New federal data shows autism rates are booming. Local researchers are finding industrial chemicals may play a role

On the short list for problem chemicals are such known neurotoxins as lead, methylmercury, organophosphate insecticides, polychlorinated biphenyls, as well as arsenic, manganese, and ethyl alcohol, Landigan writes. "This short list of chemicals … may be only the currently visible tip of a potentially much larger problem," he continues. "Children today are at risk of exposure to 3,000 synthetic chemicals produced in quantities of more than 1 million pounds per year."

Children and developing fetuses are not only the most at risk from such exposures, but researchers have also found that babies are sometimes exposed to hundreds of such chemicals before they are even born.

These are the "high-production-volume chemicals" that frequently appear in consumer goods, including cosmetics and building materials, and are routinely found in air, food, and drinking water. Landrigan has found about 100 of those high-production chemicals to be neurotoxic to adult brains. Most of these chemicals are newly created substances, entering the human environment for the first time in the decades since World War II.

Palmer's interest was inspired by his own son's autism diagnosis. He chose mercury because it represented the "low-hanging fruit." Not only is it one of the most neurotoxic substances in the world, but among such it's also one of the most ubiquitous. While state and federal warnings about mercury in fish hinges on methylmercury, which is more readily absorbed by the body, the raw "elemental" version belched by power plants and absorbed by breathing it in, is also hazardous, remaining in the tissue longer, in fact, than methmercury.

Armed with U.S. Environmental Protection Agency data on ambient air quality at the city-block level, his team found in a paper published last year in the Reviews on Environmental Health that the areas of highest exposure to airborne mercury corresponded closely with the actual incidence of autism in Bexar County as tracked by the Texas Education Association. The group used data from the EPA's 2002 Toxic Release Inventory showing CPS Energy's coal plants were discharging an estimated 600 pounds of mercury into the air at Calaveras Lake. Though that number declined for a few years, it shot up to 684 pounds in 2010 when the new Spruce Two coal plant was fired up. Other sources of mercury tracked included a pair of coal-fired cement plants farther north that were releasing 25 and 11 pounds per site, according to TRI data. The team's results were duplicated with a different point source when they turned their attention to Santa Clara County, California.

Though such a statistical study doesn't provide a definitive link to mercury (these facilities put out a range of potentially harmful chemicals, not just mercury, that could play a role), it does suggest a correlation between toxic exposure and illness more generally. "It just makes sense that the environment interacts with genes," said Palmer. "Even the CDC says that virtually all disease is a function of both genetics and the environment. We just don't know which environmental trigger. It's not just mercury, it's not just nickel, pesticides. We just don't know."

> Email Greg Harman