An aggregate AQI: comparing different standardizations and introducing avariability index

Many studies demonstrate a strong relationship between air pollution and respiratory and cardiovasculardiseases. For this reason, assessing air pollution, and conveying information about its possible adverse healtheffects, may encourage population and policy makers to reduce those activities increasing pollution levels. Inthis paper a relative index of variability, to be associated with the aggregate Air Quality Index (AQI) amongpollutants proposed by Ruggieri and Plaia (2011), is developed in order to better investigate air pollutionconditions for the whole area of a city/region. The most widely-used and up to date pollution indices,based mainly on AQI computed by the US Environmental Protection Agency (EPA) and often defined bythe value of the pollutant with the highest (opportunely standardized) concentration on a given day, aimat warning the people for short term health impact. An aggregate AQI, taking into account the combined effectsof all the considered pollutants, gives emphasis to possible chronic health effects and long term damageson environment caused by air pollution. The proposed index of variability adds precious information to theaggregate AQI, as it allows one to know whether the value assumed by the AQI is influenced by one ormore pollutants. The two indices are jointly used on simulated data, considering different possible scenarios.Applications to real air pollution data are also reported. Before applying the two indices, the effects of differentstandardizations on data are evaluated from a theoretical point of view.