Polybrominated diphenyl ether (PBDE) flame retardants degrade in natural sunlight and could be producing significant amounts of toxic compounds in household dust and the environment, according to Natsuko Kajiwara and coworkers of Japan’s National Institute for Environmental Studies (Environ. Sci. Technol., DOI: 10.1021/es800060j). PBDEs, which are used to protect flammable polymers, may cause health problems during fetal development and could be toxic to the liver and the nervous system. The researchers found that decabromodiphenyl ether compounded into a pulverized polystyrene matrix had a half-life of 51 days when exposed to sunlight. Photodegradation products included hexa-, octa-, and nona-brominated diphenyl ethers, as well as polybrominated dibenzofurans. Samples of used television casings showed similar degradation products. But samples of an alternative flame retardant, decabromodiphenyl ethane, mixed with polystyrene showed no degradation. The study’s results suggest that risk assessment of products incorporating PBDEs should include evaluating photodegradation products produced during normal use as well as during disposal and recycling processes, the authors conclude.