National directives on air quality oblige nations to monitor and report on their air quality, allowing the public to be informed
on the ambient pollution levels. The last is the reason for the always increasing interest, demonstrated by the number of
publications on this topic in recent years, in air quality/pollution indices: since the concentration of individual pollutants
can be confusing, concentration measurements are conveniently transformed in terms of an air quality index. In this way, complex
situations are summarized in a single figure, letting comparisons in time and space be possible. In this paper we will give
an overview about the Air Quality/Pollution Indices proposed in literature and/or adopted by countries, trying also to categorize
them into homogeneous groups. For the classification different approaches can be followed. Since in real life exposure to
mixtures of chemicals occurs, with additive, synergistic or antagonistic effects, here we will distinguish between indices
that consider the conjoint effect of pollutants and indices only based on the actual most dangerous pollutant. This brief
review on air pollution indices shows, on one side, the wide interest in the problem, on the other, the lack of a common strategy
which allows to compare the state of the air for cities that follow different directives. The main differences between the
indices will be also described.
KeywordsAir quality indices–Pollution indices