Rapid breakdown of brominated flame retardants by soil microorganisms

Abstract

Polybrominated diphenyl ethers (PBDEs) have been extensively and successfully used as fire retardants in a multitude of products. However, due to their aromatic components and toxicological properties, they are assumed to be persistent environmental pollutants and a popularly-used commercial mixture, DE-71, has been removed from American and European marketplaces. However, our current work shows mixed bacterial cultures, derived or extracted from soils experimentally contaminated with DE-71, were capable of utilizing these as a sole carbon source. Most notably, almost complete loss of parent compounds takes place within a few minutes. Determining pathways was hindered by both the speed of the microbial degradation and the low water solubility of the congeners, complicating detection. The bacterial enrichment communities have been characterized using DGGE analysis and DNA sequencing. Element-specific detection was coupled to ion chromatography and only one degradation product detectable by ICP-MS, the bromide ion, was found. Additionally, samples were analyzed by GC/TOF-MS using a mass-defect-based digital noise filtering technique to facilitate observation of bromine-containing unknowns and ESI-MS was used to identify the non-volatile brominated unknown peaks. However, low concentrations (100 μg L⁻¹ initial fortification and substantially lower levels of theorized by-products) prohibited successful compound identification.