Chapter 9

In vitro assays for the risk assessment of chemicals

Explain the difference of a specifically and a selectively acting chemical in an in vitro assay using the specificity ratios SRcytotoxicity and the SRbaseline.

In the Excel sheet “9A2 Exercise TR” you find algal toxicity data from Glauch and Escher (2020), 10.1002/etc.4873. You can find the experimentally determined EC1024h, growth and the QSAR EC1024h, growth values of several test chemicals in the combined algae test.

a)    Please calculate the toxic ratio (TR24h, growth) for all chemicals.

b)    Decide whether the chemical is a baseline toxicant or showing specific toxicity based on these results.

9A2Exercise TR.xlsx

Can we directly implement in vitro bioassays in chemical risk assessment by replacing animal testing or is there more to it? In vitro assays serve as animal alternatives for risk assessment but their implementation in legal frameworks appears very slow. What prevents the paradigm shift from in vivo to in vitro testing for chemical safety assessment?