Measurements of children’s exposures to particles and nitrogen dioxide in Santiago, Chile

An exposure study of children Žaged 10 12 years. living in Santiago, Chile, was conducted. Personal, indoor and outdoor fine and inhalable particulate matter Ž 2.5 m in diameter, PM2.5 and 10 m in diameter, PM10, respectively., and nitrogen dioxide ŽNO2. were measured during pilot ŽN 8. and main ŽN 20. studies, which were conducted during the winters of 1998 and 1999, respectively. For the main study, personal, indoor and outdoor 24-h samples were collected for five consecutive days. Similar mean personal, indoor and outdoor PM2.5 concentrations Ž69.5, 68.5 and 68.1 g m3, respectively. were found. However, for coarse particles Žcalculated as the difference between measured PM10 and PM2.5, PM2.5 10 ., indoor and outdoor levels Ž35.4 and 47.4 g m3. were lower than their corresponding personal exposures Ž76.3 g m3.. Indoor and outdoor NO2 concentrations were comparable Ž35.8 and 36.9 ppb. and higher than personal exposures Ž25.9 ppb.. Very low ambient indoor and personal O3 levels were found, which were mostly below the method’s limit of detection ŽLOD.. Outdoor particles contributed significantly to indoor concentrations, with effective penetration efficiencies of 0.61 and 0.30 for PM2.5 and PM2.5 10 , respectively. Personal exposures were strongly associated with indoor and outdoor concentrations for PM2.5, but weakly associated for PM2.5 10. For NO2 , weak associations were obtained for indoor outdoor and personal outdoor relationships. This is probably a result of the presence of gas cooking stoves in all the homes. Median I O, P I and P O ratios for PM2.5 were close to unity, and for NO2 they ranged between 0.64 and 0.95. These ratios were probably due to high ambient PM2.5 and NO2 levels in Santiago, which diminished the relative contribution of indoor sources and subjects’ activities to indoor and personal PM2.5 and NO2 levels.