OpenChemFacts provides at least on effect factor (EF) for all chemicals displayed on the platform.
Definition
The effect factor (EF) is used to quantify the intrinsic ecotoxicicity of a chemical. It links an environmental concentration of a substance to the fraction of aquatic species expected to be adversely affected.
Effect Factor is expressed in Potentially Affected Fraction (PAF) of species. PAF represents the fraction of species (%) for which a specific concentration (mg/L) would cause effects.
Effect Factor is derived from the concentration (mg/L) corresponding to HC20 (PAF = 20%).
The method used to calculate HC20 values is based on latest scientific guidance : "Ecotoxicity characterization of chemicals: Global recommendations and implementation in USEtox" from 2023 accessible here
EF=CRF=0,2/HC20
Focus on the SSD curve
A concentration-response function (CRF) slope is used to model the relations between concentration (mg/L) and PAF (%).
The slope represents the increase in the potentially affected fraction of species (PAF) per unit increase in chemical concentration, based on a concentration–response relationship.
The Effect Factor is derived from taking the slope on the SSD at the HC20. It represents an incremental change in the potentially affected fraction of species due to an incremental exposure to the bioavailable concentration of a chemical at the HC20 level.
How are calculated effect factors ?
Effect Factors are calculated through a complex data pipeline.
