Monohydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) and Dihydroxylated Polybrominated Biphenyls (Di-OH-PBBs): Novel Photoproducts of 2,6-Dibromophenol

Abstract

Hydroxylated polybromodiphenyl ethers (OH-PBDEs) are emerging aquatic pollutants, but their origins in the environment are not fully understood. There is evidence that OH-PBDEs are formed from bromophenols, but the underlying transformation processes remain unknown. Here we investigate if the photoformation of OH-PBDEs from 2,6-dibromophenol in aqueous solution involves 2,6-bromophenoxyl radicals. After UV irradiation of an aqueous 2,6-dibromophenol solution, HPLC-LTQ-Orbitrap MS and GC/MS analysis revealed the formation of a OH-PBDE and a dihydroxylated polybrominated biphenyl (di-OH-PBB). Both dimeric photoproducts were tentatively identified as 4′-OH-BDE73 and 4,4′-di-OH-PBB80. In addition, three debromination products (4-OH-BDE34, 4′-OH-BDE27, and 4,4′-di-OH-PBBs) were observed. Electron paramagnetic resonance spectroscopy revealed the presence of a 2,6-dibromophenoxyl radical with a six-line spectrum (aH (2 meta) = 3.45 G, aH (1 para) = 1.04 G, g = 2.0046) during irradiation of a 2,6-dibromophenol solution in water. The 2,6-dibromophenoxyl radical had a relatively long half-life (122 ± 5 μs) according to laser flash photolysis experiments. The para-para C-C and O-para-C couplings of these 2,6-dibromophenoxyl radicals are consistent with the observed formation of both dimeric OH-PBDE and di-OH-PBB photoproducts. These findings show that bromophenoxyl radical-mediated phototransformation of bromophenols is a source of OH-PBDEs and di-OH-PBBs in aqueous environments that requires further attention.

Oxidation Kinetics of Bromophenols by Nonradical Activation of Peroxydisulfate in the Presence of Carbon Nanotube and Formation of Brominated Polymeric Products

“…On the oxidative treatment of BrPs, the formation of brominated polymeric products, such as hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and hydroxylated polybrominated biphenyls (OH-PBBs), becomes an important issue. Several studies have reported that OH-PBDEs and/or OH-PBBs can be appreciably generated from precursor BrPs when treated by Mn­(VII), naturally occurring manganese oxides, photolysis, , or enzymes-mediated oxidation. , These brominated polymeric products have altered or enhanced toxicological effects (e.g., disruption to thyroid hormone homeostasis, disruption to sex hormone steroidogenesis, and neurotoxicity) in comparison to parent compounds, − and hence, their occurrence in natural environments and engineered processes has raised great concerns.…”

Carcinogenic activity of pentabrominated diphenyl ether mixture (DE-71) in rats and mice

“…Recent studies suggest that marine bacteria can synthesis PBDEs using flavin-dependent brominases [ 19 ]. Another source of PBDEs could be photodegradation of bromophenols [ 20 ]. Oral, dermal, and inhalation exposure are all possible routes of PBDE exposure [ 21 ].…”

Comparison of the oxidation of halogenated phenols in UV/PDS and UV/H2O2 advanced oxidation processes

“…BA was employed to carry out the competition kinetics experiments due to its negligible photolysis under UV irradiation, and TBA was employed to quench HOc in the UV/PDS process to obtain single SO 4 c À oxidation. The second-order reaction rate constants of BPs with SO 4 c À and HOc were calculated via eqn (2) and 3; here, the second-order reaction rate constants of BA with SO 4 c À (k SO 4 c À ,BA ) and HOc (k OHc,BA ) were reported to be 1.20 Â 10 9 M À1 s À1 and 5.90 Â 10 9 M À1 s À1 , respectively. 27…”

“…Halogenated phenols (HPs) are typical halogenated compounds that have received increasing attention in recent years due to their potential hazards to water environments and human health. 1,2 Halogenated compounds have been widely used as brominated ame retardants, refrigerants, preservatives, etc. 3,4 With the high production and usage of halogenated compounds, large amounts of HPs (e.g., bromophenols (BPs) and chlorophenols (CPs)) are released from those compounds and discharged into water environments.…”