Pregnant
women who live in smog-filled areas may be twice as likely
to have children with autism, a new study suggests. "The
study does not prove that pollution increases risk for
autism. It found an association," said the lead author. "It
adds to the weight of the evidence that there may be
something in air pollution that increases risk for autism."
Researchers compared exposure to air pollution among 325
women who had a child with autism and 22,000 women who did
not. The women were participants in the Nurses' Health Study
II. Pollutants measured included diesel particulate matter,
lead, manganese, mercury, methylene chloride, and a combined
measure of metal exposure. Twenty percent to 60 percent of
the women lived in areas considered highly polluted. And the
study showed that: those women who lived in the 20 percent
of locations that had the highest levels of diesel
particulates or mercury in the air were twice as likely to
have a child with autism, compared to those who lived in the
20 percent of areas with the lowest levels of these
pollutants. In addition, those who lived in the 20 percent
of locations with the highest levels of lead, manganese,
methylene chloride, and combined metal exposure were about
50 percent more likely to have a child with autism than
those who lived in the 20 percent of areas with the lowest
concentrations. The findings held even after the researchers
took into account other factors known to affect autism risk,
such as income, education and smoking during pregnancy.
Overall, the association was stronger for boys than it was
for girls, but the number of girls included in the new study
was too low to draw any firm conclusions. Exactly how, or
even if, air pollution affects the developing brain is
murky. "By definition, pollution is stuff that is not good
for us," the author said. Still, the overall increase in
autism risk that may be attributed to pollution is low.
"Let's say a woman's risk for having a child with autism is
one in 100, women who live in the most polluted cities have
a risk that is about one in 50, which means that 49 children
would not have autism," researcher added. |