New federal data shows autism rates are booming. Local researchers are finding industrial chemicals may play a role
Published: May 2, 2012
It's for that reason that researchers are divided over how many of those new CDC numbers are truly new cases. While some media outlets have adopted the narrative of better diagnosis to explain away the statistical surge, UC Davis researcher Irva Hertz-Picciotto looked at California autism cases from 1990 to 2006, finding that better diagnosis could not explain roughly half of the new cases being seen year after year. "Certainly some of the increase is a labeling issue," Hertz-Picciotto wrote the Current in an email, "but our quantitative analysis suggested this could not explain a big portion of it."
The scientific community is also strongly divided over what causes the disorder. While the role of obesity and the age of parents has been garnering headlines of late, the big battle has been between genetics and environment. For years, environmental factors have been swept to the margins of the debate, but some influential research — increasingly by San Antonio-based researchers — is tilting the scale toward the role of chemicals in the environment.
A partnership between Our Lady of the Lake sociology prof Steve Blanchard and Ray Palmer, a doctor of preventative medicine specializing in autism at UT Health Science Center in San Antonio, has drawn a statistical link between elevated autism rates in Bexar County and areas of high ambient mercury emissions, such as occurs around CPS Energy's coal-burning power plants at Calaveras Lake and cement kilns to the north. And Dr. Claudia Miller, an allergist and immunologist, at UTHSC's School of Medicine, warns about the role of poorly regulated everyday chemicals in homes and businesses. When it comes to explaining the disorder, Miller's presentations frequently draw on the allusion of a handgun: "Genetics loads the gun; but environment pulls the trigger." That is: our bodies may be predisposed to reacting to certain chemical inputs, but it takes the presence of that chemical to flip the switch. Which chemical? Good question.
Bexar County school districts by relative risk of autism by standard deviations of ambient mercury exposures. From the report "The value of ecological studies: mercury concentration in ambient air and the risk of autism," published in the Reviews of Environmental Health last year.
"The government cannot regulate these things because there isn't sufficient information to indict one particular exposure," Miller said, "but some have found links. Researchers in California, for instance, have shown that mothers who spray their dogs with flea and tick spray double their probability of having a child with autism. So there are these little hints."
Though ongoing research will certainly shed more light on the ultimate causes of the disorder — nearly a billion dollars have been spent studying it in the last decade, according to the Associated Press — what's becoming clear is that genetic factors may account for far fewer cases than previously thought, according to Philip Landrigan of the Mount Sinai School of Medicine. In his 2010 paper "What causes autism? Exploring the environmental contribution," Landrigan describes the detrimental impact prevalent everyday chemicals are already known to have on the brain.
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