Midpoints versus endpoints: The sacrifices and benefits

Abstract

Abstract. On May 25-26, 2000 in Brighton (England), the third in a series of international workshops was held under the umbrella of UNEP addressing issues in Life Cycle Impact Assessment (LCIA). The workshop provided a forum for experts to discuss midpoint vs. endpoint modeling. Midpoints are considered to be links in the cause-effect chain (environmental mechanism) of an impact category, prior to the endpoints, at which characterization factors or indicators can be derived to reflect the relative importance of emissions or extractions. Common examples of midpoint characterization factors include ozone depletion potentials, global warming potentials, and photochemical ozone (smog) creation potentials. Recently, however, some methodologies have adopted characterization factors at an endpoint level in the cause-effect chain for all categories of impact (e.g., human health impadts in terms of disability adjusted life years for carcinogenicity, climate change, ozone depletion, photochemical ozone creation; or impacts in terms of changes in biodiversity, etc.). The topics addressed at this workshop included the implications of midpoint versus endpoint indicators with respect to uncertainty (parameter, model and scenario), transparency and the ability to subsequently resolve trade-offs across impact categories using weighting techniques. The workshop closed with a consensus that both midpoint and endpoint methodologies provide useful information to the decision maker, prompting the call for tools that include both in a consistent framework.

Possibilities and limitations of LCA for the evaluation of soil remediation and cleanup

“…These indicators are characterized by a relatively low uncertainty and a relatively easy interpretation. On the other hand, end point indicators such as biodiversity have to deal with a lot of uncertainty, which should also be accounted for in LCA [29].…”

Assessing Environmental Impacts in a Life-Cycle Perspective

“…A valuation is needed only for areas of protection, whereas the midpoint approaches must evaluate a higher number of midpoint-based impact scores. This evaluation must somehow interpret the potential to cause damage to areas of protection (24). For example, the midpoint approach would entail a semiquantitative analysis of the unmodeled parts of the impact pathway, in which the severity and reversibility of the impacts on endpoints, their geographical extent and expected duration, and the models' uncertainties are considered (11).…”

“…And, as larger parts of the impact pathway are included in the characterization modeling, the midpoint approach will become more like the damage approach. Until they converge, the two approaches will complement each other (24). Work is under way to make the two approaches compatible (16,25).…”

Environmental damage estimations in industrial process chains

“…It models and evaluates selected environmental issues, called impact categories, and through the use of category indicators portrays the potential environmental impact of the environmental loads in an aggregated manner. There have been a number of advances made in the evaluation of environmental impacts in Life Cycle Assessment in recent times (Bare et al, 2000):…”

“…global warming potentials defined in terms of radioactive forcing and atmospheric half-life differences). That is, midpoints are located a step before endpoints and allow to calculate in a relative way the environmental impact of any emission defined in the Life Cycle Inventory (Bare et al, 2000). Historically, the midpoint approaches have set the scene in LCIA, taken as prominent examples the thematic approach (Heijungs et al, 1992), the Sandestin workshop on LCIA (Fava et al, 1993), the Nordic LCA guide (Lindfors et al, 1995), the Eco-indicator 95 method (Goedkoop, 1995) and the EDIP model (Wenzel et al, 1997).…”