Researchers at Mount Sinai School of Medicine have found that exposure during pregnancy to a family of pesticides called organophosphates may impair child cognitive development. The findings are published online in Environmental Health Perspectives.
From 1998 to 2002, the Mount Sinai Children's Environmental Health Study enrolled a multiethnic population of more than 400 women in their third trimester of pregnancy. The research team collected urine samples during pregnancy and analyzed them for the evidence of metabolized pesticides. The women were then invited to participate in follow-up interviews when their children were ages 12 months, 24 months, and six to nine years.
At 12 and 24 months the children were assessed using the Bayley Scales of Infant development, which is a standardized instrument that measures cognitive and psychomotor development in young children. Between the ages of six and nine years, the researchers administered skill and intelligence tests. The researchers found that exposure to organophosphates negatively impacted perceptual reasoning, a measure of nonverbal problem-solving skills.
"Manufacturers withdrew chlorpyrifos and diazinon, two types of organophosphate pesticides, from the residential market. Despite this, general population exposure to organophosphate pesticides is ongoing," said Stephanie Engel, PhD, who led the study while on faculty at Mount Sinai School of Medicine.
"We have previously reported that prenatal exposure to these pesticides was negatively related to measures of neurobehavioral organization and early markers of central nervous system development in newborns. These new findings show that detrimental effects continue to be seen on cognitive development in early childhood, particularly in subgroups of the population that metabolize these compounds less efficiently," Dr. Engel said.
Dr. Engel's team also examined the influence of variants in a key enzyme that metabolizes organophosphates, paraoxonase 1 (PON1). They found that the negative effects of organophosphates were limited to children of mothers who carried a genotype associated with a less efficient version of this enzyme.
"Nearly a third of the mothers in this study carried the PON1 genotype that would put their children at highest risk of negative effects from organophosphate pesticide exposure," said Dr. Engel, who is currently Associate Professor of Epidemiology at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill. "These highly susceptible individuals may account for the majority of exposure-related cognitive impairment. However, it's not clear how the changing nature of general population exposure following the ban on residential use will impact our understanding of these effects. Exposure source may play an important role, and exposure through diet may now be the predominant source of exposure for the general population rather than indoor pest control."
Dr. Engel added, "Our study will be published along with two independent studies that examined prenatal organophosphate pesticide exposure in relation to childhood IQ using similar research methods. There are definite similarities in our findings that, taken as a whole, warrant careful consideration."
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