Sources of indoor air pollution at a New Zealand urban primary school; a case study

Children are particularly vulnerable to the health effects of air pollution and as they spend a large proportion of time at school, this is an important environment for children's exposure to air pollution. Understanding the factors that influence indoor air quality in schools is critical for the assessment and control of indoor air pollution. This study analysed the concentration and sources of air pollution at an urban primary school (5–11 years) in Wellington, the capital of New Zealand. Over a three-week period during spring, indoor measures of particulate matter (PM2.5, PM10), temperature, humidity, carbon dioxide (CO2) and nitrogen dioxide (NO2) were taken and hourly air particulate matter samples (PM2.5, PM10-2.5) were collected inside and outside for elemental speciation analysis. Indoor PM10 concentrations during the school day were significantly (p < 0.001) higher than outdoor concentrations 30.1 (range 10.0–75.0, SD 1.9) μg m−3 c.f. 8.9 (range <1.0–35.0, SD 6.8) μg m−3. Elemental analysis and receptor modelling of PM samples showed that indoor PM10 was primarily composed of crustal matter (soil) elements, possibly brought in on children's footwear. The primary driver of indoor PM2.5 was from the infiltration of outdoor pollutants inside, with by-products of motor vehicle emissions the main contributor to indoor PM2.5. There is a need for mitigation strategies to reduce exposure to indoor air pollution at school, such as improved cleaning methods, reducing the use of carpet in schools and improved ventilation. The findings from this study will be applicable to many other schools and public buildings with high foot traffic.