Screening for Chemical Compliance in Water Quality Monitoring with In Vitro Bioassays

Abstract Bioassays have proven their use in water quality monitoring. This study presents a novel framework for deploying bioassays to enable compliance screening in relation to regulatory threshold values. Bioanalytical equivalent concentrations for chemicals are derived from bioactivity data to calculate for each bioassay response the Bioanalytical Risk Quotient percentage (BRQ%): the percentage of chemicals potentially surpassing their quality standard (QS). If the bioassay response indicates BRQ0, none of the individual chemicals with known bioactivity in the bioassay surpass their QS. Should the bioassay response indicate potential QS exceedance by some candidates, the magnitude of that exceedance is a guide to prioritize chemicals for confirmation by instrumental analyses. Multiple bioassays are required to cover compliance for all relevant chemicals. As a proof of concept, compliance with the Dutch Drinking Water Regulation was evaluated for 100 surface water monitoring events by derivation of BRQ% values for a battery of six bioassays. Full compliance could not be guaranteed for any of the water samples, with a median potential noncompliance for 13% of chemicals. The presented framework has potential for broader application, such as compliance testing related to QS for human health or the environment in a variety of matrices or for specific permits.