PBDEs and PCBs in Computers, Cars, and Homes
Note that both pentaBDE and octaBDE have been nominated for inclusion in the Stockholm Convention.
16.11.2006 |Sonja Haider
Environmental Science and Technology
November 1, 2006
The emissions from older computers can be more toxic than previously thought.
Older computers can be a significant source of toxic polybrominated diphenyl ether (PBDE) flame retardants, according to research published today on ES&T’s Research ASAP website (DOI: 10.1021/es0617082). The study also finds that air inside older automobiles is an important source of PBDEs and that newer homes can harbor unidentified sources of PCBs.
Stuart Harrad, who is an environmental chemist at the University of Birmingham (U.K.) and the paper’s corresponding author, stresses that serendipity played a major role in his discovery that older computers can be a significant source of lighter PBDEs, which are more toxic than their heavier counterparts. Harrad and his coauthor Sadegh Hazrati stumbled across the new data only because they happened to be monitoring PBDE levels in an office where a computer purchased in 1998 was replaced with a newer model. After the new computer was put in place, total PBDE concentrations in the office air dropped by more than 75%, from 431 picograms per cubic meter (pg/m3) to less than 95 pg/m3.
These indoor air PBDE levels aren’t terribly high in comparison with what is being found in North America, where people’s PBDE levels tend to be 10 times those of Europeans. But the sharp drop that Harrad’s group recorded is particularly noteworthy because the researchers did not measure levels of the heavier PBDE compounds, or congeners, associated with the Deca formulation of PBDEs used in electronics products.
Hazrati, who analyzed the data as a graduate student, was “very worried that he’d done something wrong,” Harrad remembers. [hee hee, what a funny image!] At the time, in October 2004, most researchers familiar with brominated flame retardants believed that the only PBDEs found in computers were associated with the heavier Deca formulation.
“This paper highlights the problem [of] relying upon information from industry sources regarding applications of commercial [PBDE formulations] to specific types of products,” says Heather Stapleton, an assistant professor at Duke University’s Nicholas School of the Environment. When researchers actually analyze such products in the laboratory, they sometimes find PBDE levels that do not match what industry has told them to expect.
In recent months, other researchers have also reported that both older computers and televisions can be significant sources of the lightweight PBDEs associated with the commercial Penta formulation, which has been banned in Europe and discontinued in the U.S. since 2004. Researchers have known that older computer monitors can contain the Octa formulation, which also includes a small amount of the lighter PBDEs found in the Penta formulation. However, Harrad’s group conducted their tests with passive polyurethane-foam samplers, which are known to underestimate levels of the heavier PBDE compounds associated with the Octa formulation.
Rene Montaigne of the European Chemical Industry Council’s Brominated Flame Retardant Industry Panel acknowledges that the Penta formulation was previously used in printed circuit boards and microprocessor packaging. However, none of the researchers contacted for this article were aware of this use of Penta PBDEs.
The presence of these lighter PBDEs in older computers raises the question of whether their hot, volatile air emissions could contribute to the inexplicably large concentrations of PBDEs sometimes found in house dust, says Miriam Diamond, a professor at the University of Toronto. The findings suggest that by the time they are retired, such electronics could be a source of more toxic PBDEs than previously believed, she adds.
Harrad’s new paper also provides one of the first peer-reviewed reports of levels of PBDEs in cars. The paper shows that the levels varied by two orders of magnitude. The highest level of 8200 pg/m3 represents “the most contaminated microenvironment of all the homes, offices, public microenvironments, and cars studied,” Harrad says.
“Given that the average American spends a lot of time in their car, [which can] get pretty darn hot in the summer, cars might be an important source of PBDEs for some people,” points out Tom Webster of the Boston University School of Public Health’s environmental health department.
Although PCBs have been banned for more than 30 years, Harrad says that his paper—when considered together with other research—also suggests that some as-yet-unaccounted-for sources of these compounds may be present in newer homes. For example, the levels inside his 1994 home are more than 5 times the levels outside the home. —KELLYN S. BETTS
