Hazard and risk-based approaches to comparing toxic emissions

Comparison of the environmental impacts of chemicals, production processes, products, or companies requires methods to interpret emissions data contained in DFE evaluations, life cycle inventories, and toxics release inventories. Impact evaluation methods for toxic substances range from simple toxicity scoring to sophisticated risk-based models. This paper explains two such methods. The environmental impact matrix approach is based on a categorical hazard identification. As a qualitative assessment, it is fairly simple to conduct. It has been used by the Source Reduction Research Partnership to evaluate alternatives to chlorinated solvents. The Human Toxicity Potential (HTP) is based on a multi-pathway environmental exposure model and uses extensive toxicity data. The Dutch government recommended its use in life cycle analysis, along with other equivalency scores, e.g. for global warming, ozone depletion, and smog generation. The steps necessary to calculate an HTP score using the CalTOX model are presented and data needs as well as underlying assumptions are discussed. Differences between the simple scoring mechanism and HTP are illuminated through an example.