Do Flame Retardants Make Us Dimmer?
When I was in the second trimester of pregnancy, my husband and I bought a new king-sized mattress. Like all cotton mattresses sold in the U.S., ours had been treated with a flame retardant containing polybrominated diphenyl ethers (PBDEs) and/or organohalogen compounds (OHCs). Flame retardants are also in pillows, car and airplane seats, drapes, rugs, and insulation. They’re in electronic equipment, like TVs, and in the dust on top of TVs. They’re in air and soil and breast milk. Almost all humans have flame retardants flowing through their veins.
Around the same time I got my new mattress (on which I tossed and turned in third trimester), two surprising studies were published on the effects of flame retardants on fetuses and young children.
A group of researchers at the University of Gronigden in the Netherlands recruited nearly 70 pregnant women in third trimester, taking samples of their blood and measuring it for PBDEs and OHCs. Five years later, the children were given standardized developmental tests for motor skills (balance and coordination), cognition (intelligence, spatial skills, control, verbal memory, and attention), and behavior.
The result: PBDEs were correlated with worse performance on fine motor tasks and a shortened attention span. Strikingly, they were also linked with better coordination and visual perception, as well as better (more placid?) behavior. OHCs, meanwhile, were correlated with worse fine motor skills. Oddly, these kids had better visual perception.
Researchers at Columbia University tested for PBDEs in the cord blood of nearly 400 women who delivered their babies at a New York City hospital. These children were given mental and motor development tests in infancy and, later, at four-to-six years. These tests measure memory, problem solving, habituation, language, mathematical concept formation, and object constancy. They also assess ability to manipulate hands and fingers and control and coordinate their movements.
The result: At both age intervals, children who had higher cord blood concentrations of PBDEs scored significantly lower on tests of mental (lower IQ) and motor development. This was particularly evident at age two for motor skills and age four for IQ (nearly 8 points lower for certain PBDEs).
Are flame retardants slowing us down? Correlation is not causation, but there’s a real risk that they do — and researchers have some ideas about how these chemicals have a toxic effects on the brain. OHCs (for instance) have been found to decrease a fetus’s production of thyroid hormone by interfering with thyroid receptors. This leads to an increase in thyroid stimulating hormone (TSH). Brain development in the fetus relies on the precise timing and quantity of thyroid hormone; too much or too little causes developmental delays. High prenatal exposure to TSH is associated with lower IQs – 4 points less on average. During critical developmental periods, PBDEs and OHCs may also have a toxic effect on neurons in the hippocampus, the memory region of the brain, by reducing the number of neurotrasnmitter receptors.
Infants and toddlers have what researchers call a high “body burden” of flame retardants. Household dust, which floor-playing infants and toddlers encounter constantly, accounts for 80-93 percent of postnatal PBDE exposure, followed by breast milk (however, the benefits of nursing appear to outweigh this drawback; breastfed babies score higher on neurodevelopmental tests).
A disturbing fact is that American kids have levels of PCBEs that are 10 to 1,000 times higher than their peers in Europe or Asia. We produce 1.2 billion pounds of the stuff annually. (Interestingly, the Scandivanian study, whose subjects had lower levels of prenatal exposure, found no IQ deficit while the U.S. study did.) Consider our nation’s problems: attention deficit disorder, placidity, lower standardized test scores in reading and math.
Are flame retardants making kids dimmer?
The question fires up the imagination. Should pregnant women be advised to avoid, say, dusting and buying new mattresses in the same way we avoid emptying the litter box (to avoid toxoplasmosis)? Are the perceived gains in visual perception real, and, if so, why, and do they come at the expense of other abilities? Are urban kids at a higher risk than average? Are there naturally flame-retardant materials that we can use in lieu of chemicals? More research, especially on American kids, is warranted.
After all, the nightmare scenarios can keep an expectant mom up all night, tossing and turning on her nonflammable mattress.
* If you wish, check out my forthcoming book, Do Chocolate Lovers Have Sweeter Babies: The Surprising Science of Pregnancy.