Environmental exposure to pesticides, both before birth and during the first year of life, has been linked to an increased risk of developing autism spectrum disorder, according to the largest epidemiological study to date on the connection.

The study, published Wednesday in BMJ, found that pregnant women who lived within 2,000 meters (approximately 1.2 miles) of a highly-sprayed agricultural area in California had children who were 10 to 16 percent more likely to develop autism and 30 percent more likely to develop severe autism that impacted their intellectual ability. If the children were exposed to pesticides during their first year of life, the risk they would develop autism went up to 50 percent.