Back to Top

The USEtox Model

USEtox is a model based on scientific consensus providing midpoint and endpoint characterization factors for human toxicological and freshwater ecotoxicological impacts of chemical emissions in life cycle assessment, developed under the auspieces of the United Nations Environment Program (UNEP) and the Society for Environmental Toxicology and Chemistry, (SETAC) Life Cycle Initiative. USEtox represents best application practice as an interface between ever advancing science and a need for stability, parsimony, transparency, and reliability. The impact pathways covered by USEtox are shown in Figure 1.

USEtox framework
 Figure 1. USEtox comparative toxicity assessment framework (click to enlarge).


The USEtox model operates on different scales; indoor environment, urban scale, continental scale and global scale. The continental and global scales each consist of five compartments, namely rural air, agricultural soil, natural soil, freshwater, and (coastal) marine water. The compartment structure of USEtox is shown in Figure 2.

USEtox compartments
Figure 2. USEtox environmental compartment structure.


The main output of USEtox are interim and recommended characterization factors, which should always be used together. Excluding interim characterization factors is in principle only meaninful for sensitivity analysis in an life cycle assessment study. The model and database include environmental fate, exposure, and effect parameters for human toxicity and freshwater ecotoxicity. Characterization factors are calculated by following three steps:

  1. Environmental fate, where the distribution and degradation of each substance is modelled,
  2. Exposure, where the exposure of humans, animals and plants is modelled, and
  3. Effects, where the inherent damage of the substance is modelled.

USEtox will be constantly improved (by including new chemicals, etc.) and is recommended for comparative chemical toxicity assessment by the European Union, the United States - Environmental Protection Agency, and other organizations. USEtox is increasingly used in a wide range of national and international projects as well as in industrial life cycle assessment studies. For details see Publications.