The bad news about phthalates and children — particularly boys — just keeps coming. Phthalates have already been linked to ADHDbreast enlargement and smaller testicles in boys. Now it seems researchers have found a link between exposure to chemical additives and IQ scores.

Researchers from four medical schools in Korea recruited third- and fourth-grade children from nine grade schools across the country. Their sample size was small — only 667 kids — but it did represent a broad and nationally representative cross-section of South Korea’s children, including kids from metro areas, suburban homes and rural communities.  

For the study, each child took the Korean version of a widely accepted IQ test known as the Wechsler Intelligence Scale for Children, or WISC. The kids’ moms also took the test, results that researchers used as a gauge for the genetic component to each child’s IQ (more on this in a moment.)

They also measured the DEHP metabolites, or the broken-down phthalates, for each child and split them into four groups on the basis of these metabolites. In their research, published in the journal, Environmental Health Perspectives, the researchers report that as the amount of DEHP’s metabolites in urine climbed, a child’s IQ dropped by a couple of points — but only for boys. No such trend emerged among girls.

What to make of all of this? Well, I'm not sure how scientifically valid it is to control the kids' scores on the basis of their moms’ IQ scores. For starters, they are excluding kids whose moms have passed away or kids who are being raised by stepmoms or adoptive moms. Also, the moms’ IQs might have influenced — through healthier diet choices or product purchases — their children's exposure to phthalates in the first place.

But even though this study may not be able to draw any conclusive parallels between boys' IQ scores and exposure to phthalates, I think it's safe to assume that these chemicals are not healthy for children — particularly boys.