Photochemical Formation of Halogenated Dioxins from Hydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) and Chlorinated Derivatives (OH-PBCDEs)

Abstract

The potential photochemical formation of polybrominated and mixed halogenated dibenzo-p-dioxins (PBDDs and PXDDs) from hydroxylated polybrominated and polybrominated/ chlorinated diphenyl ethers (OH-PBDEs and OH-PBCDEs) in aqueous solution was studied. The ortho-hydroxylated BDE47 derivative 6-OH-BDE47, and chlorinated derivatives 3-Cl-6-OH-BDE47, 5-Cl-6-OH-BDE47, and 3,5-Cl-6-OH-BDE47 were photolyzed under sunlight at 45 degrees N latitude in buffered waters, Mississippi River water, Lake Josephine water, and ultrapure water adjusted to the pH of the natural waters. Chemical actinometry was used to determine reactant quantum yields which were calculated to be between 0.03 and 0.21, with lower yields for the chlorinated derivatives under all conditions. Quantum yields under natural water conditions were not significantly enhanced indicating that direct photolysis is the primary process of photochemical degradation. The formation of halogenated dioxins from the outdoor photolysis of the four OH-PBDEs/OH-PBCDEs under all conditions was confirmed. Dioxin yields of 0.7-3.6% were found, with higher yields for 6-OH-BDE47 under all conditions. This study suggests that photolysis of OH-PBDEs and OH-PBCDEs is a potential formation pathway of PBDDs and PXDDs in the environment.

Theoretical Investigation on Mechanistic and Kinetic Transformation of 2,2′,4,4′,5-Pentabromodiphenyl Ether

“…Addition of the other ring to ortho-C atoms was much easier, but the favored pathway was the one toward IM40 because this pathway exhibited the lowest In addition to the aforementioned reactions, PBDDs can form through the decomposition of ortho-position OH-PBDEs, as confirmed both experimentally 60 and theoretically. Figure S8 of the Supporting Information depicts the mechanism of PBDDs resulting from four ortho-OH-PBDEs which has been verified experimentally 49 and theoretically. 40,50 Removal of phenoxyl hydrogen atoms led to essential intermediates, which were precursors of PBDDs.…”

Powerful GC-TOF-MS Techniques for Screening, Identification and Quantification of Halogenated Natural Products

“…15) Similarly, two natural formation routes for PBDDs have been proposed enzymatic (bromoperoxidase) dimerization of BPs 16) and photolytic cyclization of OH-PBDEs. 17,18) There are also anthropogenic sources of PBDDs and PBDFs, 19) but the absence of PBDFs in the samples indicated that PBDDs were of natural origin. The same may then be true for the OH-tetraBDD.…”

Brominated phenols, anisoles, and dioxins present in blue mussels from the Swedish coastline

“…Such enzymatic formation, catalyzed by haloperoxidase, has been proposed to account for the chlorinated analogues (PCDDs) present in forest soil (Hoekstra et al 1999). In addition, OH-PBDEs may be transformed to PBDDs photochemically (Steen et al 2009) and, hypothetically, enzymatically in vivo (Gribble 2000).…”