Prenatal exposure to pesticides linked to lower IQ in children
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A new study posted on the website of the journal of Environmental Health Perspectives suggests that exposure to low levels of organophosphate pesticides during pregnancy can lower children's IQ at the age of 7 years.
Organophosphate pesticides are known neurotoxins that at high doses can harm brain development, according to the study report.
Brenda Eskenaza of the University of California, Berkeley and colleagues conducted a birth-cohort study of Latino farm worker families in an agricultural community in California and found high prenatal exposure to pesticides was linked to lower IQ in children aged 7 years.
Dr. Eskenazi early reported that prenatal exposure to pesticides was also associated with increased risk of attention deficit hyperactivity disorder or ADHA in children.
For the current study, the researchers measured dialkyl phosphate or DAP metabolites in urine collected during pregnancy from children aged 6 months, 1, 2, 3.5 and five years. Three hundred twenty nine 7-year old Children's intellectual capability was assessed on the Wechster Intelligence Scale for Children-IV.
The concentrations of pesticide metabolites in urine were found similar in the first and second half period of pregnancy. Thus the average concentrations during the pregnancy were used for analyses.
The researchers found "the average maternal DAP concentrations were associated with poor scores for working memory, processing speed, verbal comprehension, perceptual reasoning and full scale IQ."
To be specific, those with highest exposure to organophosphate pesticides had 7-point lower IQ compared with those who had the lowest exposure even though the cognitive scores were not consistently correlated with children's urinary DAP levels.
Eskenazi et al. concluded that "prenatal, but not postnatal DAP levels were associated with poorer intellectual development in 7 year old children."
They also said that "maternal urinary DAP concentrations in the present study were higher, but nonetheless within the range of levels measured in the general U.S. population," suggesting that "some U.S. women in the general population may experience OP pesticide exposure at levels that are associated with poorer cognitive development in offspring in the present study."
Stephanie M. Engel of Mount Sinai School of Medicine in New York, NY and colleagues also reported in the same journal similar observations that prenatal exposure to pesticides may lower children's IQ.
Engel et al. followed 404 children in the Mount Sinai Children's Environmental Health Study. They tested urinary levels of organophosphate metabolites in 360 mothers and children's intellectual capability was assessed at 12 months, 24 months and 6 to 9 years.
Engel found prenatal total dialkyl phosphate metabolite level was correlated with a decrease in mental development at 12 months among blacks and Hispanics. The association was more significant among children whose mothers carried the Paraoxonase 1 Q192R QQ genotype. Paraoxonase 1 is a key enzyme involved in the metabolism of organophosphates.
In later childhood, higher levels of the pesticide metabolites were associated with a decrease in perceptual reasoning.
In the same journal, Virginia Rauh of Columbia University in New York, New York also found exposure to pesticide Chlorpyrifos, a common agricultural pesticide during pregnancy can also lower children's IQ.
Their Columbia Center for Children's Environmental Health study of 265 children showed that deficits in working memory index and full scale IQ in children aged 7 years were associated with prenatal exposure to chlorpyrifos.
Rauh et al early reported the same evidence among children aged 3 years.
These studies did not investigate the sources of pesticide exposure. People can be exposed to pesticides via use of foods and drinking water, and home and personal use of pesticides, and some occupational environment.
The Environmental Working Group reported that 12 fruits and vegetables that contain highest levels of pesticides are peaches, apples, sweet bell peppers, celery, nectarines, strawberries, cherries, lettuce, grapes (imported), pears, spinach, and potatoes.
Previous studies suggest exposure to pesticides also increase risk of certain serious diseases including multiple sclerosis, epilepsy, Parkinson's disease and Alzheimer's disease.
David Liu
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