Measurements of children's exposures to particles and nitrogen dioxide in Santiago, Chile
Introduction
In Santiago, Chile, particulate matter and ozone levels frequently exceed the national ambient air quality standards (CONAMA, 1997, CONAMA, 2000) and are higher than observed in the United States and Western Europe (Ostro et al., 1996). These elevated concentrations result from the numerous air pollutant sources and the local topographic and meteorological conditions. Santiago is located in a closed basin, where temperature inversion layers are frequently formed, especially during the winter season (CONAMA, 1997). The high air pollutant levels could have a significant impact on public health. Epidemiological studies conducted in Santiago and elsewhere have found ambient particle and gaseous co-pollutant concentrations to be associated with morbidity indicators and increased mortality (Pope et al., 1991, Dockery et al., 1993, Dockery and Pope, 1994, Ostro et al., 1996, Schwartz et al., 1996, Borja-Aburto et al., 1997, Ilabaca et al., 1999). Sensitive groups have been identified to be children, the elderly and individuals with respiratory and cardiovascular diseases. In order to enhance our understanding of the health effects of air pollution, it is necessary to characterize indoor and personal exposures and examine their relationship with ambient levels (Clayton et al., 1993, Tamura et al., 1996, Janssen et al., 1998, Rojas-Bracho et al., 2000, Bahadori et al., in press).
To characterize particle and gaseous exposures of children (aged 10–12 years) living in Santiago, Chile, we conducted a pilot (N=8) and a main study (N=20), during the winters of 1998 and 1999, respectively. In both studies, participants were followed for five consecutive weekdays. During the pilot study, we measured 12-h personal, indoor and outdoor concentrations of particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone (O3). In addition, we collected information on household characteristics and time–activity patterns. Overall, this pilot study demonstrated the feasibility of conducting an exposure assessment study for children in Santiago.
Based on the pilot study results, we designed the main study to characterize personal, indoor and outdoor exposures to PM2.5, PM10, PM2.5–10, NO2 and O3. We excluded SO2 measurements because its concentrations were extremely low, and we shifted from 12- to 24-h sampling periods to improve the limits of detection (LODs) of NO2 and O3 measurement methods. In spite of this, during the extended study, most personal, indoor and outdoor O3 levels were below the method's LOD. [Low wintertime ambient ozone concentrations are typical of Santiago (CONAMA, 2000).] For this reason, we did not include O3 in the statistical analyses and all references were excluded from the manuscript. This paper presents the design, methods, quality control/quality assurance procedures and results from the statistical analyses of the main study.
Section snippets
Methods
A total of 20 children living in non-smoking households from the Santiago metropolitan area volunteered to participate in the main study. These children were recruited from four schools: Hermanos Matte, Rafael Sanhueza, San Ignacio and Alianza Francesa. All of the schools and homes of the participants were located in the central and northeastern areas of Santiago (Fig. 1). For each participant, we measured personal, indoor and outdoor PM2.5, PM10 and NO2 concentrations over 24-h periods.
Summary statistics of air pollutant measurements
Descriptive statistics of personal, indoor and outdoor PM2.5, PM10, PM2.5–10 and NO2 concentrations are presented in Table 1.
Mean personal indoor and outdoor PM2.5 concentrations were similar, with values ranging from 68.1 to 69.5 μg/m3 (Table 1). PM10 and PM2.5–10 mean personal exposures were higher than the corresponding indoor and outdoor concentrations. For NO2, mean indoor and outdoor concentrations were comparable and higher than corresponding personal exposures.
The maximum 24-h personal
Discussion
Wintertime particle and NO2 concentrations in Santiago were substantially higher than those reported in US cities. The 24-h outdoor PM2.5 and PM10 concentrations measured in Santiago were 40 and 20% higher than the 12-h daytime levels reported for Riverside, CA (Clayton et al., 1993), and between three- and six-fold higher than those measured over 12 h in Nashville, TN, and Boston, MA (Rojas-Bracho et al., 2000, Bahadori et al., in press). Similarly, in Santiago, ambient NO2 levels were 50%
Acknowledgements
We are grateful to the participants without whom this study would have not been possible; also, we are thankful to D. Belliveau, N. Alba, K. Misra, M. Wolfson, G. Allen, B. Weker, and to the staff working at the Comisión Nacional del Medio Ambiente (CONAMA) and the Servicio de Salud Metropolitano del Ambiente (SESMA) of Santiago, in particular to Y. Silva who coordinated field and laboratory work. We appreciate the feedback from Drs P. Catalano, J. Spengler and T. Smith. This study was funded
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Present address: Comisión Nacional del Medio Ambiente (CONAMA), Santiago, Chile.