Photochemical Decomposition of 15 Polybrominated Diphenyl Ether Congeners in Methanol/Water

Abstract

Among all brominated flame retardants in use, the polybrominated diphenyl ethers (PBDEs) have been identified as being of particular environmental concern due to their global distribution and bioaccumulating properties, as observed in humans and wildlife worldwide. Still there is a need for more data on the basic characteristics of PBDEs to better understand and describe their environmental fate. Hence, the aim of this study was to investigate the photochemical degradation of PBDEs with different degrees of bromination. The photochemical degradation of 15 individual PBDEs substituted with 4-10 bromine atoms was studied in methanol/water (8:2) by UV light in the sunlight region. Nine of these were also studied in pure methanol, and four of the nine PBDEs were studied in tetrahydrofuran. The photochemical reaction rate decreased with decreasing number of bromine substituents in the molecule but also in some cases influenced by the PBDE substitution pattern. The reaction rate was dependent on the solvent in such a way that the reaction rate in a methanol/water solution was consistently around 1.7 times lower than in pure methanol and 2-3 times lower than in THF. The UV degradation half-life of decaBDE (T1/2 = 0.5 h) was more than 500 times shorter than the environmentally abundant congener 2,2',4,4'-tetraBDE (T1/2 = 12 d) in methanol/water. The quantum yields in the methanol/water solution ranged from 0.1 to 0.3. The photochemical reaction of decaBDE is a consecutive debromination from ten- down to six-bromine-substituted PBDEs. Products with less than six bromines were tentatively identified as brominated dibenzofurans and traces of what was indicated as methoxylated brominated dibenzofurans.

Summer atmospheric polybrominated diphenyl ethers in urban and rural areas of northern China

“…Similar results have been reported previously (Harrad and Hunter, 2006;Hu et al, 2011). Longer half-life and higher volatility of BDE-47 compared to BDE-99 can be an important reason that BDE-99 to BDE-47 ratio in atmosphere was lower than those in commercial products (Eriksson et al, 2004). Relatively high ratios of BDE-17 (0.06), BDE-28 (0.56), and BDE-66 (0.31) to BDE-47 were also found in this study compared to the ratios of DE-71 (0.0018, 0.0065, 0.014) and Bromkal 70-5DE (0.0012, 0.0023, 0.0049) (La Guardia et al, 2006), because higher brominated PBDEs are less volatile (Watanabe and Sakai, 2003).…”

Aerosol-Mediated Transport and Deposition of Brominated Diphenyl Ethers to Antarctica

“…27 The photodegradation half-lives for the pentaBDE components decrease as follows: BDE100 > BDE47 > BDE99 indicating that BDE99 is the most photolabile of these three BDE congeners. 28,29 Therefore, the low level of BDE99/100 associated with the aerosol particles likely indicates that BDE99 is photodegraded during LRAT from source regions during the austral spring and summer when the air samples were collected. In Alert, Canada, the average ratio of BDE 99/100 was 5.4(±1.4) and 47/99 1.1(±0.26) (giving a ratio of 47/100 of ~5.9).…”

Investigation of PBDEs in Landfill Leachates from Across Canada

“…Some studies have demonstrated that BDE congeners can debrominate as a result of exposure to UV rays (Eriksson et al 2004;Söderström et al 2004). However, the decomposition products were not identified in these papers.…”