Study Finds Link Between Autism Rates, Mercury Emissions

A new study of Texas school district and industrial mercury-release data, which was conducted by researchers at The University of Texas Health Science Center at San Antonio, reveals that there is a statistically significant link between the pounds of industrial release of <"">mercury and an increase in autism rates. The study examined mercury-release data from 39 coal-fired power plants and 56 industrial facilities in Texas and autism rates from 1,040 Texas school districts.

The study confirmed—for the first time in scientific literature—that there is a statistically significant link between autism risk and distance from the mercury source.  “This is not a definitive study, but just one more that furthers the association between environmental mercury and autism,” said lead author Raymond F. Palmer, Ph.D., associate professor of family and community medicine at the UT Health Science Center San Antonio.  The article appears in the journal Health & Place.

Palmer; Stephen Blanchard, Ph.D., of Our Lady of the Lake University in San Antonio; and Robert Wood of the UT Health Science Center discovered that community autism prevalence goes down by one-to-two percent for every 10 miles of distance from the pollution source.  “This study was not designed to understand which individuals in the population are at risk due to mercury exposure,” Dr. Palmer said. “However, it does suggest, generally, that there is greater autism risk closer to the polluting source.”  Palmer also said, “The effects of persistent, low-dose exposure to mercury pollution, in addition to fish consumption, deserve attention.  Ultimately, we will want to know who in the general population is at greatest risk based on genetic susceptibilities such as subtle deficits in the ability to detoxify heavy metals.”

The study revealed mounting evidence that children and other developing organisms are more susceptible to neurobiological effects of mercury.   “We suspect low-dose exposures to various environmental toxicants, including mercury, that occur during critical windows of neural development among genetically susceptible children may increase the risk for developmental disorders such as autism,” the authors wrote.

The study found for every 1,000 pounds of mercury released by all industrial sources in Texas into the environment in 1998, there was a corresponding 2.6 percent increase in autism rates in the Texas school districts in 2002; for every 1,000 pounds of mercury released by Texas power plants in 1998, there was a corresponding 3.7 percent increase in autism rates in Texas school districts in 2002.  “We need to be concerned about global mercury emissions since a substantial proportion of mercury releases are spread around the world by long-range air and ocean currents,” Dr. Palmer said. “Steps for controlling and eliminating mercury pollution on a worldwide basis may be advantageous.  This entails greener, non-mercury-polluting technologies.”

The U.S. Environmental Protection Agency (EPA) estimated environmental mercury releases at 158 million tons annually nationwide in the late 1990s, the time involved in this research.  Most exposures were said to come from coal-fired utility plants (33 percent), municipal/medical waste incinerators (29 percent) and commercial/industrial boilers (18 percent).  Cement plants also release mercury.  With the enactment of clean air legislation and other measures, mercury deposition into the environment is decreasing slightly.

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