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

Abstract

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 our understanding of the environmental persistence of chemicals

“…The main changes were that the proposed improved method incorporated increased bacterial cell numbers and ran beyond 60 days. The methods were considered to better represent the microbial diversity inherent in the sampled environments and, based on the biodegradation behavior of five reference chemicals, the new method is considered to be a more reliable and less variable method for assessing marine biodegradability (Ott et al, 2020 ).…”

“… Abbreviations: EU REACH, European Union Registration, Evaluation, Authorisation and Restriction of Chemicals; OECD, Organisation for Economic Co‐operation and Development; UVCB, substances of unknown or variable composition, complex reaction products, or biological materials. a As the workshop reference in March 2020 OSPAR has accepted the recommendations made by Ott et al ( 2020 ) regarding biomass concentration for chemical persistence assessment B. Rowles, Cefas, personal communication. …”

“… a As the workshop reference in March 2020 OSPAR has accepted the recommendations made by Ott et al ( 2020 ) regarding biomass concentration for chemical persistence assessment B. Rowles, Cefas, personal communication. …”

Influence of short- and long-term exposure on the biodegradation capacity of activated sludge microbial communities in ready biodegradability tests

“…It has been shown that a low test volume could increase the lag phase period and the chance of false negatives, due to the lower transferred biomass and therefore a lower chance to introduce competent degraders. [49][50][51][52][53] This "biodegradation lottery" is well known and several solutions, such as increasing the inoculum density 20,21 or the test volume 12 has been proposed. In the present study, pre-exposing the inocula reduced the MET biodegradation variation and thus reduced the effect of the biodegradation lottery.…”

“…Multiple methods have been proposed to improve current ready biodegradability testing protocols with the aim to lower the number of false negatives and test variability, without having an impact on the probability of a false positive result. These methods include i) pre-exposure, 9,14,19 ii) increasing the inoculum density, 20,21 iii) increasing the test duration 14,20 and iv) increasing the volume of test flasks. 18,22 Pre-exposure, at test concentration, is thought to reduce the differences between inocula caused by their differing origins and to reduce the differences in lag phases at the start of the test.…”