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• Study objective
• Inventory data and availability of accompanying parameters
• Depth of knowledge and comprehension in each impact category
• Quality and availability of modeling data
• Uncertainty and/or sensitivity analysis
• Level of financial resources

3.9 INTERPRETATION
To conclude the LCIA step, the practitioner must carry out analysis and interpretation
of its results in order to evaluate the environmental performance of the product or
activity under investigation. The actual assessment of the environmental profile of the
product takes place during the evaluation. The nature of the assessment is determined
by the goal step of the study. Usually, this will be a comparative assessment. Other
examples include providing information about the environmental performance of the
product regarding some function, product regulation by government agencies, bench-
marking and comparing a product with one or more possible alternatives of its redesign.
The interpretation is an independent step when the goal of the LCA is to find
options to improve a product. During the improvement analysis, environmental LCA-
based product information is used to make recommendations about the optimization
of its manufacturing (including actions of processess or product design) or changes
concerning its use by the consumer, e.g., washing at low temperature.
In any case, some priorities need to be established in order to guide the work
of the practitioner. In this frame, questions like “What is more important at this
moment?” or “What comes first: dealing with the greenhouse effect or with photo-
oxidation formation?” or “In terms of LCI, should the first action be to reduce the
CO emissions or the COD (chemical oxygen demand) generation?” define the type
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of evaluation to be carried out during the interpretation step.
The LCIA generates an environmental profile of the product consisting of a certain
number of impact potentials that help to compare product alternatives. It depends on
the specific case if it will then be possible to draw a conclusion without further
weighting. In principle, this is only possible when all of the impact potentials of a
product alternative are better than those of the other product (Heijungs et al., 1992).
However, in many cases, one product alternative will present a better environ-
mental performance for some impact potentials but worse on others. In cases like
this, the impact potentials will have to be rated in order to make an assessment.
Usually, two methods can be used for this: qualitative multicriteria analysis and
quantitative multicriteria analysis. As presented by Heijungs et al (1992), both
methods include methodological as well as procedural aspects. The procedural
aspects are largely concerned with issues such as who will undertake the evaluation
and what information is provided to those concerned.
In the qualitative method a panel rates the better and poorer impact potentials
(see eco-indicator 99 example in Section 3.7.5). The advantage of this method is that
all involved parties can express their points of view, furnishing a multidisciplinary
perspective to data interpretation. A clear disadvantage is the loss of uniformity
inherent to the method: when two different persons assess a set of two environmental
profiles, their results can be highly different.

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