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

doi:10.1016/S0048-9697(01)00987-1

Science of The Total Environment

Volume 287, Issue 3, 27 March 2002, Pages 249-264

https://doi.org/10.1016/S0048-9697(01)00987-1 Get rights and content

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, PM₁₀, respectively), and nitrogen dioxide (NO₂) 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 PM₁₀ 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 NO₂ concentrations were comparable (35.8 and 36.9 ppb) and higher than personal exposures (25.9 ppb). Very low ambient indoor and personal O₃ 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 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 PM_2.5 were close to unity, and for NO₂ they ranged between 0.64 and 0.95. These ratios were probably due to high ambient PM_2.5 and NO₂ levels in Santiago, which diminished the relative contribution of indoor sources and subjects’ activities to indoor and personal PM_2.5 and NO₂ levels.

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 (PM_2.5 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 PM_2.5, PM₁₀, PM_2.5–10, 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 PM_2.5, PM₁₀ and NO₂ concentrations over 24-h periods.

Summary statistics of air pollutant measurements

Descriptive statistics of personal, indoor and outdoor PM_2.5, PM₁₀, PM_2.5–10 and NO₂ concentrations are presented in Table 1.

Mean personal indoor and outdoor PM_2.5 concentrations were similar, with values ranging from 68.1 to 69.5 μg/m³ (Table 1). PM₁₀ and PM_2.5–10 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 PM_2.5 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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¹: Present address: Comisión Nacional del Medio Ambiente (CONAMA), Santiago, Chile.

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

Abstract

Introduction

Section snippets

Methods

Summary statistics of air pollutant measurements

Discussion

Acknowledgements

Environ Int

Environ Int

Toxicol Ind Health

J Expos Anal Environ Epidemiol

The relative contribution of outdoor and indoor particle sources to indoor concentrations

Environ Sci Technol

Ozone, suspended particulates, and daily mortality in Mexico City

Am J Epidemiol

Particle total exposure assessment methodology (PTEAM) study: distributions of aerosol and elemental concentrations in personal, indoor, and outdoor air samples in a Southern California community

J Expos Anal Environ Epidemiol

Analysis of Longitudinal Data

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Annu Rev Public Health

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J Air Pollut Control Assoc

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N Engl J Med

Statistical Methods for Environmental Pollution Monitoring

Aerosol Technology. Properties, Behavior, and Measurement of Airborne Particles

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J Air Waste Manage Assoc

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Am J Epidemiol

Source apportionment of indoor aerosols in Suffolk and Onondaga Counties, New York

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Anal Chem