Lower IQ in children linked to banned insecticide
A common household insecticide still having consequences 10 years later
Exposure in the womb to a common household insecticide is linked to deficits in IQ and working memory when the child reaches seven years old, a U.S. study has found.
Until banned for indoor residential use in the U.S. in 2001, chlorpyrifos was one of the most widely used insecticides for home use. Canada phased it out at around the same time for households but continues to allow it to fight mosquitoes in controlled environments.
Researchers from the Columbia Centre for Children's Environmental Health in New York report evidence of a link between prenatal exposure to chlorpyrifos and lower scores on two different scales of the Wechsler Intelligence Scales for Children at age seven. Virginia Rach, deputy director of the Columbia Center for Children's Environmental Health, says the banned insecticide could still have implications for school performance. Virginia Rach, deputy director of the Columbia Center for Children's Environmental Health, says the banned insecticide could still have implications for school performance. Courtsey of Columbia University.
On average, children who had exposures in the upper 25 per cent of the exposure distribution will score, on average, 5.3 points lower on the test of working memory, and 2.7 points lower on full-scale IQ, as compared to children in the lowest levels of exposure.
"Working memory problems may interfere with reading comprehension, learning and academic achievement, even if general intelligence remains in the normal range," said Virginia Rauh, lead author of the study.
The evidence suggests there is no threshold below which exposures are completely safe. Since the ban, exposure to chlorpyrifos has measurably declined.
The Columbia researchers had previously reported that, prior to the ban, chlorpyrifos was detected in 100 per cent of personal and indoor air samples, and 70 per cent of umbilical cord blood collected from babies. They also reported that the amount of chlorpyrifos in babies' blood was associated with neurodevelopmental problems at age three.
This is the first study to evaluate the neurotoxicity of prenatal chlorpyrifos at seven years of age.
The study was published online in Environmental Health Perspectives. Two other studies have also found early cognitive and behavioural effects associated with prenatal exposure to chlorpyrifos.