Science News - May 21, 2011

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Chemicals linked
to kids’ lower IQs

By Janet Raloff

Children exposed in utero to substantial levels of neurotoxic pesticides have somewhat lower IQs by the time they enter school than do kids with virtually no exposure, three studies find.

The researchers screened women for exposure to organophosphate compounds such as chlorpyrifos, diazinon and malathion. These bug killers, which can cross the human placenta, work by inhibiting brain-signaling compounds. Although the pesticides’ residential use was phased out in 2000, spraying on farm fields remains legal.

By Alexandra Witze

All three studies began in the late 1990s and followed children through age 7. In more than 300 low-income Mexican-American families, exposures came mostly from farmwork, researchers from the University of California, Berkeley and their colleagues report. In two comparably sized New York City populations, exposures probably traced to bug spraying of homes or eating treated produce.

From high above the South Pole, Earth’s ozone hole can affect rainfall as far away as the tropics, scientists have found.

Thinning ozone pulls weather patterns southward in the Southern Hemisphere, bringing more rain to a band that includes eastern Australia and the southwestern Indian Ocean, researchers report online April

21 in Science.

Among the California families, the average IQ for the 20 percent of children with the highest prenatal organophosphate exposure was seven points lower compared with the least-exposed group.

Previous studies have shown how annual ozone thinning affects polar weather by cooling the upper atmosphere.

Sarah Kang, a postdoc-
toral fellow at Columbia
A Columbia University study followed
low-income black and Hispanic mothers.
Each additional 4. 6 picograms of chlor-
pyrifos per gram of blood in a woman
during pregnancy correlated with a drop
of 1. 4 percent in her youngster’s IQ and
2. 8 percent in a measure of the child’s
working memory.

University’s engineering school in New York City, and her colleagues wanted to see if these changes stretch toward the equator.

Before the ozone hole

The scientists used computer simulations to

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SCIENCE/AAAS

A more diverse group of Ne w York City
families recruited by the Mount Sinai
School of Medicine points to genetics as a
major determinant of risk. Children who
Fraser University in Vancouver. That’s
concerning, he says, because a drop of
seven IQ points “is a big deal. In fact,
half of seven IQ points would be a big
deal, especially when you see this across
a population.”
Each IQ-point drop will add up to
extra costs in lost earnings over an
individual’s lifetime, he says—and
even, potentially, to higher education
and other costs to deal with behavioral
and learning problems that may occur
during childhood.

Ozone loss makes subtropics rainier
Antarctic hole changes weather patterns almost to equator

model how climate would behave with and without the ozone hole, then compared those findings with observations of rainfall from 1979 to 2000. The models with the ozone hole best matched the rainfall record for that period, which saw lots of precipitation between about 15° and 35° S latitude.

The shift happens, Kang says, because ozone loss causes a westerly atmospheric jet to move further south, which pulls a mid-latitude band of dry air south. The region near the equator, in turn, gets wetter.

With the ozone hole
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The 1989 Montreal Protocol banned many ozone-destroying chemicals, and scientists expect the hole to recover by midcentury. But rising levels of greenhouse gases also push atmospheric jets southward, so global warming may counteract any changes from the healing ozone hole, says Nathan Gillett of Environment Canada’s climate modeling center in Victoria.