WASHINGTON — Pregnant women with higher levels of a banned pesticide that’s still found in many foods today are more likely to have children diagnosed with autism, a new study finds.

Dichlorodiphenyltrichloroethane, or DDT, is an insecticide widely used after its development in the 1940s. It’s particularly known to help prevent malaria, typhus, and other insect-borne diseases. Of course, it was also extremely useful for farmers and anyone else who found themselves frequently bugged by insects. The pesticide became commonly used across the world, but by the late 1950s, its dangerous effects on the environment and wildlife began to come into light; consequently in 1972, as it became clearer that it was unhealthy for human exposure, the Environmental Protection Agency banned its use in America.

Despite the ban, DDT is still showing up in our food decades later. The EPA warns the chemical is “known to be very persistent in the environment,” and “can travel long distances in the upper environment.” It continues to be found across the food chain, particularly in vegetables, fish, meat, and dairy products, according to the advocacy group Toxic-Free Future. DDT is of particular concern to unborn children because it can still transfer across the placenta.

In this latest research published in the American Journal of Psychiatry, researchers examined maternal serum samples from 778 children with autism as well as matched control cases (children of similar ages, genders, etc., but without autism). They found that a child was at greater risk of autism when their mothers showed elevated levels — 75th percentile or greater — of DDE in their blood. For pregnant women with the highest levels of DDE, a child’s risk of autism with intellectual disability were twice as high.

The authors warn that the results are strictly observational, and that a cause-and-effect was not proven.

“These findings provide the first biomarker-based evidence that maternal exposure to insecticides is associated with autism among offspring,” the authors write. “Although further research is necessary to replicate this finding, this study has implications for the prevention of autism and may provide a better understanding of its pathogenesis.”

The study was published August 16, 2018.

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