Page 288 - Materials Chemistry, Second Edition

272 4 Life Cycle Impact Assessment

Germany. If the EU is the geographical boundary, averages from EU states could be
applied, for international studies average from the OECD countries. (OELs of little
industrialised states may be inspired by those of the industrialised countries). A
worldwide labour protection organisation (ILO) based in Geneva lists those values
from all over the world. Thus a data base of international scale were given which at
least for substances with effect threshold values would allow a relative weighting.
A summary of international OELs (D, EU; USA; GUS) has been published by
Sorbe. 287) In this work which also lists other toxicological limit values, an overall of
18 000 substances are listed.
All lists should be critically reviewed as to whether limit or indicative values
for the considered substances have been deduced according to uniform methods
(scientific data base, considered impacts, duration of exposure, target groups,
security factors, acceptable risk and other boundary conditions). If the explanatory
framework of listed substances varies considerably, the lists do not meet the criteria
of a reliable ranking of toxicity of substances relative to each other. As such, the limit
value for a substance A within an explanatory framework ‘working site protection’
deduced for an exposure of healthy employees for five days a week 8 hours a day
cannot be compared with that of a substance B with respect to the in-house air
in apartments deduced for a continuing exposure including sensitive population
groups, in a single list for a relative weighting of toxicity of A and B. An adaption of
multiple lists of those values into one without a critical reflection of the explanatory
framework is therefore prohibited.
Table 4.15 exemplifies inconsistencies concerning the mix of limit and indicative
values from various explanatory frameworks for three well-known substances:
MAK-values are juxtaposed indicative values for substances of the indoor air
pollution. With regard to their use for weighting in the impact assessment the
absolute values are not the subject in this discussion. This example shows that
values can vary according to varying explanatory frameworks and the relative order
of substances can change.
A method comparison in the US 288) introduces a characterisation equivalent to
the ‘MAK method’ within the group ‘comparison of toxicity’ but proposes the use
of Acceptable Daily Intake (ADI) values for characterisation:
( Q )
TBS = ∑ i m (4.25)
Q i
i ref
TBS, Toxicity-based scoring
Q 1/ADI (kg body weight × d/mg); reciprocal ADI of the substance i
i
i

287) Sorbe (1998).
288) Hertwich, Pease and McKone (1998).