DBDE breaks down to lower brominated congeners (nona- to hexa-BDEs) with a half-life of < 15 min in toluene and approximately 15, 100, and 200 hr in sand, sediment, and soil, respectively (Tysklind et al.
In contrast, point sources releasing DBDE have resulted in sediment with concentrations as high as 5 mg/kg.
Whether these are due to debromination of BDE 209, as suggested by the studies involving exposure of trout to a commercial DBDE mixture (Kierkegaard et al.
PentaBDE is more toxic than OBDE, whereas DBDE is essentially nontoxic to invertebrates.
National Toxicology Program (NTP) conducted 2-year feeding studies with DBDE (NTP 1986) and showed that high doses up to 50,000 ppm in the diet (5,000 g/kg/day) resulted in neoplastic nodules in the liver in both male and female rats; nodules were also apparent in male rats given a low dose (25,000 ppm).