ABSTRACT
Life cycle assessment (LCA) is the assessment of environmental impacts of a product, process or service across its entire life cycle. This assessment is done based on a particular function of the product or process (for example: the function of drying hands for a hand dryer or providing cleaning service for a cleaning company). A product’s life cycle can include the extraction of raw materials, energy acquisition, its production and manufacturing, use, reuse, recycling and ultimate disposal. All these stages in a product’s life cycle result in the generation of wastes, emissions, and the consumption of resources. These environmental exchanges contribute to impacts such as, climate change, stratospheric ozone depletion, photooxidant formation (smog), eutrophication, acidification, toxicological stress on human health and ecosystems, depletion of resources, and noise pollution among others. LCA allows us to see where a product or service can be improved or manufacturing of new better products. Life cycle impact asssesment is the third phase of LCA in which the flow of materials associated with the product (or process) is translated into consumptions of resources and potential impacts to the environment. The purpose of the impact assessment phase is thus to interpret the life cycle emissions and resource consumption inventory in terms of indicators and to evaluate the impact on the entities that we want to protect.

USEtox is a consensual life cycle impact assessment (LCIA) model developed within the UNEP-SETAC Life Cycle Initiative. The development of this model was an attempt to reduce the variability of different results obtained from using different LCA models. The model allows us to calculate CFs (ie the quantity of environmental impact per quantity of substance emitted) for human toxicity and ecotoxicity which is a product of Effect Factor (EF) and Fate factor (FF). Metal ecotoxicity is considered as poorly modeled by USEtox as the metal speciation is not included within the calculation framework.

During the Clearwater consensus, the need to account for metal speciation has been identified as one of the key priority by a group of experts to improve the ecotoxicological impact assessment of metals in LCA. The bioavailability factor (BF) is included within the definition of CF (CF=BF.EF.FF) which is the ratio of the true solution metal concentration over total metal concentration. To be consistent with the inclusion of bioavailability factor in the CF, it was also recommended to include speciation while calculation the Effect Factor (EF).