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overview of the AoPs with underlying societal values, as presented by Udo de Haes
and Lindeijer (2001). Because the AoPs are the basis for the determination of relevant
endpoints, their definition implies value choices. Thus, there is no one scientifically
correct way to define a set of AoPs (Udo de Haes et al., 2002).
Udo de Haes and Lindeijer (2001) propose to differentiate among the sub-AoPs’
life support functions, natural resources and biodiversity, and natural landscapes
within the AoP natural environment. Life support functions concern the major
regulating functions of the natural environment, which enable life on Earth (human
and nonhuman). These particularly include the regulation of the Earth’s climate,
hydrological cycles, soil fertility and the bio–geo–chemical cycles. Like manmade
environments (materials, buildings, crops, livestock) and natural resources, the life
support functions are of functional value for society. From a value perspective, these
are fundamentally of another nature than those of AoPs with intrinsic value to society,
particularly those connected with human health, biodiversity and natural landscapes,
works of art, monuments and manmade landscapes. An overview of the classification
of AoPs according to societal values is presented in Figure 3.4.

3.5 MIDPOINT AND ENDPOINT INDICATORS

The terms midpoint and endpoint refer to the level within the environmental mech-
anism at which the respective effects are characterized. In general it is assumed that
an indicator defined closer to the environmental intervention will result in more
certain modeling and that an indictor further away from the environmental interven-
tion will provide environmentally more relevant information (i.e., more directly
linked to society’s concerns and the areas of protection). Although midpoints and
endpoints can be overlapped in same cases, midpoint indicators are used to measure
a substance’s potency of effect, which in most cases is characterized by using a
threshold, and does not take into account the severity of the expected impact. Figure
3.5 shows a schematic illustration of the definition of midpoint and endpoint levels
(Olsen et al., 2001).
According to Udo de Haes and Lindeijer (2001), historically, the midpoint
approaches have set the scene in LCIA; some prominent examples include 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). They also
have mostly structured the way of thinking and examples chosen in ISO 14042
(2002).
Since the middle of the 1990s the endpoint approach has been set on the agenda
(Udo de Haes and Lindeijer, 2001). Particularly in LCA studies that require the analysis
of tradeoffs between and/or aggregation across impact categories, endpoint-based
approaches are gaining popularity. Such methodologies include assessing human health
and ecosystem impacts at the endpoint that may occur as a result of climate change
or ozone depletion, as well as other categories traditionally addressed using midpoint
category indicators. The endpoint approach already has a longer history, particularly
in the EPS (environmental priority strategy) approach from Steen and Ryding (Steen
and Ryding, 1992; Steen, 1999); however, it has received a strong impetus from the

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