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

Abstract

An exposure study of children (aged 10–12 years) living in Santiago, Chile, was conducted. Personal, indoor and outdoor fine and inhalable particulate matter (<2.5 μm in diameter, PM 2.5 and <10 μm in diameter, PM 10, respectively), and nitrogen dioxide (NO 2) were measured during pilot ( N=8) and main ( N=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 PM 2.5 concentrations (69.5, 68.5 and 68.1 μg m −3, respectively) were found. However, for coarse particles (calculated as the difference between measured PM 10 and PM 2.5, PM 2.5–10) indoor and outdoor levels (35.4 and 47.4 μg m −3) were lower than their corresponding personal exposures (76.3 μg m −3). Indoor and outdoor NO 2 concentrations were comparable (35.8 and 36.9 ppb) and higher than personal exposures (25.9 ppb). Very low ambient indoor and personal O 3 levels were found, which were mostly below the method's limit of detection (LOD). Outdoor particles contributed significantly to indoor concentrations, with effective penetration efficiencies of 0.61 and 0.30 for PM 2.5 and PM 2.5–10, respectively. Personal exposures were strongly associated with indoor and outdoor concentrations for PM 2.5, but weakly associated for PM 2.5–10. For NO 2, 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 PM 2.5 were close to unity, and for NO 2 they ranged between 0.64 and 0.95. These ratios were probably due to high ambient PM 2.5 and NO 2 levels in Santiago, which diminished the relative contribution of indoor sources and subjects’ activities to indoor and personal PM 2.5 and NO 2 levels.