The 3Rs in whole-effluent toxicity testing, a Canadian perspective

Across the world, there is an increasing desire for the replacement of whole-organism toxicity tests with new approach methods (NAMs) that refine, reduce, and replace animal use. These principles, collectively known as the 3Rs, are critical to consider when discussing NAM development and implementation. Despite the frequency at which NAMs are discussed as replacements to existing toxicity test methods, the application to whole-effluent toxicity (WET) monitoring is largely ignored in favour of their use for chemical assessments. These WET test methods are an ideal receptor for NAMs due to their volume of use and highly repetitive nature as legislative tools used in many areas of the world. In this paper, we investigate this with a focus on Canadian effluent regulation, first discussing the current tools used to regulate effluent toxicity in Canada and how NAMs can aim to fill these roles rapidly to address the changing landscape of Canada's policy on vertebrate use in toxicity testing. We discuss three NAMs being developed with potential to be applied to whole-effluent toxicity testing, summarizing current trends in the literature, and identify areas where they may struggle to may struggle to meet the needs of environmental regulations. Further research needs are highlighted. Finally, we propose ways to integrate these NAMs into environmental regulations to robustly evaluate effluent toxicity should future data should future data collected for effluents follow existing trends.