Frequently Asked Questions - How to use USEtox characterization factors

In USEtox, persistent and bioaccumulative chemicals are considered and included in the chemical database. These compounds typically have high characterization factors due to the significant potential for exposure through multiple pathways. If such substances are moderately soluble, this will yield lower eco-exposure factors. However, due to the generally high fate factors (i.e. long persistence in the environment) and higher bioaccumulation potential, overall characterization factors for such substances are typically large as compared to other chemicals.

For considering consumer exposure, a near-field/far-field modeling framework was developed and is available (Fantke et al. 2016, Fantke et al. 2021) that was recommended in the global UNEP-SETAC GLAM effort to be implemented in USEtox as from version 3. This framework has already been applied in various case studies, is fully mass balance based and aligned with USEtox, which allows to combine impacts from product constituents with impacts from emissions along product life cycles.

For human toxicity, cancer and non-cancer health impacts are considered separately as indicators of disability in USEtox versions 1 and 2. Non-cancer effects are furthermore differentiated into reproductive/developmental toxicity and general non-cancer toxiity as from USEtox version 3 (see Fantke et al. 2021, based on underlying points of departure developed in Aurisano et al. 2023 for oral expsoure and Aurisano et al. 2024 for inhalation exposure). Since all underlying available test data per chemical should be used to derive USEtox effect factors from the lowest converted human lifetime dose per exposure route, all underlying effects are considered in USEtox.

USEtox versions 1 and 2 apply a generic acute-to-chronic ratio of 2 (see Jolliet et al. 2003) and is confirmed by current, much broader studies (Posthuma et al. 2019, Aurisano et al. 2019). This fixed ratio does not account for variability across chemicals and species.