Alternative ozone metrics and daily mortality in Suzhou: The China Air Pollution and Health Effects Study (CAPES)

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Abstract

Controversy remains regarding the relationship between various metrics of ozone (O3) and mortality. In China, the largest developing country, there have been few studies investigating the acute effect of O3 on death. We used three exposure metrics of O3 (1-hour maximum, maximum 8-hour average and 24-hour average) to examine its short-term association with daily mortality in Suzhou, China. We used a Generalized Additive Model (GAM) with penalized splines to analyze the mortality, O3, and covariate data. We examined the association by season, age group, sex and educational level. We found that the current level of O3 in Suzhou is associated with death rates from all causes and cardiovascular diseases. Among various metrics of O3, maximum 8-hour average and 1-hour maximum concentrations seem to be more strongly associated with increased mortality rate compared to 24-hour average concentrations. Using maximum 8-hour average, an inter-quartile range increase of 2-day average O3 (lag 01) corresponds to 2.15% (95%CI, 0.36 to 3.93), 4.47% (95%CI, 1.43 to 7.51), − 1.85% (95%CI, − 6.91 to 3.22) increase in all-cause, cardiovascular, and respiratory mortality, respectively. The associations between O3 and daily mortality appeared to be more evident in the cool season than in the warm season. In conclusion, maximum 8-hour average and 1-hour maximum concentrations of O3 are associated with daily mortality in Suzhou. Our analyses strengthen the rationale for further limiting levels of O3 pollution in the city.

Highlights

► Controversy remains regarding various metrics of O3 and health hazards. ► Maximum 8-hr average and 1-hr maximum were better health predictors of O3. ► The health impact of O3 was more evident in the cool season in Suzhou.

Introduction

Ozone (O3) is a common urban air pollutant that harms human health (US Environmental Protection Agency, 2006). The health consequences of O3 include increased rates of deaths, hospital admissions and emergency department visits; exacerbation of chronic respiratory conditions; and decreased lung function. Epidemiological and other health studies of O3 use a variety of concentration metrics for the time frame of exposure, including 1-hour maximum, maximum 8-hour average, 8-hour average for a specified time frame (e.g., noon to 8 PM), and 24-hour average. The transition in exposure metrics used in studies and health-based regulation reflects a growing understanding of what exposure time frames best capture the impact of O3 on human health, particularly on lung function. Several studies in developed countries have investigated which ozone metric is most associated with human health response (Abbey and Burchette, 1996).

China, the largest developing country, may have the worst air pollution level in the world (Kan et al., 2009). In Chinese cities, with the rapid increase in the number of motor vehicles, the main air pollution source has gradually changed from conventional coal combustion to mixed coal combustion/motor vehicle emission. O3 is now recognized as an important air pollutant that could increase health risk in China (Kan et al., 2011). To our knowledge, however, few studies have been carried out in China to examine the acute health effects of ambient O3 (Wong et al., 2008).

In the present study, we used three exposure metrics (1-hour maximum, maximum 8-hour average, and 24-hour average) to examine the short-term association between O3 and daily mortality in Suzhou, China. We also examined the modifying effect of season, gender, age and education on the associations between O3 and daily mortality. This study is a component of the China Air Pollution and Health Effects Study (CAPES) (Chen et al., 2011a, Chen et al., 2011b, Chen et al., 2011c).

Section snippets

Data collection

Suzhou, the economic and culture center of Jiangsu Province, is located in the north of the Yangtze River Delta in eastern China (Fig. 1). Our study area was restricted to the urban areas of Suzhou and had a target population of 2.1 million by 2008. We excluded the sub-urban districts due to inadequate air pollution monitoring stations in those areas.

We obtained daily mortality data of urban residents in Suzhou from January 1, 2006 to December 31, 2008 from Suzhou Municipal Center for Disease

Results

From 2006 to 2008 (1096 days), a total of 37,571 deaths (21,551 males and 18,492 females) were registered in the study population. The percentages of total deaths by age group were 1.0% for 0–4 years, 4.8% for 5–44 years, 16.9% for 45–64 years, and 77.3% for ≥ 65 years. On average, there were approximately 33.6 non-accidental deaths per day in Suzhou, including 12.4 from cardiovascular disease and 4.5 from respiratory disease (Table 1). Cardiorespiratory disease accounted for 50.1% of total

Discussion

We found that the current level of O3 in Suzhou is associated with the death rates from all non-accidental causes and from cardiovascular diseases. Among various metrics of O3, 1-hour maximum and maximum 8-hour average seem to be more closely associated with death risk than 24-h average. The association between O3 and daily mortality appeared to be more evident in the cool season than in the warm season. To our knowledge, this is one of the few studies in China to report the acute effect of O3

Conflict of interest

The authors declare that they have no competing financial interests.

Acknowledgments

The study was supported by the National Basic Research Program (973 program) of China (2011CB503802), Gong-Yi Program of China Ministry of Environmental Protection (201209008, 201109064 and 200809109), National Natural Science Foundation of China (30800892), and Program for New Century Excellent Talents in University (NCET-09-0314).

References (32)

  • S. Cakmak et al.

    Do gender, education, and income modify the effect of air pollution gases on cardiac disease?

    J Occup Environ Med

    (2006)
  • R. Chen et al.

    Association of particulate air pollution with daily mortality in the China Air Pollution and Health Effects Study (CAPES)

    Am J Epidemiol

    (2011)
  • J.E. Clougherty

    A growing role for gender analysis in air pollution epidemiology

    Environ Health Perspect

    (2010)
  • L.A. Darrow et al.

    The use of alternative pollutant metrics in time-series studies of ambient air pollution and respiratory emergency department visits

    J Expo Sci Environ Epidemiol

    (2011)
  • R.J. Delfino et al.

    Symptoms in pediatric asthmatics and air pollution: differences in effects by symptom severity, anti-inflammatory medication use and particulate averaging time

    Environ Health Perspect

    (1998)
  • L.J. Folinsbee et al.

    Respiratory responses to repeated prolonged exposure to 0.12 ppm ozone

    Am J Respir Crit Care Med

    (1994)
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    These authors contributed equally to this work.

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