TOLEDO, Ohio — Breathing in a class of insecticides called pyrethroids could increase your risk for neurodevelopmental disorders, warns a new study. Pyrethroids are one of the most common insecticides in the country. These include lice treatments and mosquito repellents like permethrin (Biomist®), resmethrin (Scourge®) and sumithrin (Anvil®).
“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,” says study author James Burkett, an assistant professor of neuroscience in the University of Toledo’s College of medicine and life sciences.
These aren’t just commercial-grade products, you can buy these bug sprays in stores as well. At household levels, federal regulators have deemed the insecticide harmless to humans. However, the new study shows that the chemicals are a danger even at “safe” levels.
There have been several population studies documenting a higher rate of neurodevelopmental disorders with low-level exposure to pyrethroids. To study the specific behavioral changes from inhaling insecticide spray, the authors looked at the offspring of female mice exposed to small doses of a pyrethroid called deltamethrin before, during, and immediately after pregnancy.
Babies showed increased hyperactivity and repetitive behaviors, fewer vocalizations, and were more likely to fail basic learning tests. They also experienced changes in their dopamine system, a feature characteristic of a number of neurodevelopmental disorders.
“These are all similar to symptoms human patients with neurodevelopmental disorders might have,” Burkett explains in a university release. “We are not saying these mice have autism or that they have ADHD. That’s not the goal here. What we are saying is that 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.”
The findings build on previous attempts to understand the harms of pest control chemicals.
“We have reduced our exposures to many classes of dangerous pesticides over the past few decades through restrictions and regulations,” says Gary Miller, a vice dean for research strategy and innovation at Columbia University Mailman School of Public Health and study co-author. “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.”
Autism cases are rising in the U.S. The rate grew from one in 150 children in 2000 to one in 44 children in 2018, according to the Centers for Disease Control and Prevention. One of the problems with identifying the causes of autism and neurodevelopmental disorders is that most research focuses on the genetic component.
“That’s why this kind of research is so important,” emphasizes Burkett. “You can’t change someone’s genetics, but you can address environment[al] factors.”
Pyrethroids are one of many classes of pesticides that could contribute to autism.
“This research represents a piece of the puzzle. It is not definitive proof that the pesticide is unsafe or directly causing autism in humans,” Burkett says. “It may, however, suggest that the safe level of the pesticide needs to be revisited for pregnant women and children.”
The study is published in PNAS Nexus.
What is autism?
Autism, or autism spectrum disorder (ASD), is a complex neurodevelopmental disorder characterized by differences in social interaction, communication, and behavior. It is called a spectrum disorder because it affects individuals in different ways and to varying degrees. People with autism may have difficulties with social skills, repetitive behaviors, speech, and nonverbal communication, but they can also possess unique strengths and talents.
The exact cause of autism is still not fully understood, but it is believed to involve a combination of genetic, environmental, and neurological factors. There is no single known cause, and research is ongoing to better understand the disorder. Early diagnosis and intervention are important for improving outcomes and helping individuals with autism lead fulfilling lives. Treatments for autism may include behavioral therapy, speech therapy, occupational therapy, and other support services tailored to the specific needs of the individual.