Elsevier

Environmental Research

Volume 121, February 2013, Pages 52-63
Environmental Research

Size-fractioned particulate air pollution and cardiovascular emergency room visits in Beijing, China

https://doi.org/10.1016/j.envres.2012.10.009Get rights and content

Abstract

Background

Although short-term exposure to ambient particulate matter has increasingly been linked with cardiovascular diseases, it is not quite clear how physical characteristics of particles, such as particle size may be responsible for the association. This study aimed at investigating whether daily changes in number or mass concentrations of accurately size-segregated particles in the range of 3 nm–10 μm are associated with daily cardiovascular emergency room visits in Beijing, China.

Methods

Cardiovascular emergency room visit counts, particle size distribution data, and meteorological data were collected from Mar. 2004 to Dec. 2006. Particle size distribution data was used to calculate particle number concentration in different size fractions, which were then converted to particle mass concentration assuming spherical particles. We applied a time-series analysis approach. We evaluated lagged associations between cardiovascular emergency room visits and particulate number and mass concentration using distributed lag non-linear models up to lag 10. We calculated percentage changes of cardiovascular emergency room visits, together with 95% confidence intervals (CI), in association with an interquartile range (IQR, difference between the third and first quartile) increase of 11-day or 2-day moving average number or mass concentration of particulate matter within each size fraction, assuming linear effects. We put interaction terms between season and 11-day or 2-day average particulate concentration in the models to estimate the modification of the particle effects by season.

Results

We observed delayed associations between number concentration of ultrafine particles and cardiovascular emergency room visits, mainly from lag 4 to lag 10, mostly contributed by 10–30 nm and 30–50 nm particles. An IQR (9040 cm−3) increase in 11-day average number concentration of ultrafine particles was associated with a 7.2% (1.1–13.7%) increase in total, and a 7.9% (0.5–15.9%) increase in severe cardiovascular emergency room visits. The delayed effects of particulate mass concentration were small. Regarding immediate effects, 2-day average number concentration of Aitken mode (30–100 nm) particles had strongest effects. An IQR (2269 cm−3) increase in 2-day average number concentration of 30–50 nm particles led to a 2.4% (−1.5–6.5%) increase in total, and a 1.7% (−2.9–6.5%) increase in severe cardiovascular emergency room visits. The immediate effects of mass concentration came mainly from 1000–2500 nm particles. An IQR (11.7 μg m−3) increase in 2-day average mass concentration of 1000–2500 nm particles led to an around 2.4% (0.4–4.4%) increase in total, and a 1.7% (−0.8–4.2%) increase in severe cardiovascular emergency room visits. The lagged effect curves of number and mass concentrations of 100–300 nm particles or 300–1000 nm particles were quite similar, indicating that using particulate number or mass concentrations seemed not to affect the cardiovascular effect (of particles within one size fraction). The effects of number concentration of ultrafine particles, sub-micrometer particles (3–1000 nm) and 10–30 nm particles were substantially higher in winter comparing with in summer.

Conclusions

Elevated concentration levels of sub-micrometer particles were associated with increased cardiovascular morbidity. Ultrafine particles showed delayed effects, while accumulation mode (100–1000 nm) particles showed immediate effects. Using number or mass concentrations did not affect the particle effects.

Highlights

► Our study was based on accurately size-segregated particles data in a highly polluted megacity (Beijing). ► The effects of particles within different size fractions had different lag patterns.► The lagged effects of ultrafine particles started late and lasted extremely long comparing with results from other studies.► Our study took non-linear exposure-response functions into account.

Section snippets

Background

Ambient particulate matter (PM) has increasingly been linked with cardiovascular diseases during the last decades (Brook et al., 2004). Observed effects of short-term fluctuations of ambient PM on the cardiovascular system include ischemia and arrhythmia in patients with coronary artery disease, altered heart rate and autonomic control, altered blood pressure, systemic inflammatory response, a pro-thrombotic state and endothelial dysfunction (Peters, 2005). The exposure-response functions

Study area and period

We conducted this study in Beijing, China, from 4 Mar 2004 to 31 Dec 2006 (1033 days). Beijing has an area of about 16,808 km2 consisting of eight urban and ten suburban districts (Fig. 1), with a population size of approximately 15,380,000 in 2005 (http://baike.baidu.com/view/2621.htm). It is located in the North China Plain surrounded by mountains of 1000–1500 m in altitude to the west, north, and northeast, and the Bohai Sea on the southeast side. Typical warm temperate semi-humid continental

Cardiovascular emergency room visits data and meteorological data

Table 1 presents the overall cardiovascular emergency room visits counts during the study period, as well as the descriptive statistics for daily total and severe cardiovascular emergency room visits, air temperature, relative humidity, and barometric pressure. Severe cardiovascular emergency room visits counts represented 67% of the total counts. As shown in Supplementary Fig. 1, daily air temperature, relative humidity and barometric pressure all followed seasonal patterns, but with different

Effects of ultrafine particles, sub-micrometer particles and their sub-size fractions

Using particle data from the same measurement station, Breitner et al. (2011) reported 2-days delayed associations between daily cardiovascular mortality in the Beijing urban area and number concentration of Aitken mode particles and particles smaller than 800 nm. In a study conducted in London by Atkinson et al. (2010), the association between particulate number concentration and cardiovascular deaths was observed at lag 1. In studies conducted in Erfurt, Germany, an increase in number

Conclusions

The results from our study add to the evidence that elevated concentration level of sub-micrometer particles are associated with increased cardiovascular morbidity. Ultrafine particles showed delayed effects, while the effects of accumulation mode particles were rather immediate. This might indicate that particles within different size ranges play their effects through different pathways. The different lags by which the effects of certain particle size fractions appear should be considered when

Author contributions

LL performed the statistical analyses and drafted the manuscript. SB and AS guided the statistical analyses and the interpretation of the results, and revised the manuscript critically. JC, AW and BW performed air pollution data collection and data processing, and revised the manuscript critically. IB was involved in the study design and revised the manuscript critically. UF, US, AML and OH were involved in the study design and in air pollution data processing, and revised the manuscript

Acknowledgments

This research was funded by the German Research Foundation (DFG) (grants PE 1156/1–2 and WI 621/16-1). Parts of this work were funded by a scholarship being awarded to Liqun Liu (File no. 2008601213) under the State Scholarship Fund by the China Scholarship Council (CSC). We would like to thank the Emergency Department of Peking University Third Hospital for providing the medical record forms, the Institute for Tropospheric Research (IfT) for providing the monitoring devices, and the State Key

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