Multi-laboratory Validation of a New Marine Biodegradation Screening Test for Chemical Persistence Assessment.

Current biodegradation screening tests are not specifically designed for persistence assessment of chemicals, often show high inter- and intra-test variability, and often give false negative biodegradation results. Based on previous studies and recommendations, an international ring test involving 13 laboratories validated a new test method for marine biodegradation with a focus on improving the reliability of screening to determine the environmental degradation potential of chemicals. The new method incorporated increased bacterial cell concentrations to better represent the microbial diversity; a chemical is likely to be exposed in the sampled environments and ran beyond 60 days, which is the half-life threshold for chemical persistence in the marine environment. The new test provided a more reliable and less variable characterization of the biodegradation behavior of five reference chemicals (sodium benzoate, triethanolamine, 4-nitrophenol, anionic polyacrylamide, and pentachlorophenol), with respect to REACH and OSPAR persistence thresholds, than the current OECD 306 test. The proposed new method provides a cost-effective screening test for non-persistence that could streamline chemical regulation and reduce the cost and animal welfare implications of further higher tier testing.

Improving the biodegradability in seawater test (OECD 306).

Growth and extensive urbanisation of the human population has been accompanied by increased manufacture and use of chemical compounds. To classify the fate and behaviour of these compounds in the environment, a series of international standardised biodegradation screening tests (BSTs) were developed over 30 years ago. In recent years, regulatory emphasis (e.g. REACH) has shifted from measuring biodegradation towards prioritisations based on chemical persistence. In their current guise, BSTs are ineffective as screens for persistence. The marine BST OECD 306 in particular is prone to high levels of variation and produces a large number of fails, many of which can be considered false negatives. An ECETOC funded two-day workshop of academia, industry and regulatory bodies was held in 2015 to discuss improvements to the marine BSTs based on previous research findings from the Cefic LRI ECO11 project and other foregoing studies. During this workshop, methodological improvements to the OECD 306 test were discussed, in addition to clarifying guidance on testing and interpretation of results obtained from marine BSTs (such as pass criteria, lag phases, freshwater read across and complex substances). Methodologically: (i) increasing bacterial cell concentrations to better represent the bacterial diversity inherent in the sampled environments; and (ii) increasing test durations to investigate extended lag phases observed in marine assessments, were recommended to be validated in a multi-institutional ring test.