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Environmental Factor, July 2012

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Study links house dust with high risk of exposure to flame retardant chemicals

By Ashley Godfrey

Heather Stapleton, Ph.D.

Stapleton, an assistant professor of environmental chemistry at the Duke University Nicholas School of the Environment, feels very strongly about the potential health risks of PBDE exposure in young children and is doing everything she can to help spread public awareness. Stapleton spent the early part of her career working under the guidance of NIEHS/NTP Director Linda Birnbaum, Ph.D., who is recognized as a leading authority on flame retardant research. (Photo courtesy of Duke University Nicholas School of the Environment)

Illustration of baby's exposure to polybrominated diphenyl ethers (PBDEs)

Young children have very high hand-to-mouth activity and are, therefore, at increased risk of exposure to PBDEs through house dust. Stapleton suggested that regular handwashing, along with education and the practice of other clean behaviors, may help to lower the amount of exposure. (Photo courtesy of Environment California)

In a new NIEHS-funded study of polybrominated diphenyl ethers (PBDEs), chemicals used as flame retardants, NIEHS Outstanding New Environmental Scientist (ONES) awardee Heather Stapleton, Ph.D., and colleagues found that toddlers have a significant amount of exposure to PDBEs through house dust.

The findings, published online in Environmental Health Perspectives, suggest that hand-to-mouth activity may be a significant source of exposure for children 12 to 36 months of age. Children’s exposure to these chemicals is a concern, because many studies, both in animals and humans, have shown that PBDEs have potential endocrine disrupting effects and may have harmful effects when exposures occur during critical periods of neurodevelopment. PBDEs have chemical structures similar to thyroid hormones.

According to Stapleton, indoor dust levels of PBDEs are higher than most people would expect, and are surprisingly similar to the levels she and her colleagues found in a related study that measured PBDEs in municipal sewage sludge.

From house dust to hands

One of the primary objectives of this study was to better characterize children’s exposure to PBDEs from house dust, while also examining the relationship between PBDE exposure and other variables that may affect exposure. The study enrolled 83 children in North Carolina and measured PBDE levels in blood and hand wipe samples taken from each child, as well as in house dust samples. The researchers found a strong correlation between the PBDE levels found on the hand wipes and the levels measured in the blood.

The findings suggest that toddlers have a significant amount of exposure to PBDEs by transferring house dust particles from their hands to their mouths. This suggests exposure to other household dust contaminants, such as pesticides, polycyclic aromatic hydrocarbons (PAHs), perfluorinated compounds (PFCs), and other types of flame retardants, may occur the same way. PAHs are produced as byproducts of burning fuel, while PFCs are found in products that resist stains, oil, and water. All of these contaminants are believed to pose a human health risk.

The methods used in this study also suggest the value of using hand wipes as a tool to measure children’s exposure to different chemicals found in dust. “Hand wipes might be a better route to measure exposure,” Stapleton said.

Other risk variables

The study also found other factors that may contribute to exposure levels, including age, socioeconomic status, and duration of breastfeeding. While these factors may be significant predictors of exposure levels, the study points out that further research is needed to explore why these factors are influencing PBDE exposure in children. This information may help in mediating the potential health risks from exposure, by increasing public awareness about what other factors contribute to exposure.

When asked about the importance of this line of research, Stapleton said the study is only one of many that she feels are necessary, in order to gather as much information as possible about children’s exposure to PBDEs and other chemicals found in dust, to understand the potential health risks that may come from this type of exposure.

Public health concerns

Although two forms of PBDEs, pentaBDE and octaBDE, were phased out of use in the U.S. in 2004, and a third, decaBDE, is scheduled to be voluntarily phased out starting in 2013, it is impossible to determine exactly which household products are treated with these chemicals. Many PBDEs are known to have very long half-lives, the period of time it takes for the amount of a substance undergoing decay to decrease by half, and can potentially still find their way into house dust from older products in the home.

Stapleton is also interested in conducting future studies to investigate exposure from new flame retardants that are now on the market and are being used to replace the phased-out PBDEs. Children, as well as adults, are more likely to be exposed to a complex mixture of chemicals, instead of just one, because there are so many chemicals found in house dust. “We know very little about the health effects from exposure to complex mixtures of chemicals,” acknowledged Stapleton.

Citation: Stapleton HM, Eagle S, Sjödin A, Webster TF. 2012. Serum PBDEs in a North Carolina toddler cohort: associations with hand wipes, house dust and socioeconomic variables. Environ Health Perspect; doi:10.1289/ehp.1104802 [Online 23 May 2012].

(Ashley Godfrey, Ph.D., is a postdoctoral fellow in the Molecular and Genetic Epidemiology Group in the NIEHS Laboratory of Molecular Carcinogenesis.)

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