Socioeconomics May Affect Toddlers’ Exposure to Flame Retardants.

Exposure to potentially toxic flame-retardant chemicals appears higher in non-white toddlers than in white toddlers, with differences in exposure also linked to socioeconomic factors, a study co-authored by a BUSPH researcher has found.

The study, recently published in the journal Environmental Health Perspectives, tested 83 toddlers between the ages of 12 and 36 months for levels of polybrominated diphenyl ethers (PBDEs), a class of exceptionally long-lasting chemicals widely used over the last 30 years to reduce flammability in some consumer products, including polyurethane foam padding, electronics and furniture. The study was led by Duke University researchers, with Thomas Webster, a BUSPH professor of environmental health, as a contributing author.

Hand-to-mouth activity may account for a significant amount of the children’s exposure to the contaminants, the authors said. Age and duration of breastfeeding also were associated with exposure.

The researchers detected PBDE contaminants in all of the blood and house dust samples, and in 98 percent of hand-wipe samples. Older children had higher average total body burdens of the contaminants, the study found, with average levels increasing by an estimated 60 to 70 percent for each year of age. That finding may reflect the combined effect of PBDE accumulation in the body over time and the toddlers’ increased hand-to-mouth activity, according to the study.

Duration of breastfeeding also was associated with exposure. Blood samples contained significant levels of one PBDE component that has a long half-life in the body and is strongly correlated with the amount of time a mother spends breastfeeding.

“This could be coming from PBDE exposures the mother had up to 2 1/2 years ago,” said lead author Heather Stapleton, assistant professor of environmental chemistry at Duke University’s Nicholas School of the Environment.

The authors said further research is needed to explain why white toddlers in the study averaged 32 parts per billion of PBDE chemicals in their blood serum, while non-white toddlers averaged 60 parts per billion. Also, exposure to the chemicals appeared higher among toddlers whose fathers do not have a college degree, a proxy of lower socioeconomic background.

“Race and socioeconomic status were closely associated in our test group, so it’s hard to disentangle them,” Stapleton said, “but it’s important to note that we found no significant differences in PBDE concentrations in house dust samples by race or parental education. This suggests the exposure difference is not driven solely by higher levels of PBDE in dust from lower socioeconomic homes.”

Studies have shown that over time, PBDEs accumulate in living organisms, where they can disrupt endocrine activity and impair thyroid regulation and brain development. Early exposure to PBDEs has been linked to low birth weight and impaired cognitive, motor and behavioral development.

Because children can be exposed to PBDEs three ways — by ingesting them with food or dust particles, breathing them in from the air, or ingesting them through mother’s milk — Stapleton, Webster and colleagues collected blood serum samples, hand-wipe samples and house dust samples for each child in the test group.

One of the most promising findings of the study, Stapleton said, was that hand-wipe samples turned out to be good predictors of total exposures. The samples are easier to collect than by drawing blood.

Parents or caregivers may be able to reduce toddlers’ potential exposures through more frequent hand washing and by researching, as best they can, which flame retardants are used in their household products, the authors said.

Historically, three mixtures of PBDEs have been sold under different trade names. Two mixtures, pentaBDE and octaBDE, were phased out in 2005 due to concerns about their persistence and toxicity. The third mixture, decaBDE, is slated for voluntary phase-out starting in 2013.

Being phased out doesn’t mean they no longer pose risks. “The type of PBDE we tracked in our study was from the pentaBDE mixture, which has, officially at least, been off the market for more than seven years,” Stapleton said.

Funding for the study came from a five-year, $2.2 million grant from the National Institute of Environmental Health Sciences.

Submitted by: Lisa Chedekel

chedekel@bu.edu