If You Microwave Plastic While Pregnant, Your Kid Might Wind Up Stupid

Who doesn’t love plastic? You’re basically legally obligated to love it, that stuff is in everything. About that — it turns out that pregnant mothers exposed to high levels of two types of plastic saw an adverse effect on the intelligence of their children years later, according to a new study.

The study, helmed by Pam Factor-Litvak, associate professor of Epidemiology at Columbia and published in PLOS ONE on December 10, measured phthalate levels in 328 low-income pregnant women in the New York City area. It looked for phthalate exposure in the women by taking urine tests: di-isobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), di-2-ethylhexyl, and diethyl phthalate. Then, at age 7, the kids were all given IQ tests to see if there was any link between phthalate exposure and intelligence.

Turns out that with two of the phthalates, DiBP and DnBP, there was a pretty significant correlation:

Compared to children born to women in the lowest 25thconcentration percentile, children born to women above the 75th concentration percentile for MnBP and MiBP scored 6.6 and 7.6 points lower on 7 year IQ. Similar associations were found between these metabolites and perceptual reasoning, working memory and processing speed subscales of the WISC-IV.

Though the study found that phthalate exposure showed stronger correlations for girls and boys depending on the type of intelligence being measured, the correlations were not great enough to be considered statistically significant.

Again, this isn’t a blanket condemnation of all types of plastic; we’re specifically talking about phthalates here — di-n-butyl phthalate (DnBP) and di-isobutyl phthalate (DiBP). So what contains phthalates? Turns out, quite a number of things: air fresheners, drier sheets, recyclable plastics labeled 3, 6, and 7, and yes, many microwave-safe plastic containers. Further bad news: that new car smell we all know and love is actually the scent of phthalates volatizing off of the plastic dashboard after exposure to heat from sunlight. So if you’re pregnant, probably don’t buy a new car, either.

We’ve actually known phthalates were trouble for a while; Apple eliminated the use of phthalates in iPhone production years ago, and there have been quite a number of questions about the safety of phthalates for years now. This, however, is the first long-term study about prenatal interactions with phthalates.

So, maybe just microwave that leftover pizza on a paper towel next time, at least if you’ve got a bun in the oven.