Women in the San Francisco Bay Area have three to 10 times the amount of a dangerous persistent organic pollutant in their breast tissue as do either European or Japanese women, according to a study released yesterday in the journal Environmental Health Perspectives. Polybrominated diphenyl ethers (PBDEs) are flame retardants commonly used in foam, textiles, and plastic electronic casings; they have been shown to mimic hormones, cause thyroid problems, and delay neurological development. The level of PBDEs in both humans and wildlife worldwide has been increasing over the past decade. Most exposure to PBDEs occurs when people inhale dust from consumer products treated with the chemicals, according to the study authors. Scientists are now exploring whether the heightened level of PBDEs found in the Bay Area correlates to unusually high breast cancer rates in the region.