Abstract
Comprehensive assessment of environmental biodegradability of pollutants is limited by the use of low throughput systems. These are epitomized by the Organisation for Economic Cooperation and Development (OECD) Ready Biodegradability Tests (RBTs), where one sample from an environment may be used to assess a chemical's ability to readily biodegrade or persist universally in that environment. This neglects the considerable spatial and temporal microbial variation inherent in any environment. Inaccurate designations of biodegradability or persistence can occur as a result. RBTs are central in assessing the biodegradation fate of chemicals and inferring exposure concentrations in environmental risk assessments. We developed a colorimetric assay for the reliable quantification of suitable aromatic compounds in a high throughput biodegradation screening test (HT-BST). The HT-BST accurately differentiated and prioritized a range of structurally diverse aromatic compounds on the basis of their assigned relative biodegradabilities and quantitative structure-activity relationship (QSAR) model outputs. Approximately 20 000 individual biodegradation tests were performed, returning analogous results to conventional RBTs. The effect of substituent group structure and position on biodegradation potential demonstrated a significant correlation (P < 0.05) with Hammett's constant for substituents on position 3 of the phenol ring. The HT-BST may facilitate the rapid screening of 100 000 chemicals reportedly manufactured in Europe and reduce the need for higher-tier fate and effects tests.
Highlights
Microbial biodegradation, which can determine the fate and burden of anthropogenic organic chemicals in the environment, is an important but poorly predictable process
The chemical concentrations determined using the 4-nitrobenezediazonium tetrafluoroborate (4-NBTFB) colorimetric assay were not significantly different from those obtained by HPLC when used to quantify the parent compound in two high throughput biodegradation screening test (HT-biodegradation screening tests (BST)) showing partial degradation (ANOVA; P = 0.992 and P = 0.560)
The HT-BST described here, using a single activated sludge source of inoculum, has been shown to correctly prioritize a group of structurally diverse aromatic chemicals based on their previous biodegradability classifications using conventional Ready Biodegradability Tests (RBTs) test criteria
Summary
Microbial biodegradation, which can determine the fate and burden of anthropogenic organic chemicals in the environment, is an important but poorly predictable process. Comprehensive assessment of biodegradation in the environment is limited by the use of low throughput “one sample-one test” systems that neglect the considerable structural and functional diversity inherent in natural microbial communities Such tests are epitomized by the OECD (Organisation for Economic Co-operation and Development) 301 Ready Biodegradability Tests (RBTs)[1] that assess aerobic biodegradation in aqueous media, for which an inoculum of activated sludge is widely used.[2] They are at the forefront of international regulatory screening of manufactured chemicals, which number 100 000-plus in Europe alone.[3] The hazards of up to 90% of these chemicals are unknown.[4] The European registration, evaluation, authorization, and restriction of chemicals (REACH) directive was introduced to streamline chemical legislation[5] and advocates the prioritization of chemicals based on hazards, including their ability to persist in the environment. Are RBTs low throughput, but they lack replication and are notoriously
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