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Prenatal Exposure To Pesticides Linked To Lower IQ

April 21, 2011

Results from three separate studies suggest that prenatal exposure to pesticides is linked to lower intelligence scores in children than those who were not exposed, according to reports published in the journal Environmental Health Perspectives.

The three separate studies ““ two done in New York and one done in Salinas, a farming area in northern California ““ tracked levels of pesticides in pregnant women over a span of almost ten years, and tested about 1,000 children up to the age of nine.

Exposure to a family of pesticides, known as organophosphates, was examined in the studies. These pesticides are commonly used in fruit and vegetable fields.

Researchers at the University of California Berkeley tested 392 kids and found that “every tenfold increase in measures of organophosphates detected during a mother’s pregnancy corresponded to a 5.5 drop in overall IQ in the seven-year-olds,” even after accounting for factors such as education, family income and exposure to other environmental contaminants, reports AFP.

Researchers at Mount Sinai Hospital, New York found that “exposure to organophosphates negatively impacted perceptual reasoning, a measure of non-verbal problem-solving skills” between the ages of six and nine.

In addition, out of the 400 women in the study, Mount Sinai researchers found that the negative effects in children were limited to a group of approximately one-third of mothers who carried a gene variant that made them less able to metabolize the pesticides, AFP reports.

In the third study at New York’s Columbia University, researchers focused on the pesticide chlorpyrifos, which, until 2001, was widely used in homes to kill cockroaches and termites.

265 minority children, born before chlorpyrifos ban took effect, were sampled and researchers found that higher prenatal exposure was linked to lower intelligence scores and poorer memory.

The top 25% of children exposed to high levels of the pesticide scored 5.5% lower in working memory tests and 2.7 points lower in IQ tests.

Lead author Virginia Rauh of the Columbia Center for Children’s Environmental Health says, “These observed deficits in cognitive functioning at seven years of age could have implications for school performance.”

“Working memory problems may interfere with reading comprehension, learning and academic achievement, even if general intelligence remains in the normal range.”

“That difference could mean, on average, more kids being shifted into the lower end of the spectrum of learning, and more kids needing special services in school,” says Eskenazi, the lead researcher in the Berkeley study.

The studies were independent of one another, but the similar results raises concerns, says lead author of the California study, Maryse Bouchard.

“It is very unusual to see this much consistency across populations in studies, so that speaks to the significance of the findings,” she says.

Eskenazi describes the associations as “substantial, especially when viewing this at a population-wide level.”

Berkeley researchers say that organophosphate pesticide use has declined more than 50% between 2001 and 2009; however diazinon and chlorpyrifos are still being used in agricultural fields. Diazinon was found to be a neurotoxicant that posed a health risk for children and was ban in 2004, reports AFP.

“It is vitally important that we continue to monitor the levels of exposure in potentially vulnerable populations, especially in pregnant women in agricultural communities, as their infants may continue to be at risk,” says Dr. Robin Whyatt of Columbia.

Presently, exposure to these pesticides would likely be from eating foods treated with them, reports AFP. It is recommended by experts that produce should be washed by rubbing it through running water to remove any residue.

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