A decision-analytic framework provides a consistent, systematic structure for impact assessment.  Similar stressors, such as toxic chemicals, are evaluated by constructed attributes, such as HTP.  These attributes relate to our fundamental objectives through causal relationships. Decision analysis provides criteria for method development.
The comparative evaluation of environmental stressors serves to support environmental policy as well as private pollution prevention efforts.  This thesis addresses the evaluation of toxic emissions in product life-cycle assessment, and it provides a framework and theoretical foundation for such comparative evaluations.  The Human Toxicity Potential developed here, as well as the structure of the broader assessment, is applicable to other decision support tools in Industrial Ecology and environmental policy.

The Human Toxicity Potential (HTP) is a weighting factor that expresses the release of a toxic chemical in terms of an equivalent release of a reference chemical.  It is based on the toxicity of a chemical as well as its potential dose.  Applicable measures of toxicity are U.S. EPA’s cancer potency and reference dose.  The potential dose is evaluated by a multimedia, multiple pathway fate and exposure model, CalTOX.  CalTOX determines pollutant concentrations in uniformly mixed environmental compartments from intercompartmental mass transfer equations. It models exposure pathways using partitioning and biotransfer relationships.  The potential dose is based on exposure media concentrations, diet, and activity pattern.
A systematic uncertainty analysis addresses parameter, model, and decision-rule uncertainty as well as variability in the potential dose.  It serves to increase the confidence in HTP and to provide the information necessary to evaluate the reliability of decisions based on this indicator.