Increased cell numbers improve marine biodegradation tests for persistence assessment.

Area of Science:

• Environmental Science
• Microbiology
• Chemical Safety

Background:

• Standard OECD biodegradation screening tests (BSTs) are often too short and variable for accurate persistence assessment.
• Existing BSTs can lead to false negatives, misclassifying persistent chemicals as non-persistent.

Purpose of the Study:

• To develop and validate an environmentally relevant biodegradation screening test (erBST) for marine environments.
• To improve the accuracy and reduce variability in assessing chemical persistence in marine settings.

Main Methods:

• Extended test durations beyond 28 days and increased marine biomass concentrations (100-fold) using tangential flow filtration.
• Validated the marine erBST against a standard BST using five 14C-labeled reference compounds with varying biodegradation potentials.
• Conducted a full mass balance to track chemical fate during the tests, modified from OECD 301B.

Main Results:

• The erBST demonstrated higher accuracy and lower variability than the standard BST in classifying chemicals as non-persistent or potentially persistent.
• erBST correctly classified 60% of replicates according to REACH non-persistence criteria (≥60% biodegradation in 60 days), with a 21% coefficient of variation.
• Standard BST correctly classified 40% of chemicals with a 36% coefficient of variation; all non-persistent chemicals degraded better in erBST.

Conclusions:

• The environmentally relevant biodegradation screening test (erBST) is a more reliable method for assessing marine chemical persistence.
• Further inter-laboratory validation with diverse seawater sources is recommended to confirm the erBST's variability and reliability.