An aggregate air quality index considering interactions among pollutants

Several countries provide an Air Quality Index (AQI) to communicate air pollution, but there is not a unique and nternationally accepted methodology for constructing it. The most of the proposed indices are based on the USA AQI by EPA and are defined by the value of the pollutant with the highest concentration. For each pollutant, a sub-index is computed by linear interpolation according to the grid in a table, but the breakpoints of such a table may differ from one country to another, as well as the descriptors of each category, the air quality standards, the functions chosen as daily synthesis to aggregate hourly values at each site for each pollutant, and so on. Anyway the main drawback is that such indices do not take into account the combined effects of all the considered pollutants, giving little emphasis to effects occurring over long time periods, such as chronic health effects, damages on vegetation, animals, monuments. With the purpose to account for multiple pollutant exposure, some attempts have already been made in literature. In this paper we propose an aggregate AQI which tries to overcome the problems listed above. The proposed index can be easily computed and interpreted, so allowing comparisons among different situations, both in time and space. Moreover, the association of an appropriate measure of dispersion, that can also be considered as a measure of concentration, adds very important information.