Page 298 - Materials Chemistry, Second Edition

282 4 Life Cycle Impact Assessment

comprises a thorough study of damaging impacts on diverse species caused by
damaging substances and set up mechanisms. A transmission of these single find-
ings on all possible species and particularly on ecosystems (see above) is at present
not possible and, in the case of the ecosystems, is probably not possible at all.
The actual protection goal in the impact category ecotoxicity can be described
by the prospering, quality and sustainability of the natural ecosystems, but cannot
be satisfactorily defined. It has been tried, mostly in the US, to introduce the
descriptive metaphor ecosystem health as the actual protection goal. This was
strongly contradicted by Suter 330) in an analysis of the term and its consequences
(see Section 4.5.3.2.3). The expression health suggests an understanding of the
functioning of ecosystems, which is not true 331) , and that sick ecosystems could
be healed. A more suitable expression for the higher goal of protection suggested
by Suter is quality or sustainability of ecosystems, and examples of the necessary
investigations and data for characterisation are provided.
4.5.3.3.3 Simple Quantification of Ecotoxicity without Relation to Exposure Similar
to the impact category human toxicity there is a ‘zeroth approximation’. 332) for
ecotoxicity; a primary loaded compartment (m = n) is considered in Equation 4.26
and the fate factor is not regarded (F = 1). Under this boundary conditions a large
NEC list provided by, for example, US EPA, 333) can be used for weighting in the
regarded compartment (ecotoxicity potential, ETP, according to Equation 4.29). As
discussed for the use of the OELs like MAK- or ADI values for human toxicity, the
NEC values are exclusively applied for a relative weighting of emissions into water
or soil as determined in the inventory (LCI). By application of this simple method
a division into two indicators, one for water and one for soil, cannot be avoided, if
ecotoxicity in the soil compartment is not neglected for lack of data.
( m )
ETP = ∑ i (l water or kg soil per fU) (4.29)
NEC
i i
with m = mass of substance i released into water and/or soil with a documented
i
NEC value, per fU. ETP is usually separated into an aquatic (ETPA) and a terrestrial
i
ecotoxicity potential (ETPT). The unit of the ETP (l water; kg ground) results from
the units of NEC values, common units are mg l −1 for water and mg kg −1 dry weight
(‘ppm’) for soil. The load per fU from the inventory should be used accordingly in
milligrams.
Another option would be an ETP or ETPA or ETPB in Equation 4.29 by quotient
formation on any reference substance (e.g. 1,4-dichlorobenzene), with its ETP
arbitrarily set to one. The indicator result then reads ‘kg of DCB equivalents’ per
fU for ecotoxicity in water or in soil. The only argument against such units is the
same as for HTPs: it assumes a similar mechanism for all aggregated emissions
whereas in reality there may be a totally different impact context.

330) Suter (1993).
331) Schmid and Schmid-Araya (2001).
332) The expression ‘zeroth approximation’ originates from quantum physics and designates a
theoretical problem solution, which excludes interactions between subsystems.
333) Heijungs et al. (1992) and Kl¨ opffer and Renner (1995).