Aerial spraying of pesticides meant to kill mosquitoes could be driving up rates of autism in children, according to new research. Such activities may also result in developmental delays in the young people, the study concludes.

Pyrethroid pesticides are sprayed into the air each summer over a swamp-filled region of central New York. The activity is meant to reduce populations of mosquitoes carrying the virus responsible for equine encephalitis, a condition which can result in swelling of the spinal cord and brain.

Children living in regions where aerial spraying took place each year were found to be 25 percent more likely to experience autism spectrum disorder and developmental delays than those youth in surrounding areas. In regions where the spraying took place, one in 120 children experienced ASD or developmental delays, compared to one in 172 in other parts of the state.

"Our findings show that the way pesticides are distributed may change that risk. Preventing mosquito-borne encephalitis is an important task for public health departments. Communities that have pesticide programs to help control the mosquito population might consider ways to reduce child pesticide exposure, including alternative application methods," Steven Hicks, assistant professor of pediatrics at the Milton S. Hershey Medical Center, managed by Penn State, said.

Autism spectrum disorder (ASD) affects the ability of children to effectively communicate and socialize with others. The condition, which affects roughly one in 68 American youths, has a wide range of symptoms. While those with mild cases may only experience minor problems in social environments, severe cases can result in subjects ignoring most of the outside world, while focusing on simple tasks.

Although this study shows a higher rate of autism in this one area where aerial spraying of pesticides takes place, there is no concrete proof that this practice causes autism spectrum disorder. Nevertheless, this is not the first time that this mosquito-eradication technique has been tied to autism. A study published in 2014 concluded pregnant women living in areas subject to aerial spraying of the chemicals were more like to birth children with the condition.

"Aerial Pesticide Exposure Increases the Risk of Developmental Delay and Autism Spectrum Disorder" will be presented as a talk at a meeting of the American Academy of Pediatrics.