“…These methods generally make use of statistical techniques such as regression or other data-fitting methods using numerical techniques to establish the respective relationships between the various physicochemical parameters and variable of interest based on routinely-measured historical data. The main objectives of these methods include investigating and assessing trends in air quality, making environmental forecasts and increasing scientific understanding of the mechanisms that govern air quality (Thompson et al, 2001). Among the techniques being examined to relate air quality in a given area to measured physical and chemical parameters, the three that have been used most often are i) multivariate regression (Hubbard & Cobourne, 1998, Comrie & Diem, 1999, Davis & Speakman, 1999Draxler, 2000, Gardner & Dorling, 2000, ii) artificial neural networks (ANN) (Perez & Reyes, 2006;Brunelli et al, 2006;Thomas & Jacko, 2007;Grivas & Chaloulakou, 2005;Gardner & Dorling, 1999), and iii) time series and spectral analysis (Raga & Moyne, 1996, Chen et al, 1998Milanchus et al, 1998, Salcedo et al, 1999, Sebald et al, 2000.…”