Introducing FACTdb: A comprehensive database of Fish Acute Cell Toxicity

Pre-Print for the submitted Publication "Introducing FACTdb: A comprehensive database of Fish Acute Cell Toxicity" (currently under revision for minor revisions). Abstract: Fish acute toxicity can be assessed without animal testing using the RTgill-W1 assay, which was adopted in 2021 as OECD Test Guideline (TG) 249, constituting the first cell-based TG for ecotoxicity testing. While this advancement has led to an increase in publicly available acute fish cell line assay data, results remain dispersed across individual studies and often deviate from the TG. Consequently, defining the chemical coverage and applicability domain remains a challenge. To address this gap, we developed the Fish Acute Cell Toxicity database (FACTdb) as a comprehensive repository of fish cell line acute toxicity data. The FACTdb was specifically developed for the OECD TG 249 assay to capture relevant information for interpreting results. This database also offers some flexibility in the way the assay was performed by, for instance, accepting data produced with other fish cell lines. All data integrated require: the use of a fish cell line, cell viability as measured endpoint, exposure time ≤ 96 h, and cells exposed as a confluent monolayer. Data is collected using two templates: the cell viability data template for raw data collection and the experimental metadata template. Together, they allow grouping of data into three OECD TG 249 compliance categories and calculation of effective concentrations and non-toxic concentration values using a consistent analysis pipeline. All public data are available through the freely accessible FACTdb interface, which offers a searchable overview, a detailed view of every entry and the ability to export data as CSV or Excel files. With this database, we aim to provide easy access to available OECD TG 249-based data, enabling, e.g., comparisons across chemicals and test conditions, and supporting read-across and weight-of-evidence approaches. Through this effort, we hope to facilitate the broader uptake and acceptance of the RTgill-W1 cell line assay in environmental safety assessments.