Page 203 - Materials Chemistry, Second Edition

4.3 Structure of Impact Assessment according to ISO 14040 and 14044 187

substances that are either only produced in very small quantities or considered
as harmless because they have so far never been correlated with poisoning or
environmental problems.
4. Most limit values only consider human health and thus do not cover ecological
toxicity. Limit values at the ecological system level do not exist at all. An extreme
example is carbon dioxide, which for humans is only poisonous in very high
concentrations. The gas to date is regarded as the most important greenhouse
gas (GHG, see Section 4.5.2.2). It was, however, not included in BUWAL 1991
16)
for a computation of the c.V. of air and thus not evaluated , for lack of limit
values.

4.3
Structure of Impact Assessment according to ISO 14040 and 14044
4.3.1
Mandatory and Optional Elements

The LCIA phase according to ISO 14040 and 14044 17) has got a structure, which is
composed of mandatory and optional elements.
Mandatory elements:
• Selection of impact categories, category indicators and characterisation models;
• Assignment of LCI results (classification);
• Calculation of category indicator results (characterisation).
The impact category indicator results are the results of the mandatory elements of
the impact assessment. They are generated according to scientific rules.
Optional elements:
• Calculation of the magnitude of impact category indicator results relative to
reference information (normalisation);
• Grouping;
• Weighting.
An application of optional elements to the impact category indicator results leads
to weighted data. The priority criteria of the optional elements can be scientifically
justified only in parts (see Section 4.3.3).

4.3.2
Mandatory Elements

4.3.2.1 Selection of Impact Categories – Indicators and Characterisation Factors
The terms impact category, category indicator and characterisation factor are defined
as follows in ISO 14044:

16) Neither in US-American legislation CO has been considered as pollutant until recently.
2
17) ISO (2006a, Section 5.4) and ISO (2006b, Section 4.4).