California residents may experience the highest polybrominated diphenyl ether (PBDE) flame retardant exposures in the United States, the nation with the highest body burdens worldwide. It is hypothesized that Californians' high exposures are due to the state's strict furniture flammability standards. Ingestion of PBDE-contaminated dust, to which children may be particularly susceptible, is a dominant exposure pathway. Low-income populations may also face disparately high exposures due to the presence of older, deteriorated or poorly manufactured furniture treated with PBDEs. We collected up to two dust samples per home (54 samples total), several days apart, from low-income California households in the urban community of Oakland (n=13 homes) and the agricultural community of Salinas (n=15 homes). We measured BDE-47, BDE-99 and BDE-100, the major constituents of the penta-PBDE flame retardant formulation commonly used in furniture. All three PBDE congeners were detected in every sample with concentrations (loadings) ranging from 185 to 126,000ng/g (621-264,000ng/m(2)), 367-220,000ng/g (1550-457,000ng/m(2)), and 84-41,100ng/g (257-85,700ng/m(2)) for BDE-47, BDE-99 and BDE-100, respectively. Median concentrations (loadings) observed in Salinas homes for BDE-47, BDE-99 and BDE-100 were 3100ng/g (10,800ng/m(2)), 5480ng/g (19,500ng/m(2)), and 1060ng/g (3810ng/m(2)), respectively, and in Oakland homes 2780ng/g (10,700ng/m(2)), 4450ng/g (19,100ng/m(2)), and 1050ng/g (4000ng/m(2)), respectively. Maximum concentrations for BDE-47 and BDE-99 are the highest reported to date. Indoor concentrations and loadings did not significantly differ between communities; concentrations and loadings were strongly correlated between collections for all three congeners (Spearman rho=0.79-0.97, p<0.002). We estimated non-dietary ingestion of each congener for one child in each home (n=28 children) and found that estimated intake for BDE-47 and BDE-99 exceeded the U.S. Environmental Protection Agency's recommended chronic reference dose for three and five children, respectively. Children's estimated intake via dust ranged from 1.0 to 599ng/kg/day, 2.0-1065ng/kg/day and 0.5-196ng/kg/day for BDE-47, BDE-99 and BDE-100, respectively. In order to mitigate these exposures, future research must address the factors that contribute to PBDE exposures in low-income homes.
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