Predicted environmental impact and expected occurrence ofActual environmental impact part 1: The linear nature of environmental impact from emissions in life-cycle assessment

The necessity of the impact assessment phase in life-cycle assessment (LCA) is presently debated. The crux of the debate lies in the poor accordance in some I.CA studies between the predicted environmental impact and the expected occurrence of actual environmental impact. That is in particular the case for impacts of a continental, regional and local character. We consider an impact assessment as being an indispensable phase of LCA, and see options for solving the identified problem. This article takes a closer look into the nature of the assessed impact in LCA in order to provide the basis for enhancement of life-cycle impact assessment. LCA is one of the analytical tools to support environmental policy focused on the control of present environmental problems. Nowadays, environmental problems are caused by concentration levels that result from the emissions of many sources together, rather than from single sources alone. The contribution from a single source is usually small or even marginal in comparison with the total contribution from all sources together. The multiple source character of the related impact categories provides the justification for the linear nature of the assessed impact in LCA. An article in the next issue of this journal will build further on this article, and will discuss the inclusion of temporal and spatial aspects (by a site-dependent approach) in order to enhance the accordance between the predicted environmental impact and the expected occurrence of actual environmental impact.