More flame retardants found in house dust knowledge on the persistency and bioaccumulative nature of HCDBCO,” Zhu says. It is also unclear what consumer products contain HCDBCO, and the European Brominated Flame Retardant Industry Panel (EBFRIP) was unable to provide this information in time for this article. Mohamed Abdall ah
New research published in ES&T (pp 386–391) identifies for the first time a flame retardant known as HCDBCO (hexachlorocyclopentadienyldibromocyclooctane) in the environment and shows that it can be found at high levels in Canadian homes. A second paper published in ES&T (pp 459–464) reports that a U.K. home contains the highest concentrations ever documented in residential dust of another more well-known flame retardant, HBCD (hexabromocyclododecane). Together, the papers suggest that people in the developed world may be exposed to significant concentrations of flame retardants beyond PBDEs in their homes. A team of Canadian researchers led by Jiping Zhu of Health Canada discovered HCDBCO in archived samples collected from Ottawa homes in 2002 and 2003. The compound’s unusual composition made identification a real challenge, Zhu says. “This is the first flame retardant detected in the environment that contains both chlorine and bromine,” he points out. Because the researchers could not obtain a commercial source of the compound, they synthesized their own standard and used it to analyze 69 representative archived dust samples for HCDBCO. Although most of the samples had relatively low concentrations of the compound (less than 40 nanograms per gram of dust), two contained elevated concentrations of 18 micrograms per gram (µg/g) and 93 µg/g. Zhu and his colleagues found the same lognormal distribution pattern when they looked for the compound in 55 archived indoor air samples. In air, the overall concentrations of HCDBCO were higher than those of the major PBDE congeners. More data are needed on HCDBCO’s toxicity and on human exposure to the compound, the Canadian researchers stress. In addition, “there is no conclusive
This U.K. home was 1 of 52 residences in three countries in which researchers looked for HBCD in house dust.
In the second study, led by Stuart Harrad of the University of Birmingham (U.K.), researchers looked for HBCD in dust from 31 homes in the U.K., 13 in the U.S., and 8 in Canada. Although the concentrations of the contaminant in each country’s dust were statistically indistinguishable, one U.K. home harbored outlier levels of 110 µg/g. HBCD is used in polystyrene insulation and textiles. Toxicology studies have suggested that the compound can alter the uptake of neurotransmitters in rat brains, affect thyroid hormone function in rats, and induce cancers in humans, according to Harrad and his colleagues. However, a spokesperson from EBFRIP disputes this assessment of the toxicological
data and argues that “recent evidence . . . indicate[s] that the thyroid effects observed in rats are not expected to occur in humans.” Scientists suspect that children are at the highest risk from dustborne contaminants because they are thought to consume much more dust than adults. Harrad cautions that no one knows exactly how much dust the average person ingests. The study nonetheless estimates that a toddler living in the U.K. home with the highest concentration of HBCD could—per unit of body weight—be exposed to substantially higher concentrations of the flame retardant than an adult working in a manufacturing facility where HBCD is used. Flame retardant experts agree that the new papers are important because they suggest that HBCD and HCDBCO have the same lognormal distribution pattern in homes as PBDEs and the commonly used flame retardant Dechlorane Plus. This distribution pattern could help explain why a minority of people in North America and Europe harbor significantly higher concentrations of PBDEs in their bodies than the rest of the population. “I think that this lognormal distribution [pattern] is what you have to expect for the distribution of compounds such as flame retardants in people’s homes,” says Andreas Gerecke of the Swiss Federal Laboratories for Material Science and Technology. The implications are significant “once you start to think about all the chemicals in dust that children are exposed to . . . [including] PAHs, PCBs, DDT, chlordanes, etc.,” points out Heather Stapleton, an assistant professor at Duke University’s Nicholas School of the Environment and Earth Sciences. “No one is addressing the bigger picture of synergistic or additive effects from exposure to these mixtures,” Stapleton says. “It’s like we’re letting our children play in a chemical soup bowl, and that’s a little scary.” —KELLYN BETTS
January 15, 2008 / Environmental Science & Technology ■ 337
