Polybrominated diphenyl ethers: Occurrence, dietary exposure, and toxicology

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in plas tics (concentration, 5-30%) and in textile coatings. Commercial products co nsist predominantly of penta-, octa-, and decabromodiphenyl ether mixtures, and global PBDE production is about 40,000 tons per year. PBDEs are bioacc umulated and biomagnified in the environment, and comparatively high levels are often found in aquatic biotopes from different parts of the world. Dur ing the mid-1970-1980s there was a substantial increase in the PBDE levers with time in both sediments and aquatic biota, whereas the latest Swedish d ata (pike and guillemot egg) may indicate that levels are at steady state o r are decreasing. However, exponentially increasing PBDE levels have been o bserved in mother's milk during 1972-1997. Based on levels in food from 199 9, the dietary intake of PBDE in Sweden has been estimated to be 0.05 mug p er day. Characteristic end points of animal toxicity are hepatotoxicity, em bryotoxicity, and thyroid effects as well as maternal toxicity during gesta tion. Recently, behavioral effects have been observed in mice on administra tion of PBDEs during a critical period after birth. Based on the critical e ffects reported in available studies, we consider the lowest-observed-adver se-effect level (LOAEL) value of the PBDE group to be 1 mg/kg/day (primaril y based on effects of pentaBDEs). In conclusion, with the scientific knowle dge of today and based on Nordic intake data, the possible consumer health risk from PBDEs appears limited, as a factor of over 10(6) separates the es timated present mean dietary intake from the suggested LOAEL value. However , the presence of many and important data gaps, including those in carcinog enicity, reproduction, and developmental toxicity, as well as additional ro utes of exposure, make this conclusion only preliminary. Moreover, the time trend of PBDEs in human breast milk is alarming for the future.