Page 291 - Materials Chemistry, Second Edition

4.5 Impact Categories, Impact Indicators and Characterisation Factors 275

without a collapse of the ecosystem. Nature has coped with the extinction of
many species. This cannot be, however, a license for the present-day practice of
extinction of species by humans, because of totally different time scales! Protection
of species is therefore a very important short time goal; in the long term, however,
the ecosystem aspects prevail. Referring to Lovelock again one could say ‘Gaia’s
ability for learning has to be sustained’, create new species and thus biodiversity is
sustained as a long-term result. This problem field is closely related to time scales
(‘time ecology’). 298)
Without restriction to any method proposed in literature the working group
‘Impact Assessment of Human an Ecotoxicity in Life Cycle Assessment’ of SETAC
Europe 299) has proposed the following general formula for treatment of human
toxicity
m
S = E F M n (4.26)
i i i i
E effect factor (EF)
F fate (distribution and degradation)
M mass (load per fU).
The score (S)ofasubstance i for the environmental compartment m is at the
left of the Equation 4.26. The original emission was released into compartment
n(n = m is the only case considered for a simple weighting). It is attempted to
integrate exposure and effect into one equation which is the basic principle for
a risk assessment of chemicals. The first expression on the right side is the EF
weighting the considered adverse effect in compartment m. This factor can be very
similar to usual weighting factors, for example:

E = 1 (4.27)
m
i m
NEC
i
NEC = no effect concentration or NOEC = no observed effect concentration of sub-
stance i in compartment m (e.g. a volatile chemical in compartment air).
With such a definition of the weighting factor for the effect Equation 4.26 – except
for notation – differs from Equation 4.27 only by the factor F. Still not included is
the summation of the results for all toxic substances quantified in the inventory.
The second expression on the right in Equation 4.26 is the fate and exposure
factor 300) of substance i, which has been emitted into compartment n and transferred
into compartment m (e.g. by evaporation, deposition, etc.) considering degradation
processes and accumulation. It can be observed that this factor can only be deter-
mined by modelling or by estimations with knowledge of physical and chemical
properties of the molecule. Such calculations are part of the risk assessments
of chemicals, but however, of little reliability because of multiple simplifying
assumptions and low quality of input data. 301)

298) Held and Geißler (1993, 1995) and Held and Kl¨ opffer (2000).
299) Jolliet et al. (1996): Impact Assessment of Human and Eco-toxicity in Life Cycle Assessment, in:
Udo de Haes (1996, S. 49–61).
300) Jolliet et al. (1996).
301) Kl¨ opffer (1996a, 2002, 2004) and Kl¨ opffer and Schmidt (2003).