News Coverage
Deca PBDE flame retardant gets around
Published January 8, 2004
An analysis of the organic film that adheres to windows recently published in Environmental Science & Technology reveals surprisingly high levels of the Deca polybrominated diphenyl ether (PBDE) flame retardant. Because the sum of all the PBDEs measured in the films was up to 63 times higher than the levels of PCBs on every sampled window, the study's authors say the films may foretell a continuing rise in PBDE levels.
The paper's lead author, Miriam Diamond of the University of Toronto's geography department, has become well known for her research into the toxins that adhere to impervious surfaces like sidewalks, roads, and windows. She believes that the greasy film on windows-an 11-100-nanometer-thick coating that she sometimes refers to as "window goo"-has potential to be used as a cost-effective method for monitoring air pollutants. "These grimy layers trap more than what you would suspect," Diamond says.
Diamond's research team most recently measured the concentrations of 41 individual PBDE compounds, or congeners, on windows in residential and commercial buildings in and around Toronto. The team found that brominated diphenyl ether-209 (BDE-209), the major component of the Deca brominated flame retardant mixture used in electronics equipment and on some textiles, dominated the mixtures of PBDEs. BDE-209 represented nearly 60% of the 14 PBDEs measured in significant quantities in outdoor window films and almost 50% of those PBDEs on the insides of the windows, according to the researchers' normalized calculations. The paper is one of several recent articles suggesting that Deca is widely present in the environment (Environ. Sci. Technol. 2004, 38, 8A-9A).
"Up to now, most studies on PBDEs have focused on the lower molecular weight congeners of the Penta formulation, primarily because these are abundant in the gas phase and are believed to be the most susceptible to long-range transport. BDE-209 is extremely involatile and will exist in the atmosphere almost entirely associated with particles," says Tom Harner, a research scientist with Environment Canada, the country's environmental protection agency. "Somehow the BDE-209 particles are making it into the atmosphere and moving around.. We need to better understand the fate and transport of particle-associated chemicals such as BDE-209," he adds.
The Deca flame retardant mixture is under increasing scrutiny, in part because the main North American manufacturer of the other two PBDE mixtures used to protect consumer goods, Penta and Octa, agreed to voluntarily discontinue those mixtures last November (Environ. Sci. Technol. 2004, 38, 14A). The Penta and Octa mixtures are slated to be banned in Europe and California.
"The observation of BDE-209 dominating the PBDE congeners present seems at odds with industry dogma that Deca does not escape finished products readily," says Rob Hale of the Virginia Institute of Marine Science. "This finding is in agreement with the high levels in house dust, however," he adds (Environ. Sci. Technol. 2003, 37, 407A-411A.)
The University of Toronto researchers' finding that the total PBDE concentrations were higher than the PCBs measured in every study sample is notable because almost all studies of the two compounds in the environment show that PCB levels are much higher, according to the Toronto researchers. Because window films respond more quickly to contaminant increases than biota like animals that concentrate toxins in their fat over time, the results can be interpreted as a sort of early warning of rapidly rising PBDE levels, they say.
In the Toronto study, the levels of PBDEs in films on indoor windows were up to 20 times greater than on outdoor windows. This level indicates that, like other semivolatile chemicals, PBDEs in indoor air serve as a significant source of the PBDEs in the regional environment.
"The high levels in indoor air certainly could impact human exposure," says Linda Birnbaum, director of the Experimental Toxicology Division of the U.S. EPA's National Health and Environmental Effects Research Laboratory. She says that her as-yet-unpublished studies of the PBDE levels in foods indicates that air could be an important exposure source.
"It is not a surprise to find that concentrations of Deca PBDE are higher indoors than out. All available evidence points to common household products as the chief source of these contaminants," says Sonya Lunder, an environmental analyst with the Environmental Working Group, a nonprofit group.
"Our research has documented PBDEs in similar levels of PBDEs in lipid of fish from the highly industrialized San Francisco Bay and from the bodies of 20 U.S. mothers (range 300 to 200 parts per billion in fish and 10 to 1000 parts per billion in mother's milk), meaning that our homes are just as contaminated as industrial waters."
Rain is likely to wash a large portion of the BDE-209 captured in the outdoor window films into urban surface waters, according to the Toronto researchers. The paper reveals an important source of the PBDEs in aquatic ecosystems, says Michael Ikonomou, a research scientist with Fisheries and Oceans Canada and a paper coauthor who has documented high levels of PBDEs in fish from pristine areas (Environ. Sci. Technol. 2003, 37, 240A-241A).
The researchers postulate that they found higher percentages of BDE-209 in films on outdoor windows than indoor films because of the higher rate of chemical degradation in films exposed to the elements. This chemical degradation would deplete the lighter congeners, they explain.
The paper also suggests that the heavier PBDEs may be debrominated to create lighter PBDEs. "The high concentration of BDE-209 may indicate a steady-state situation between inputs (from source) and outputs via photolytic debromination and volatilization of the resulting lower brominated, higher vapor pressure congeners, and wash-off of heavier compounds to surface waters," Diamond says.
However, the paper does not shed any light on the key question of which lighter PBDE compounds the BDE-209 breakdown may be generating, which could reveal whether the Deca formulation is the source of compounds like BDE-99 that are found throughout the globe and known to bioaccumulate.