The Public Health and Air Pollution in Asia (PAPA) Project: Estimating the Mortality Effects of Particulate Matter in Bangkok, Thailand
Vichit-Vadakan, Nuntavarn, Vajanapoom, Nitaya, Ostro, Bart, Environmental Health Perspectives
BACKGROUND: Air pollution data in Bangkok, Thailand, indicate that levels of particulate matter with aerodynamic diameter [less than or equal to] 10 [micro]m ([PM.sub.10]) are significantly higher than in most cities in North America and Western Europe, where the health effects of [PM.sub.10] are well documented. However, the pollution mix, seasonality, and demographics are different from those in developed Western countries. It is important, therefore, to determine whether the large metropolitan area of Bangkok is subject to similar effects of [PM.sub.10].
OBJECTIVES: This study was designed to investigate the mortality risk from air pollution in Bangkok, Thailand.
METHODS: The study period extended from 1999 to 2003, for which the Ministry of Public Health provided the mortality data. Measures of air pollution were derived from air monitoring stations, and information on temperature and relative humidity was obtained from the weather station in central Bangkok. The statistical analysis followed the common protocol for the multicity PAPA (Public Health and Air Pollution Project in Asia) project in using a natural cubic spline model with smooths of time and weather.
RESULTS: The excess risk for non-accidental mortality was 1.3% [95% confidence interval (CI), 0.8-1.7] per 10 [micro]g/[m.sup.3] of [PM.sub.10], with higher excess risks for cardiovascular and above age 65 mortality of 1.9% (95% CI, 0.8-3.0) and 1.5% (95% CI, 0.9-2.1), respectively. In addition, the effects from [PM.sub.10] appear to be consistent in multipollutant models.
CONCLUSIONS: The results suggest strong associations between several different mortality outcomes and [PM.sub.10]. In many cases, the effect estimates were higher than those typically reported in Western industrialized nations.
KEY WORDS: air pollution, Bangkok, mortality, [PM.sub.10], time series. Environ Health Perspect 116:1179-1182 (2008). doi:10.1289/ehp.10849 available via http://dx.doi.org/ [Online 9 July 2008]
Compelling epidemiologic evidence indicates that current ambient levels of airborne particulate matter (PM) in North American and Western European (NAWE) cities are associated with premature mortality and a wide range of morbidity outcomes [U.S. Environmental Protection Agency (EPA) 2004; World Health Organization (WHO) 2000]. Existing air pollution monitoring information and recent exposure assessments suggest that 6 to 10 million residents of Bangkok, Thailand, are exposed to levels of particulate matter with aerodynamic diameter [less than or equal to] 10 [micro]m ([PM.sub.10]) that are as high as or higher than those in NAWE cities. A recent review of Asian cities, mostly in more developed countries, suggests that PM may also be associated with both mortality and morbidity [Health Effects Institute (HEI) 2004]. However, PM chemical composition and relevant population characteristics, such as activity patterns, background health status, and other factors related to socioeconomic status, may all contribute to differential risks in developing countries such as Thailand. In addition, studies of mortality and air pollution in cities like Bangkok, which have seasonal patterns dramatically different from those of NAWE, provide an opportunity to assess the potentially confounding aspects of seasonality. Bangkok's climate is hot and humid throughout the year, with 24-hr average temperatures almost always above 80[degrees]F. Therefore, with the lack of a cold season, the seasonal weather patterns are very different from those observed in most previous studies.
The question remains whether residents of cities in developing countries are adversely affected by the existing levels of [PM.sub.10] and whether the impacts per unit are similar to those experienced in developed Western countries. Improvements in the mortality data collection system and air monitoring program in Bangkok provide an excellent opportunity to examine the effects of [PM. …