Prenatal Exposure to Pollution Raises Risk of
Autism in Kids
The
national study of in utero exposure and autism rates raises new concerns. Researchers
at the Harvard School of Public Health (HSPH) say that early-life exposure to
pollution, including diesel particulates, mercury and lead, could contribute to
a higher risk of autism disorders.
They
came to that conclusion after analyzing data from a nationwide sample of
116,430 nurses participating in the Nurses’ Health Study II, an ongoing survey
that began in 1989. Among the volunteers, 325 had children with autism, and
most of them lived in areas with higher levels of pollutants than those who
didn’t have children affected by the developmental disorder. Last year, a study of
over 500 kids found that those with autism were two to three times more likely
than other kids to have been exposed to car exhaust, smog and other air
pollutants early on. But those studies involved mothers and children in limited
geographic areas; in the current study, published online in the journal Environmental
Health Perspectives, the scientists surveyed pollution exposure and
autism rates across the entire U.S.
They
compared autism rates with levels of pollutants measured by the U.S.
Environmental Protection Agency during the womens’ pregnancies. Expectant
mothers who lived in the 20% of locations around the country with the highest
pollution levels in the form of diesel particulates or mercury were two times
as likely to have a child with autism compared with those who lived in the 20%
of locations with the lowest levels of pollution. Women who lived in the 20% of
areas with the highest levels of other pollutants, like lead, manganese,
methylene chloride and other metals, were nearly 50% more likely to have a
child with autism.
“Our
results suggest that new studies should begin the process of measuring metals
and other pollutants in the blood of pregnant women or newborn children to
provide stronger evidence that specific pollutants increase risk of autism,”
said senior study author Marc Weisskopf, an associate professor of
environmental and occupational epidemiology at HSPH in a statement. “A better
understanding of this can help to develop interventions to reduce pregnant
women’s exposure to these pollutants.”
Documenting
the effect that prenatal exposure can have on children’s development could help
to untangle some of the conflicting evidence about how pollutants may
contribute to autism and other disorders such ascancer, hyperactivity and obesity. The connection between air pollution and weight gain
was quite dramatic; researchers measured polycyclic
aromatic hydrocarbons (PAHs) found
in cigarette smoke and car exhaust and found that kids born to mothers
with the highest PAH levels during their third trimester had a 79% greater risk
of becoming obese. By the time the kids turned 7, their risk was more than 2.25
times higher, most likely because the chemicals can disrupt hormones that regulate
growth and development.
It’s
still not clear how each of the pollutants may be hampering normal childhood
development, but toxic buildup could result from blood vessels that contract or
harden prematurely in an effort to protect tissues from excess exposure to the
chemicals. That idea is supported by some studies in adults that have linked
exposure to air pollution with hardening of the arteries and a higher risk of heart
disease.
While
it’s no surprise that exposure, even in utero, to potentially harmful chemicals
found in the air can adversely affect children’s brains and bodies, studies
like Weisskopf’s that reveal these correlations are the first step toward
figuring out which pollutants are especially harmful and which agents are most
closely tied to certain diseases. That in turn could lead to smarter ways of
measuring these agents in expectant mothers’ blood and possibly intervening
with treatments to reduce or even prevent some of these conditions.
Read more: http://healthland.time.com/2013/06/18/prenatal-exposure-to-pollution-raises-risk-of-autism-in-kids/#ixzz2bJqNPu56
Read more: http://healthland.time.com/2013/06/18/prenatal-exposure-to-pollution-raises-risk-of-autism-in-kids/#ixzz2bJqNPu56
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