columbia University Mailman School of Public Health and a co-author on the study.

Autism in the US

The research into insecticides like pyrethroids potentially contributing to autism is crucial, given that the disorder has been rising among children across the United States in the past years.

According to data from the CDC, only one in 150 children reported autism spectrum disorder (ASD) in the country in 2000. Two decades later, in 2020, this has jumped to one in 36.

During a study period from 2009–2017, one in six children in the age group of 3 to 17 years old were diagnosed with a developmental disability, including autism, cerebral palsy, and attention-deficit/hyperactivity disorder, among others.

Meanwhile, the latest research suggests that an epilepsy drug can “switch off” autism. According to a study published in February in the journal Molecular Psychiatry, the drug lamotrigine, which is sold under the brand name Lamictal, was found to curb behavioral issues associated with ASD.

Lamotrigine was approved for use in the United States back in 1994. They are also inexpensive, with thirty 100 mg tablets costing as little as $3.