An assessment of air pollution and its attributable mortality in Ulaanbaatar, Mongolia

Abstract

Epidemiologic studies have consistently reported associations between outdoor fine particulate matter (PM_2.5) air pollution and adverse health effects. Although Asia bears the majority of the public health burden from air pollution, few epidemiologic studies have been conducted outside of North America and Europe due in part to challenges in population exposure assessment. We assessed the feasibility of two current exposure assessment techniques, land use regression (LUR) modeling and mobile monitoring, and estimated the mortality attributable to air pollution in Ulaanbaatar, Mongolia. We developed LUR models for predicting wintertime spatial patterns of NO₂ and SO₂ based on 2-week passive Ogawa measurements at 37 locations and freely available geographic predictors. The models explained 74% and 78% of the variance in NO₂ and SO₂, respectively. Land cover characteristics derived from satellite images were useful predictors of both pollutants. Mobile PM_2.5 monitoring with an integrating nephelometer also showed promise, capturing substantial spatial variation in PM_2.5 concentrations. The spatial patterns in SO₂ and PM, seasonal and diurnal patterns in PM_2.5, and high wintertime PM_2.5/PM₁₀ ratios were consistent with a major impact from coal and wood combustion in the city's low-income traditional housing (ger) areas. The annual average concentration of PM_2.5 measured at a centrally located government monitoring site was 75 μg/m³ or more than seven times the World Health Organization's PM_2.5 air quality guideline, driven by a wintertime average concentration of 148 μg/m³. PM_2.5 concentrations measured in a traditional housing area were higher, with a wintertime mean PM_2.5 concentration of 250 μg/m³. We conservatively estimated that 29% (95% CI, 12-43%) of cardiopulmonary deaths and 40% (95% CI, 17-56%) of lung cancer deaths in the city are attributable to outdoor air pollution. These deaths correspond to nearly 10% of the city's total mortality, with estimates ranging to more than 13% of mortality under less conservative model assumptions. LUR models and mobile monitoring can be successfully implemented in developing country cities, thus cost-effectively improving exposure assessment for epidemiology and risk assessment. Air pollution represents a major threat to public health in Ulaanbaatar, Mongolia, and reducing home heating emissions in traditional housing areas should be the primary focus of air pollution control efforts.

Keywords: Asia; Coal; Combustion; Exposure; Impact assessment; Nephelometer; Satellite.

Fig. 1

Map of the study area including Ogawa monitoring locations and government-run PM_2.5 monitoring sites

Fig. 2

Monthly distributions of 24-h average a temperature, b PM₁₀, c PM_2.5, d PM_2.5/PM₁₀ ratio, and e SO₂ measured at the Ulaanbaatar City Environmental Monitoring Agency’s site #1 from June 1, 2009 to May 31, 2010

Fig. 3

Diurnal patterns in PM_2.5 concentrations from a June to August and b December to February at the Ulaanbaatar City Environmental Monitoring Agency’s site #1. PM_2.5 concentrations are expressed as the ratio of hourly concentration to average concentration over the 3-month period (June–August average, 23 μg/m³; December–February average, 148 μg/m³)

Fig. 4

LUR model predictions of wintertime a NO₂ and b SO₂ in Ulaanbaatar

Fig. 5

Temporally adjusted light scattering tertiles obtained during mobile monitoring in Ulaanbaatar on a February 24 and 25, 2010 and b February 26, 2010. Approximate PM_2.5 concentrations for each tertile are given in parentheses. For comparison, the mobile data are superimposed on the modeled SO₂ surface shown in Fig. 4b