A newly published study of Texas school district data and industrial mercury-release data, conducted by researchers at The University of Texas Health Science Center at San Antonio, shows a statistically significant link between pounds of industrial release of mercury and increased autism rates. It also shows—for the first time in scientific literature—a statistically significant association between autism risk and distance from the mercury source.
The new study:
“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 is in
the journal Health & Place
Dr. Palmer, Stephen Blanchard,
Ph.D., of Our Lady of the Lake University in San Antonio and Robert
Wood of the UT Health Science Center found that community autism
prevalence is reduced by 1 percent to 2 percent with each 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.”
study should encourage further investigations designed to determine the
multiple routes of mercury exposure. “The effects of persistent,
low-dose exposure to mercury pollution, in addition to fish
consumption, deserve attention,” Dr. Palmer said. “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 new study findings are consistent
with a host of other studies that confirm higher amounts of mercury in
plants, animals and humans the closer they are to the pollution source.
The price on children may be the highest.
“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.Study highlights
Mercury-release data examined were from 39 coal-fired power plants and 56 industrial facilities in Texas.
Autism rates examined were from 1,040 Texas school districts.
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.
Autism prevalence diminished 1 percent to 2 percent for every 10 miles from the source.
exposure through fish consumption is well documented, but very little
is known about exposure routes through air and ground water.
There is evidence that children and other developing organisms are more susceptible to neurobiological effects of mercury. Implications
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
The U.S. Environmental Protection Agency (EPA)
estimated environmental mercury releases at 158 million tons annually
nationwide in the late 1990s, the time period studied by the Texas
team. Most exposures were said to come from coal-fired utility plants
(33 percent of exposures), 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.Limitations
Palmer and his colleagues pointed out the study did not reflect the
true community prevalence rates of autism because children younger than
school age are not counted in the Texas Education Agency data system.
The 1:500 autism rates in the study are lower than the 1:150 autism
rates in recent reports of the U.S. Centers for Disease Control and
Furthermore, the authors note that distance was not
calculated from individual homes to the pollution source but from
central points in school districts that varied widely in area.Data sources
for environmentally released mercury were from the United States
Environmental Protection Agency Toxics Release Inventory. Data for
releases by coal-fired power plants came from the same inventory and
from the Texas Commission for Environmental Quality. Data for school
district autism came from the Texas Education Agency.
Adapted from materials
provided by University of Texas Health Science Center at San Antonio.Further Questions
Lewandowski earlier criticized (see below) that distance to a point source is not necessarily related to level of exposure. While Texas is a significant source of mercury emissions, depending on the mercury species being emitted, the mercury from these emissions is largely deposited hundreds to thousands of miles to the east. Lewandowski therefore argues that is highly unlikely that mercury emitted in a particular county or school district can be correlated with air mercury exposures in that locality. Journal
Raymond F. Palmer, Stephen Blanchard, Robert Wood, Proximity to point sources of
environmental mercury release as a predictor of autism prevalence,
Health & Place (2008), doi:10.1016/j.healthplace.2008.02.001.
Raymond F. Palmer, Steven Blanchard, Zachary Stein, David Mandell, Claudia Miller, Environmental mercury release, special education rates, and autism disorder: an ecological study of Texas
, Health & Place, 12/2 (2006) 203-209. doi:10.1016/j.healthplace.2004.11.005
Gayle C. Windham, Lixia Zhang, Robert Gunier, Lisa A. Croen, Judith K. Grether, Autism Spectrum Disorders in Relation to Distribution of Hazardous Air Pollutants in the San Francisco Bay Area
, Environ. Health Perspect., 114/9 (2006) 1438-1444. doi:10.1289/ehp.9120
Robert Nataf, Corinne Skorupka, Lorene Amet, Alain Lam, Porphyrinuria in childhood autistic disorder: Implications for environmental toxicity
, Toxicol. Appl. Pharmacol., 214 (2006) 99-108. doi:10.1016/j.taap.2006.04.008
Thomas A. Lewandowski, Questions
regarding environmental mercury release, special education rates, and
autism disorder: An ecological study of Texas by Palmer et al.
, Health & Place, 12/4 (2006) 749-750. doi:10.1016/j.healthplace.2005.10.005 Related EVISA Resources EVISA Journal database: Journals related to "Public, Environmental and Occupational Health" EVISA Journal database: Journals related to "Toxicology" EVISA Link database: Information related to autism EVISA Link database: Information about the toxicity of mercury and its compounds EVISA Link database: Information about environmental mercury pollution Related News
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last time modified: May 14, 2008