||A GC-ECNI/MS method was used to measure the levels of twenty-one PBDE congeners in the dust sampled from 66 personal automobiles. The dominant congener found in personal automobile dust was BDE-209 comprising 82% of the total PBDE levels with a median level of 8.1 μg g -1 . Statistical analysis of the automobile attributes indicates that BDE-209 levels are different ( p < 0.05) with respect to groupings by automobile model year, automobile manufacturer, and the country of manufacture. Automobile dust samples contained the characteristic percentages of the PBDE congeners that comprise the commercial penta-BDE and deca-BDE formulations. A photochemical irradiator was constructed to monitor the photodegradation of PBDEs in dust in automobiles. Photodegradation was not observed in the automotive dust samples; however, photodegradation was observed on the surface of solid sodium sulfate crystals spiked with BDE-209. A mechanism for the photochemical transformations of BDE-209 to lower congeners was proposed. Exposure calculations estimate the adult and child median total PBDE daily intakes from automobile dust at 9.6 and 16.9 ng day -1 , respectively. Median concentration of PBDEs on personal automobile dust is approximately five times more than concentrations reported on indoor dust. Even though the average time spent in an automobile is much less than in an indoor environment, the higher concentrations found in automotive dust could represent a significant and unaccounted for exposure source via inhalation or ingestion.