Children exposed to high levels of the common household chemicals di-n-butyl phthalate (DnBP) and di-isobutyl phthalate (DiBP) before birth tended to have IQ scores that were an average of six points lower than children who were exposed to lower levels.
These chemicals are found in a number of consumer products such as dryer sheets, vinyl fabrics, hairspray and lipstick. Since 2009, many phthalates have been banned from children's toys, but little has been done to alert pregnant women to protect themselves against the chemicals and they are rarely listed on product labels, Columbia University's Mailman School of Public Health reported.
"Pregnant women across the United States are exposed to phthalates almost daily, many at levels similar to those that we found were associated with substantial reductions in the IQ of children," said lead author Pam Factor-Litvak, associate professor of epidemiology at the Mailman School.
To make their findings, researchers looked at 328 New York City women and assessed their exposure to four phthalates: DnBP, DiBP, di-2-ethylhexyl phthalate, and diethyl phthalate in their third trimester of pregnancy.
The team found that children of mothers exposed to the highest concentrations of DnBP and DiBP had IQs 6.6 and 7.6 points lower, respectively, than children with lower exposure rates. These findings remained after controlling factors such as "maternal IQ, maternal education, and quality of the home environment that are known to influence child IQ scores."
"The magnitude of these IQ differences is troubling," said senior author Robin Whyatt, professor of environmental health sciences and deputy director of the Columbia Center for Children's Environmental Health at the Mailman School. "A six- or seven-point decline in IQ may have substantial consequences for academic achievement and occupational potential."
Researchers recommend pregnant women limit their exposure by not microwaving food wrapped in plastics and avoiding scented products such as air fresheners and dryer sheets.
The findings were published in a recent edition of the journal PLOS ONE.
