Results of an international interlaboratory study on dioxin-like activities in drinking-, river surface- and wastewater using DR CALUX bioassay

Aquatic animals and consumers of aquatic animals are exposed to increasingly complex mixtures of known and as -yet -unknown chemicals with dioxin -like toxicities in the water cycle. Effect- and cell -based bioanalysis can cover known and yet unknown dioxin and dioxin -like compounds as well as complex mixtures thereof but need to be standardized and integrated into international guidelines for environmental testing. In an international laboratory testing (ILT) following ISO/CD 24295 as standard procedure for rat cell -based DR CALUX un-spiked and spiked extracts of drinking-, surface-, and wastewater were validated to generate precision data for the development of the full ISO -standard. We found acceptable repeatability and reproducibility ranges below 36 % by DR CALUX bioassay for the tested un-spiked and spiked water of different origins. The presence of 17 PCDD/ Fs and 12 dioxin -like PCBs was also confirmed by congener -specific GC-HRMS analysis. We compared the sum of dioxin -like activity levels measured by DR CALUX bioassay (expressed in 2,3,7,8-TCDD Bioanalytical Equivalents, BEQ; ISO 23196, 2022) with the obtained GC-HRMS chemical analysis results converted to toxic equivalents (TEQ; van den Berg et al., 2013).