Although the science of life cycle assessment has
increased in sophistication in recent years,the process
can only account for the impact categories actually
inventoried. It is probably impossible to inventory all
impacts. The combination of impact categories requires
weighting; weighting of categories requires value judgements;
and therefore weighting is the most critical and
controversial step in LCIA. Nevertheless,in a world
where every human activity has environmental impacts,
it is important to strive for the best informed conclusions
possible.