Local pollution is expressed in terms of several components: sulphides, nitric oxides, and
particulate matter (neglecting pollution by CO2, which is global in nature, and which is discussed below).
The methods of evaluation used here are primarily of the indirect type, involving first of all a technical
estimate of the damage done, and then an evaluation of the "cost of repairs or protection". "Substitution
market" methods are less common here than for noise. As for "contingent valuation" methods, these are
occasionally used, but they tend to produce very different results.