Researchers have found a link between a fetus’ exposure to two common household chemicals and a lower IQ among the children several years later.
The scientists from Columbia University’s Mailman School of Public Health published their research in the journal PLoS ONE last month. In a news release, they described how children exposed during pregnancy to elevated levels of di-n-butyl phthalate (DnBP) and di-isobutyl phthalate (DiBP) had an average IQ score more than six points lower than children exposed to those chemicals at lower levels.
DnBP and DiBP are found widely in consumer products ranging from dryer sheets to vinyl fabrics to lipstick, hairspray, nail polish and even some kinds of soap. In the U.S., according to the Consumer Product Safety Commission, six kinds of phthalates are banned from toys and other child-care products. But no measures have been taken to protect a developing fetus, such as alerts to pregnant women about potential exposure. In fact, according to the Columbia release, in the U.S., phthalates seldom are listed in a product’s ingredients.
For the study, researchers followed 328 women and their children. They assessed the mothers' exposure to four phthalates — DnBP, DiBP, di-2-ethylhexyl phthalate and diethyl phthalate — during their third trimester of pregnancy by measuring levels of the chemicals' metabolites (signals of how a body processes a substance) in urine. When they were 7, the children were given IQ tests.
Children of mothers exposed during pregnancy to the highest 25% of concentrations of DnBP and DiBP had IQs 6.6 and 7.6 points lower, respectively, than children of mothers exposed to the lowest 25% of concentrations.
The pattern held when specific aspects of IQ were tested, including perceptual reasoning, working memory and processing speed.
The researchers found no associations between the other two phthalates and child IQ.
It’s especially worrisome that, as the study’s lead author said in the news release, "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."
Another scientist involved with the research said, “A six- or seven-point decline in IQ may have substantial consequences for academic achievement and occupational potential.”
It’s impossible to avoid all phthalates in the U.S., but the researchers recommend that pregnant women try to limit their exposure by:
- not using plastic when they microwave food;
- avoiding scented products such air fresheners and dryer sheets; and
- not using recyclable plastics labeled as 3, 6, or 7.
The Columbia results advance earlier research showing an association between prenatal exposure to DnBP and DiBP and children's cognitive and motor development, and behavior when they are 3. And a couple of months ago, Columbia researchers reported a link between prenatal exposure to phthalates and risk for childhood asthma
Although it's not clear how phthalates affect child health, numerous studies show that they disrupt the actions of hormones, including testosterone and thyroid hormone. So it’s best to avoid them if you can.
To see the degree to which pregnant women are exposed to all kinds of chemicals, see our blog of a few years ago, “Dangerous Products Found in Virtually All Pregnant Women.”