Extrapolation factors for calculating ecotoxicity effects in LCA

Journal article, 2024

Purpose: This study focuses on updating, improving, and expanding the extrapolation factors needed to convert various acute or chronic effect concentration indicators into consistent chronic EC10eq (effect concentration inducing a 10% response over background) for use in life cycle assessment (LCA). Our main objectives include (1) to present a detailed approach for the harmonization of ecotoxicity data, with a focus on deriving extrapolation factors, and (2) to estimate both generic and species group-specific extrapolation factors, facilitating the conversion of effect concentration indicator groups (EC10eq and EC50eq) into chronic EC10eq. Methods: Experimental ecotoxicity data were sourced from CompTox Version 2.1.1, which integrates toxicity information from ToxValDB v9.1.1, and the information from REACH registration dossiers. We developed a framework for harmonizing ecotoxicity data, ensuring uniformity and high quality of aquatic ecotoxicity information from these sources. Through linear regression analysis, both generic and species group-specific extrapolation factors were then derived. Results and discussion: Harmonization of ecotoxicity data yielded a streamlined dataset with 339,729 datapoints for 10,668 chemicals, reflecting a 54% reduction in raw datapoints. The geometric mean-based aggregation process produced 79,001 aggregated effect concentration datapoints at the species level, 41,303 at the species group level, and 23,215 at the effect concentration indicator level for these chemicals. This process facilitated the derivation of 3 generic and 24 species group-specific extrapolation factors, allowing for the conversion of effect concentration indicator groups (EC10eq and EC50eq) to a chronic EC10eq across two exposure classes (acute vs. chronic) and species groups, as defined in the US EPA ECOTOX knowledgebase, including algae, amphibians, fish, crustaceans, insects/spiders, invertebrates, molluscs, and worms. Conclusions: The harmonization of ecotoxicity data and the derived extrapolation factors permit the integration of diverse datapoints with varying effect concentration indicators and exposure durations into USEtox ecotoxicity characterization factors. This has the potential to enhance substance coverage for characterizing ecotoxicity effects across chemicals in LCA frameworks by permitting wider species coverage. More generally, this is part of global efforts to extend the potential for quantitative assessment of environmental impacts of chemicals in an LCA framework.