Indoor air quality in schools of a highly polluted South Mediterranean area

This study aimed at surveying lower secondary schools in southern Sicily, Italy, in a highly polluted area. A small city close to an industrial area and three villages in the surrounding rural areas were investigated. Indoor temperature, relative humidity (RH), gaseous pollutants (CO2 and NO2), biological pollutants (LPS and Der p 1) in indoor dust, and the indoor/outdoor mass concentration and elemental composition of PM2.5 were ascertained. In most cases, temperature and RH were within, or close to, the comfort range, while CO2 at times significantly exceeded the threshold of 1,000 ppm, indicating inadequate air exchange rate. In all the classrooms, median NO2 levels were above the threshold value of 40 µg/m3. Dermatophagoides p. allergen concentration was always below the sensitizing threshold, while high levels of endotoxin were detected in the classrooms, suggesting that schools may produce significant risks for endotoxin exposure. Indoor PM2.5 elemental concentration was higher than outdoors. For elements deriving from industrial emission the indoor concentration depended on penetration from the outside. Differences in concentration between industrial and rural sites were found, showing that industrial sources may have a non-negligible influence on the indoor air quality of schools.