A recent study from University of Chicago scientists suggests that various environmental toxins can increase the risk of autism in children. The analysis of over 100 million U.S. medical records showed how autism risk can be influenced by the environment.

“Autism appears to be strongly correlated with rate of congenital malformations of the genitals in males across the country,” said study author Andrey Rzhetsky, professor of genetic medicine and human genetics at the University of Chicago. “This gives an indicator of environmental load and the effect is surprisingly strong.”

The studies showed that for every one percent increase in genital birth defects in boys, autism rates rose by nearly 300 percent. They also found that male children with autism are nearly six times more likely to have congenital genital deformities. Female incidence of autism was only weakly linked with increased genital malformation.

According to the study, male fetuses are particularly sensitive to toxins such as medications, environmental lead, sex hormone analogs, and other synthetic molecules. It is thought that parental exposure to these toxins may explain many congenital reproductive malformations.
Almost all geographic areas with higher autism rates also had higher incidences of intellectual disability, which the study authors believe validates the presence of environmental factors.

As autism and many other intellectual disabilities may carry genetic components, researchers note that it does not take away from the fact that environmental factors can increase the risk of the disorder and its development in the human body.

For the study, Rzhetsky and his team researched data sets on insurance claims that had information on nearly a third of the American population. Over time, they noted that state regulation was not keeping up with current research taking place.

“We interpret the results of this study as a strong environmental signal,” Rzhetsky said. “For future genetic studies we may have to take into account where data were collected, because it’s possible that you can get two identical kids in two different counties and one would have autism and the other would not.”

The study was published in PLOS Computational Biology on March 13.