Temporal trends in concentrations of legacy and novel brominated flame retardants in house dust from Birmingham in the United Kingdom

Concentrations of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), tetrabromobisphenol-A (TBBPA) and two potential replacements decabromodiphenylethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) were measured in dust samples collected from 14 homes across Birmingham (UK). Concentrations were compared with those from the same city in previous studies to ascertain any temporal changes and to assess the effects of legislative restrictions. The average ∑HBCDDs concentration (46,000 ng/g; median = 280 ng/g) included the highest dust concentration recorded globally (570,000 ng/g). This is despite the listing of HBCDD under the Stockholm Convention in 2013, demonstrating that decreases in indoor contamination will likely be slow as existing sources are gradually discarded. In contrast, concentrations of BDE-47 (mean = 5.7 ng/g; median = 0.93 ng/g) and BDE-99 (mean = 11 ng/g; median = 2.9 ng/g) were significantly lower than in all previous (p < 0.01) studies in the same city since 2006, suggesting restrictions on the Penta-BDE formulation have been effective. The average BDE-209 concentration (4800 ng/g; median = 1600 ng/g) is lower than the peak average concentration, which was observed in 2007 (280,000 ng/g), however this is not a significant decline, probably due to the later imposition of Deca-BDE restrictions compared to those on Penta-BDE. Decreases in PBDE concentrations have coincided with a significant (p < 0.01) increase in DBDPE concentrations (average = 1500 ng/g; median = 660 ng/g) since 2014, suggesting its use as a replacement flame retardant for Deca-BDE. While no significant change was detected for BTBPE (average 11 ng/g; median = 0.84 ng/g in this study); concentrations of TBBPA (average = 34 ng/g; median = 35 ng/g) were significantly lower (p < 0.05) than in 2007 (average 62 ng/g). The decreases observed in PBDE concentrations, demonstrates that legislation has been effective in reducing the commercial use of PBDEs, however this has coincided with increases of alternative flame retardants such as DBDPE.