Page 227 - Materials Chemistry, Second Edition

4.4 Method of Impact Categories (Environmental Problem Fields) 211

analysis can be integrated into the impact assessment. It is, however, to be made
certain within comparative studies that the symmetry principle is not violated.
To justify the demand for site-specific risk analysis in case of short-ranged or
local impacts (usually not to be accomplished), it is frequently referred to effect
thresholds as follows: it should be of no toxicological and ecological relevance
if pollutants were released in quantities not exceeding PNEC or limits values. 78)
79)
This perception is countered by the less-is-better concept : In compliance with the
precautionary principle, minimisation of all harmful releases is aimed at, even if
laws are not violated and no harmful impacts should occur according to present
knowledge. 80) Particularly persistent and accumulating substances can later have
harmful impacts, even if emitted in small quantities only. 81) This LCA-type of
thinking is also called beyond compliance.
With the greenhouse effect or with the stratospheric ozone depletion the problem
does not occur because it is unimportant where a molecule CO or R11 is released.
2
In summary, regarding the impact assessment, two schools of thought can be
distinguished:

1. The impact assessment refers to potential impacts and adheres to the precau-
tionary principle. 82)
2. The impact assessment, as far as possible, should depend on actual impacts
(polluter pays principle) and its evaluation should base on scientifically derived
or legally specified thresholds and limit values (no endangerment below these
values). 83)

The first school is emphasised in Europe, the second in the USA. A certain freedom
of choice remains and cannot be solved scientifically. The issue of subjectivity in
LCA, 84) in particular in the impact assessment phase is discussed in Chapter 5.
Here, it should be remembered that the problem of subjectivity is relevant even for
the scientifically ‘hard’ phase LCI in the form of the allocation problem.
For a discussion of the impact levels (mid-point vs endpoint) the ‘less-is-better’
debate has the following consequences:
In the context of the first school of thought quantification should be done ‘closest
possible to the inventory interface’ because at that point an exact knowledge of
secondary and tertiary impacts is not necessary (mid-point).
However, in the context of the second school of thought, if an assessment of
causal chains to single impacts deem to be necessary, quantification occurs close
to end points. This will necessarily imply a larger number of subcategories and, as
mentioned above, a more detailed knowledge of space and time dependencies.

78) Hogan, Beal and Hunt (1996).
79) White et al. (1995).
80) Hertwich (1996).
81) Kl¨ opffer (1989, 1994c); this aspect of the precautionary principle has for the first time also been
incorporated into the European chemical regulation act (REACH).
82) Kl¨ opffer and Renner (1995), White et al. (1995), Udo de Haes (1996) and Hertwich (1996).
83) Hogan et al. (1996), Owens (1996) and Barnthouse et al. (1998).
84) Kl¨ opffer (1998a) and Owens (1998).