The air quality in the industrial area and surroundings of the city of Paulinia (state of Sao Paulo, Brazil) has been investigated by analysing the concentration of air pollutants (SO2, PM10, NO, NO2, CO and ozone) and identifying the main sources of air pollution. A mobile pollutant monitoring unit was used to collect the data at five different sites from November 2000 to July 2002. Critical pollutants were determined based on air quality standards, and sources were identified by principal component analysis. Photochemical reactions play an important role in Paulinia's air pollution: three out of five monitored sites showed levels exceeding the standard air quality of ozone. SO2 and PM10 appeared as pollutants deserving special attention. All the monitored sites showed vehicles and industrial plants (which release SO2) to be significant sources of pollution. Depending on the location, ozone was related mainly with vehicular or industrial sources.O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.224490506