Impact Analysis

The impact analysis component of the LCA is a technical, quantitative, and qualitative process to characterize and assess the effects of the resource requirements and environmental loading (atmospheric and waterborne emissions and solid waste) identified in the inventory stage. Methods for impact analysis under development follow those presented at a SETAC workshop in 1992. The EPA's Office of Air Quality Planning has two documents which address life cycle impact analysis. (See also Chapter 2.)

The key concept in the impact analysis component is that of stressors. The stressor concept links the inventory and impact analysis by associating resource consumption and the releases documented in the inventory with potential impact. Thus, a stressor is a set of conditions that may lead to an impact. For example, a typical inventory quantifies the amount of SO2 releases per product unit, which may then produce acid rain and then in turn affect the acidification of a lake. The resultant acidification might change the species composition and eventually create a loss of biodiversity.

Impact analysis is one of the most challenging aspects of LCA. Current methods for evaluating environmental impact are incomplete. Even when models exist, they can be based on many assumptions or require considerable data. The following sections describe several aspects of impact assessment and their limitations when applied to each of the major categories of environmental impact.

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