On the One Hand, Fewer Mosquitoes; On the Other, Increased Autism

With mosquito-borne diseases like Zika and West Nile floating around, many locales elect to control for them by spraying pesticides. A new pilot study might cause them to rethink their strategy. GlowImage/Getty Image
With mosquito-borne diseases like Zika and West Nile floating around, many locales elect to control for them by spraying pesticides. A new pilot study might cause them to rethink their strategy. GlowImage/Getty Image

It's not accurate to declare that pesticides can cause the group of developmental disorders known as autism spectrum disorder (ASD). Nobody knows exactly what causes autism, though many experts agree that it's probably a combination of genetic and environmental factors. Still, a new study links a higher incidence of autism with aerial pesticide exposure.

Muddying up the study's findings, though, is the argument that pesticides are seemingly a necessity these days. They keep disease-carrying, crop-chomping insects at bay.


"We know that pesticides do a great job of controlling mosquitoes, and mosquitoes that can carry really deadly types of diseases, like West Nile virus, or Eastern equine encephalitis, or now emerging is the Zika virus," says Steven D. Hicks, a Pennsylvania pediatrician and the lead author on the latest paper linking pesticides and autism. "So I think it's premature to trade a known risk factor for developmental issues — like the Zika virus — for this [the association with autism], which is a potential link."

Hicks presented an abstract of the upcoming paper on his study — "Aerial spraying to combat mosquitos linked to increased risk of autism in children" — at the Pediatric Academic Societies meeting in Baltimore in early May. The study, which centered on pesticide spraying in a swampy area of central New York, showed that children living in the region with aerial spraying were 25 percent more likely to be diagnosed with autism spectrum disorder than those in areas where pesticides were distributed differently.

Besides autism, pesticides have been tied to a number of other ills. For example, California is the leading U.S. agricultural producer, and it uses around 200 million pounds, or 90.7 million kilograms, of pesticides yearly. The state's health department says, "Chronic exposure (greater than 1 year) to some types of pesticides may aggravate asthma symptoms; other types may increase the risk for certain types of cancers and birth defects, or cause damage to the genetic and immune systems."

The number of people diagnosed with autism has exploded in the past two decades. Much of that, as this study suggests, may simply be an increase in how the disorder is diagnosed; that children previously went undiagnosed, or were diagnosed with another disorder.

But the numbers are the numbers. Data from the 2014 National Health Interview Survey estimates that 1 child in 45 may have ASD now (the latest figures are for 2014). It was 1 in 150 as recently as 2000.

So a study that puts pesticides and autism together is bound to arouse emotions.

"Pesticides obviously show significant links. These are toxins," says Alycia Halladay, the chief science officer of the Autism Science Foundation. "But the bottom line is that for autism, it's not just one thing. It's not going to be just pesticides, it's not going to be just air pollution. There's a strong genetic component that, together with a number of environmental factors, lead to an autism diagnosis."

For those particularly skittish about pesticides, a solution may be simple. Avoid them. Pregnant women and small children, especially. Be careful.

That means staying indoors when pesticides are being used. Covering children's play areas. Watching how you use pesticides around the house.

And, when eating foods that have been sprayed with pesticides, taking these steps recommended by the U.S. Environmental Protection Agency and Oregon State University:

•    Eat a variety of fruits and vegetables. That limits the potential of increased exposure to a single pesticide.

•    Thoroughly wash all produce, even if it's organic and even if you plan to peel it.

•    Wash under running water rather than soaking or dunking.

•    Scrub firm fruits and vegetables, like melons and potatoes.

•    Discard the outer layer of leafy vegetables.

•    Peel fruits and vegetables.

•    Trim fat and skin from meat, poultry and fish to minimize pesticide residue.

None of that is going to completely protect against an autism diagnosis. But considering the public-health nightmare we would have by getting rid of pesticides — those Zika-carrying mosquitoes — it's probably the best we're going to do.

And for the nervous among us, that should be OK. Because simply blaming pesticides for autism is a little too simplistic anyway.

"It's going to be a complicated story," Halladay says. "But I think in the past five years, there's really been an acknowledgement by both sides — both the environmental scientists and the genetics people — that it's not an either/or story. It's not that we should be fighting against each other because [the cause of ASD] is one or the other. It's definitely both."