Elsevier

Environmental Research

Volume 140, July 2015, Pages 684-690
Environmental Research

Effects of ambient air particles on mortality in Seoul: Have the effects changed over time?

https://doi.org/10.1016/j.envres.2015.05.029 Get rights and content

Highlights

  • We explored time-varying short-term effect of PM on mortality in Seoul, Korea.

  • PM mass concentration drastically decreased over time.

  • The effect size of PM on mortality may increase over time.

  • The toxicity of PM or bias in time-series analysis may change over time.

  • Air quality policies may not play desirable role in reducing health risks as expected.

Abstract

Background

Several studies have shown that there may be temporal variation in PM short-term effect on mortality. This temporal pattern may play an important role in evaluating air quality policies.

Objectives

We investigated temporal variation in the association between PM and mortality in Seoul, Korea, 1998–2011.

Methods

We adopted a generalized additive model and a series of time windows of five years to analyze temporal variation in associations between PM and all-cause, cardiovascular, and respiratory mortality. This time-window approach offers not only a comparison between one and the other half period but also successive variation. Time-varying associations were estimated only for days without Asian dust (dust storm blown from the Gobi desert) intrusion.

Results

Annual average PM10 and PM2.5 total mass decreased from 70.0 to 46.9 µg/m3 and 44.4 to 23.4 µg/m3, respectively, during 2001–2011. A 10 µg/m3 increase in PM10 was associated with 0.16% (95% CI=−0.03% to 0.35%) additional all-cause deaths in 2002–2006 and it increased to 0.26% (95% CI=0.05–0.48%) in 2007–2011. For PM2.5, the association increased from 0.35% (95% CI=−0.02% to 0.71%) to 0.48% (95% CI=0.08–0.88%). For cardiovascular and respiratory mortality, increasing trends with stronger estimates were found.

Conclusions

The present study showed temporally increasing trends in associations between PM and mortality. Current policies may not be as effective to reducing health risks attributable to PM as expected. Air quality interventions should be encouraged in terms of causal factors for time-varying association between PM and mortality.

Introduction

Epidemiological research has demonstrated that acute exposure to particulate matter with an aerodynamic diameter <10 µm (“PM10”) is associated with diverse health response (Pope III and Dockery, 2006). Incorporating advanced measurement technologies, researchers have since then concentrated on smaller particles, with aerodynamic diameters <2.5 µm (“PM2.5”) and provided consistent evidence of a stronger association with health outcomes than that of PM10 or PM10–2.5 (Dong et al., 2013, Schwartz and Neas, 2000). In Seoul, the capital of South Korea, many studies have reported an association between short-term exposure to PM and an increase in risk of health outcomes (Heo et al., 2014, Lee et al., 2007, Son et al., 2012).

“Asian dust,” also known as yellow dust, which originates in the Gobi Desert spread from Southern Mongolia to Northern China, is sporadically blown to Korean peninsula by westerly winds and aggravates air quality in the region. It leads to increase particulate concentrations, but especially tends to increase coarse particles with crustal components (Kim et al., 2003). In fact, such particles may be less deleterious to human health than fine particles (Pope III and Dockery, 2006). Thus, an association of particulates with mortality regardless of excluding days with Asian dust intrusion in a statistical model would possibly be underestimated in terms of PM effects for dominant non-Asian dust days (Lee et al., 2007). Accordingly, it is necessary to take this concept into account when analyzing PM effects on mortality in Korea.

According to recent studies, there may be temporal variation in short-term effects of air pollution; the relative risk is not constant over time. Studies in the U.S. and Europe found decreasing patterns in PM effects over time (Breitner et al., 2009, Dominici et al., 2007). They suggested that air quality control policies may have had an impact on not only reducing PM mass concentration but also on desirable changes in the constituents of PM. If there are similar trends in Korea, a time-varying effect of PM may also be expected.

Thus, we sought to analyze an association between PM and mortality in Seoul, considering the intrusion of Asian dust. Second, we investigated temporal variation in the association, and suggested possible reasons for a time-varying effect of PM on mortality. Finally, we made suggestions on future studies and ambient air quality policies.

Section snippets

The scope and data

The study location was Seoul, Korea, with a population of about 10 million (Statistics Korea, 2010). Data for mortality, PM10, PM2.5, and meteorological factors were obtained from Statistics Korea, the National Institute of Environmental Research, Seoul Metropolitan Government Research Institute of Public Health and Environment, and the Korea Metrological Administration, respectively.

PM concentration in Seoul has been measured in national monitoring stations since 1995 for PM10 and 2001 for PM

Descriptive statistics

Regardless of Asian dust intrusion, the average daily PM10 concentration for the study period, 1998–2011, was 60.7 µg/m3. For PM2.5, it was 32.1 µg/m3 in 2001–2011. There were a total of 159 Asian dust days. Average concentrations of PM10 and PM2.5 were higher during Asian dust intrusion in the corresponding periods (Table 1). Annual ambient PM concentrations have declined consistently (Fig. 1)

The average daily all-cause mortality was 93.3. Death count in those aged 65 years or older (65+)

Discussion

In this study, we found that association of PM with mortality was enlarged when excluding days with Asian dust intrusion. These results were consistent with the previous study suggesting that increased PM concentration attributable to Asian dust intrusion contributed relatively less toxic particles fraction, so that it may cause underestimated risks of PM (Lee et al., 2007). Also, it was pointed out that recognition of an Asian dust event may change individual behavior to minimize exposure to

Conclusion

In this study, we found that adverse effects of PM on mortality may increase over time in Seoul, Korea. In addition, unawareness of Asian dust intrusion in a statistical analysis may cause underestimation of PM effect on mortality in non-Asian dust period. To elucidate temporal variation in PM effect, we generated hypotheses on increase in fraction of toxic constituents within PM and decrease in representativeness of population average ambient PM to individual exposure to ambient-origin PM in

Acknowledgments

This work was financially supported by the National Research Foundation of Korea Grant (2014R1A2A1A11052556) funded by the Korea government (MSIP).

References (33)

  • E. Diapouli

    Estimating the concentration of indoor particles of outdoor origin: a review

    J. Air Waste Manag. Assoc.

    (2013)
  • F. Dominici

    Particulate air pollution and mortality in the United States: did the risks change from 1987 to 2000?

    Am. J. Epidemiol.

    (2007)
  • F. Dong

    Association between ambient PM10/PM2.5 levels and population mortality of circulatory diseases: a case-crossover study in Beijing

    Beijing da xue xue bao. Yi xue ban=J. Peking Univ. Health Sci.

    (2013)
  • T. Godish

    Indoor Air Pollution Control

    (1989)
  • J. Heo

    Fine particle air pollution and mortality: importance of specific sources and chemical species

    Epidemiology

    (2014)
  • A. Ibald-Mulli

    Epidemiological evidence on health effects of ultrafine particles

    J. Aerosol Med.

    (2002)
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