USEtox—the UNEP-SETAC toxicity model: recommended characterisation factors for human toxicity and freshwater ecotoxicity in life cycle impact assessment

Abstract

Background, Aim and Scope. In 2005 a comprehensive comparison of LCIA toxicity characterisation models was initiated by the UNEP-SETAC Life Cycle Initiative, directly involving the model developers of CalTOX, IMPACT 2002, USES-LCA, BETR, EDIP, WATSON, and EcoSense. In this paper we describe this model-comparison process and its results-in particular the scientific consensus model developed by the model developers. The main objectives of this effort were (i) to identify specific sources of differences between the models' results and structure, (ii) to detect the indispensable model components, and (iii) to build a scientific consensus model from them, representing recommended practice. Methods. A chemical test set of 45 organics covering a wide range of property combinations was selected for this purpose. All models used this set. In three workshops, the model comparison participants identified key fate, exposure and effect issues via comparison of the final characterisation factors and selected intermediate outputs for fate, human exposure and toxic effects for the test set applied to all models. Results. Through this process, we were able to reduce inter-model variation from an initial range of up to 13 orders of magnitude down to no more than 2 orders of magnitude for any substance. This led to the development of USEtox, a scientific consensus model that contains only the most influential model elements. These were, for example, process formulations accounting for intermittent rain, defining a closed or open system environment, or nesting an urban box in a continental box. Discussion. The precision of the new characterisation factors (CFs) is within a factor of 100-1000 for human health and 10-100 for freshwater ecotoxicity of all other models compared to 12 orders of magnitude variation between the CFs of each model respectively. The achieved reduction of inter-model variability by up to 11 orders of magnitude is a significant improvement.Conclusions. USEtox provides a parsimonious and transparent tool for human health and ecosystem CF estimates. Based on a referenced database, it has now been used to calculate CFs for several thousand substances and forms the basis of the recommendations from UNEP-SETAC's Life Cycle Initiative regarding characterization of toxic impacts in Life Cycle Assessment. Recommendations and Perspectives. We provide both recommended and interim (not recommended and to be used with caution) characterisation factors for human health and freshwater ecotoxicity impacts. After a process of consensus building among stakeholders on a broad scale as well as several improvements regarding a wider and easier applicability of the model, USEtox will become available to practitioners for the calculation of further CFs. Keywords: Consensus model, life cycle impact assessment, LCIA, characterization modelling, comparison, harmonisation, human exposure, toxic impact, human toxicity, freshwater ecotoxicity, comparative impact assessment, characterization factors 1 Background, Aim and Scope In ...

Freshwater ecotoxicity characterisation factor for metal oxide nanoparticles: A case study on titanium dioxide nanoparticle

“…It must be noted that the quantification of the ecotoxicity impacts is one of the most debatable items in LCA (Hischier and Walser, 2012). The variability in model outcomes has been reduced thanks to the USEtox TM model, recently developed by an international collaboration of leading LCIA specialists (Rosenbaum et al, 2008). The USEtox TM provides CFs for organic and inorganic substances for both human toxicity and aquatic freshwater ecotoxicity.…”

“…USEtox TM adopts a PAF (Potentially Affected Fraction of species) based approach to calculate the EF for aquatic ecotoxicity of a substance (Larsen at al., 2007(a,b); Rosenbaum et al, 2008). The PAF is the fraction of species exposed to a concentration above their EC50 (Klepper et al,1998).…”

Evaluating Indoor Exposure Modeling Alternatives for LCA: A Case Study in the Vehicle Repair Industry

“…These models are conceptually similar or compatible to environmental exposure models [19][20][21]. We provide both a qualitative and quantitative evaluation of the capabilities and limitations of each model and also judge its ability to reconstruct and predict actual exposure situations.…”

Accounting for the dissociating properties of organic chemicals in LCIA: An uncertainty analysis applied to micropollutants in the assessment of freshwater ecotoxicity

“…(3) The uncertainties associated with the regression equations adopted in the model to estimate partition coefficients, BCFs and biodegradation rates. (4) The extrapolation of parameter values from one compartment to another (biodegradation rates in biosolids) and from other parameter values (KDOC from KOC). The training and validation sets used to derive the regressions adopted in the model were used to derive residual estimation errors between estimated and experimental data [1,11,12].…”

“…In the USEtox model [4], an ecotoxicological characterization factor (CF) of a chemical in freshwater is the product between a fate factor, that represents the persistence in the environment described by processes such as degradation and inter-compartment transfer, an exposure factor, that represents the bioavailability (i.e., the fraction of chemical dissolved in the freshwater compart-ment), and an effect factor. 21% of chemicals in the USEtox organics database are 50% or more in ionic phase at physiological pH (i.e., acids pKa < 7.4, bases pKa > 7.4).…”