For years, the question of whether pesticides are linked to autism has driven environmentalists to protest and driven academics mad. And while scientists have yet to prove the root cause of autism, it just so happens that pesticides continue to crop up in research as suspected culprits or contributors. Most recently: Pediatric researchers from Penn State University and the University of California found that communities significantly more exposed to a type of mosquito-killing pesticide were also significantly more likely to have higher rates of autism diagnoses in kids.
It also just so happens that the type of pesticide in question, a pyrethroid, is a rather common, EPA-approved skeeter-exterminator sprayed all across the Gulf Coast and the country — and Harris County and Galveston County are just two examples.
The new study, peer-reviewed and published in Frontiers in Pediatrics, examined eight ZIP codes in Onondaga County, New York, with high exposure to mosquito pesticide through aerial sprays. The pesticide sprays there are intended to squash the West Nile virus, especially in Onondaga's region called Cicero Swamp.
Compared to 16 control ZIP codes without such pesticide use, the eight exposed communities in Onondaga County were 37 percent more likely to have higher rates of autism diagnoses or developmental delays in kids. (The researchers — led by Dr. Steven D. Hicks, an associate professor of pediatrics at Penn State — pooled all the kids' medical information and diagnoses from SUNY Upstate, the only regional children's hospital in an 80-mile radius.)
Still, the authors were quick to note that these findings in no way prove that mosquito pesticides cause autism — but the results certainly raise some questions.
"Although this study is observational and does not establish a causal relationship between pyrethroid exposure and [autism and developmental delays], it adds to a growing body of literature that shows a relationship between pesticides and ASD/DD," they wrote. "To our knowledge, this is the first study to show a relationship between the route of pesticide exposure and rates of neurodevelopmental delay. It raises intriguing questions about the safety of pesticide use in our society and how the manner in which those pesticides are applied might affect brain development in children."
So to what extent are these types of mosquito pesticides used locally — and to what extent should residents be concerned?
Dr. Mustapha Debboun, director of Harris County Mosquito Control, said that more studies are likely warranted, but that this should not be cause for alarm. Harris County uses a type of pyrethroid called permethrin (as well as a different chemical called malathion) — but not on a regular basis. The only times Harris County sprays, Debboun said, are when technicians discover virus-carrying mosquitoes in a specific pocket of the county and need to prevent the spread of disease. Sprays are isolated to that single area, he said.
"We don't spray every day or whenever we want to," he said. "We spray when the data tells us that the mosquitoes are hot with a virus. For example, this Friday, one pool of mosquitoes was hot with the West Nile virus, so we sprayed Sunday. We haven't sprayed since February."
It's a bit of a different story in Galveston County, where Galveston County Mosquito Control is, in fact, out every day spraying permethrin in the spring, malathion in the summer and naled — another controversial pesticide — about 25 times a year from an airplane. The agency sprays different parts of the county each day, said Director John Marshall, and so each community is sprayed in total about three times per month.
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Marshall dismissed recent research connecting both pyrethroid pesticides and naled to public health risks or autism, saying that the pesticides are intended to protect people from disease, not hurt them. He called environmentalists in Miami, who staunchly fought against the use of naled to fight the Zika virus during the outbreak last year, a "bunch of damn tree huggers." Naled is banned by the European Union because of several studies linking long-term exposure to developmental effects on fetuses, but is approved by the EPA.
Marshall maintained that the sprays are necessary to prevent mosquito-spread diseases and keep down the mosquito population in one of Texas's most tourist-friendly counties.
"We're highly regulated. We watch [the chemicals] very close, and we just don't have problems — we're just using such low dosages," Marshall said. "That's why these reports bother me, because you'll get environmentalists who think there just shouldn't be any pesticides in the world, and they're gonna do everything they can to try to stop it. They're not considering those poor kids standing out at the bus stop. They're not considering that people buy a home and a backyard to be able to barbecue and entertain without getting carried away [by mosquitoes]. What do you do if you have a disease outbreak if you don't have anything to spray?"
What do you do if the cure for the disease is linked to other disease too? Until such a link can be proven, Marshall said, the skeeter spraying will go on.