Good hygiene decreases exposure to toxic chemicals

PBDE flame retardants can stick to people's hands, suggesting that hand-to-mouth contact may be a major route of exposure.

We all know that we can reduce our risk of exposure to viruses and bacteria by washing our hands before we eat. New research in ES&T (DOI: 10.1021/es7029625) suggests that good hygiene may also help protect people—especially children—from taking up persistent organic pollutants (POPs) from everyday objects like TVs and cell phones.

A team led jointly by Heather Stapleton, an assistant professor at Duke University's Nicholas School of the Environment, and Tom Webster, associate chairman of the Boston University School of Public Health's environmental health department, measured the concentrations of PBDE flame retardants on the hands of 33 U.S. volunteers, including 6 children. They used sterile gauze pads in a hand-wipe procedure developed for assessing exposure to contaminants like pesticides in occupational settings.

When the researchers began the project, they weren't certain they would detect any PBDEs adhering to people's hands, Webster recalls. To their surprise, they found PBDEs on every wipe sample collected, and in some cases the levels were quite high. Plugging that data into exposure models "suggest[s] hand-to-mouth contact could be a primary route of exposure," Stapleton says.

This is important because, although food is the main source of people's exposure to most other POPs—including PCBs, dioxins, and banned pesticides like DDT—other research has made clear that food is not the major source of PBDEs and other brominated flame retardants. Earlier this year, Matt Lorber of the U.S. EPA's National Center for Environmental Assessment estimated that more than 80% of people's overall exposure to PBDEs comes from nonfood sources (J. Expo. Sci. Environ. Epidemiol. 2008, 18, 2–19). Lorber commends the new work for being among the first to provide hard data on sources of PBDE uptake other than food, noting that the new findings are in line with his estimates.

Because PBDEs are used in many consumer products and have been found in house dust, many researchers suspect that dust is a major source of PBDEs. How people are taking up that dust has been unclear, but Stapleton, Webster, and their colleagues hypothesize that "contact with PBDE-containing products (e.g., TVs, remote controls, cell phones) and/or house dust may lead to the adsorption of these chemicals to hand or skin oils." From there, the PBDEs on the skin may be inadvertently ingested if people put their hands in their mouths.

The researchers say that eating oily finger foods such as French fries, sandwiches, and chips with unwashed hands is a likely route by which people could unwittingly consume PBDEs. The paper also points out that PBDEs may be absorbed directly into the body via the skin.

The new work may help explain why the limited data available on children's exposure to PBDEs show that children can take up levels that are much higher than those of the rest of the population. Young children put their hands in their mouths much more than adults do, which in turn suggests that their exposure will be significantly higher, Webster says.

The research also "suggests that adults with higher hand-to-mouth contact frequencies, [such as] smokers [and] nail biters, may be receiving exposure . . . and maybe this explains why a small part of the population has such high exposure," Stapleton says. "PBDEs are very unusual in that we have seen some people with levels 50 times higher than the median," explains Linda Birnbaum, director of EPA's Experimental Toxicology Division. The uptake range for most other persistent and bioaccumulative chemicals is much smaller, she says.

In addition to PBDEs, Stapleton and colleagues detected other flame retardants on the hands of their study participants. She and Webster are currently trying to assess how well different hand-washing approaches remove PBDEs and other contaminants from people's hands. "I'm sure that other fat-soluble chemicals like PCBs, PAHs, and perfluorinated compounds are partitioning to the skin oils as well," Stapleton says. All of these compounds could be inadvertently ingested via hand-to-mouth contact, Stapleton and Webster point out. —KELLYN BETTS