Study leader Megan Horton of the Columbia Center for Children's Environmental Health at the Mailman School of Public Health at Columbia University and colleagues looked at a subset of 335 mother-child pairs enrolled in an ongoing inner-city study of environmental exposures, including measures of prenatal chlorpyrifos in umbilical cord blood.
Once the children reached age 3, the researchers measured the home environment using the Home Observation for Measurement of the Environment criteria, including two main categories: Environmental stimulation, defined as the availability of intellectually stimulating materials in the home and the mother's encouragement of learning; and parental nurturance, defined as attentiveness, displays of physical affection, encouragement of delayed gratification, limit setting, and the ability of the mother to control her negative reactions. The researchers tested IQ at age 7.
The study, published journal Neurotoxicology and Teratology, found chlorpyrifos exposure had a greater adverse cognitive impact in boys as compared to girls, lowering working memory scores -- a key component of IQ -- by an average of three points more in boys than girls and that parental nurturing was associated with better working memory, particularly in boys.
"There's something about boys that makes them a little more susceptible to both bad exposures and good exposures," Horton said in a statement. "One possible explanation for the greater sensitivity to chlorpyrifos is that the insecticide acts as an endocrine disruptor to suppress sex-specific hormones."