December 18, 2014
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Prenatal exposure to household chemicals associated with lower child IQ

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Children exposed to two common household chemicals, di-n-butyl phthalate and di-isobutyl phthalate, during pregnancy had significantly lower IQ scores than children exposed to lower levels of the chemicals, according to recent study findings.

Pam Factor-Litvak, PhD, associate professor of epidemiology at the Mailman School of Public Health at Columbia University, and colleagues measured prenatal urinary metabolites to assess exposure to five phthalates during the third trimester of pregnancy among 328 mothers from inner-city communities. They included: di-n-butyl phthalate (DnBP), butylbenzyl phthalate (BBzP), di-isobutyl phthalate (DiBP), di-2-ethylhexyl phthalate (DEHP) and diethyl phthalate. The Wechsler Intelligence Scale for Children was administered to children at age 7 years to measure four areas of cognitive function associated with IQ.

Pam Factor-Litvak

Pam Factor-Litvak

DnBP and DiBP are found in numerous consumer products, including dryer sheets, vinyl fabrics, lipstick, hairspray, nail polish and some soaps, according to a press release. Several phthalates have been banned from toys and other childcare products in the United States since 2007.

Overall, child IQ was inversely associated with prenatal urinary metabolite concentrations of DnBP (b=–2.69; 95% CI, –4.33 to –1.05) and DiBP (b=–2.69; 95% CI, –4.22 to –1.16).

Children of mothers with the highest quartile DnBP and DiBP metabolite concentrations had IQs 6.7 (95% CI, 1.9-11.4) and 7.6 (95% CI, 3.2-12.1) points lower, respectively, compared with children of mothers with the lowest quartile metabolite concentrations.

Significant inverse relationships existed between maternal prenatal metabolite concentrations of DnBP and DiBP and child processing speed, perceptual reasoning and working memory.

Maternal prenatal metabolite concentrations of DiBP were inversely associated with child verbal comprehension and concentrations of BBzP were inversely associated with child perceptual reasoning.

“Comparison of concentrations of phthalate metabolites in our study to those in the last reported NHANES data find, as expected, slightly higher concentrations among women in our sample,” Factor-Litvak and colleagues wrote. “However, the confidence intervals in our data and the NHANES data overlap substantially, suggesting that the concentrations in our study are still relevant.”

Robin Whyatt

Robin M. Whyatt

Because avoiding all phthalates is not possible in the US, according to the release, the researchers recommended pregnant women limit exposure by not microwaving food in plastics, avoiding scented products such as air fresheners and dryer sheets, and not using recyclable plastics labeled 3, 6 or 7.

“The magnitude of these IQ differences is troubling,” study researcher Robin M. Whyatt, DrPH, said in the release. “A six- or seven-point decline in IQ may have substantial consequences for academic achievement and occupational potential.”

Disclosure: The researchers report no relevant financial disclosures.