According to researchers at Columbia University’s Mailman School of Public Health, children exposed during pregnancy to elevated levels of two common chemicals found in the home—di-n-butyl phthalate (DnBP) and di-isobutyl phthalate (DiBP)—had an IQ score, on average, more than six points lower than children exposed at lower levels.
ColumbiaPublicHealth study is the first to report a link between prenatal exposure to phthalates and IQ in school-age children.
Prior research reports inverse associations between maternal prenatal urinary phthalate metabolite concentrations and mental and motor development in preschoolers. No study evaluated whether these associations persist into school age.
In a follow up of 328 inner-city mothers and their children, we measured prenatal urinary metabolites of di-n-butyl phthalate (DnBP), butylbenzyl phthalate (BBzP), di-isobutyl phthalate (DiBP), di-2-ethylhexyl phthalate and diethyl phthalate in late pregnancy. The Wechsler Intelligence Scale for Children, 4th edition was administered at child age 7 years and evaluates four areas of cognitive function associated with overall intelligence quotient (IQ).
Child full-scale IQ was inversely associated with prenatal urinary metabolite concentrations of DnBP and DiBP: b = −2.69 (95% confidence interval [CI] = −4.33, −1.05) and b = −2.69 (95% CI = −4.22, −1.16) per log unit increase. Among children of mothers with the highest versus lowest quartile DnBP and DiBP metabolite concentrations, IQ was 6.7 (95% CI = 1.9, 11.4) and 7.6 (95% CI = 3.2, 12.1) points lower, respectively. Associations were unchanged after control for cognition at age 3 years. Significant inverse associations were also seen between maternal prenatal metabolite concentrations of DnBP and DiBP and child processing speed, perceptual reasoning and working memory; DiBP and child verbal comprehension; and BBzP and child perceptual reasoning.
Maternal prenatal urinary metabolite concentrations measured in late pregnancy of DnBP and DiBP are associated with deficits in children’s intellectual development at age 7 years. Because phthalate exposures are ubiquitous and concentrations seen here within the range previously observed among general populations, results are of public health significance.
Sources and more information
- Persistent Associations between Maternal Prenatal Exposure to Phthalates on Child IQ at Age 7 Years, PLOS one, DOI: 10.1371/journal.pone.0114003, December 10, 2014.
- Exposure During Pregnancy to Common Household Chemicals Associated with Substantial Drop in Child IQ, Columbia University’s Mailman School of Public Health, Dec. 10, 2014.
- Phthalates risk damaging children’s IQs in the womb, US researchers suggest, theguardian, 10 December 2014.