Differentiating the effects of characteristics of PM pollution on mortality from ischemic and hemorrhagic strokes

doi:10.1016/j.ijheh.2015.11.002

International Journal of Hygiene and Environmental Health

Volume 219, Issue 2, March 2016, Pages 204-211

https://doi.org/10.1016/j.ijheh.2015.11.002 Get rights and content

Abstract

Though increasing evidence supports significant association between particulate matter (PM) air pollution and stroke, it remains unclear what characteristics, such as particle size and chemical constituents, are responsible for this association. A time-series model with quasi-Poisson function was applied to assess the association of PM pollution with different particle sizes and chemical constituents with mortalities from ischemic and hemorrhagic strokes in Guangzhou, China, we controlled for potential confounding factors in the model, such as temporal trends, day of the week, public holidays, meteorological factors and influenza epidemic. We found significant association between stroke mortality and various PM fractions, such as PM₁₀, PM_2.5 and PM₁, with generally larger magnitudes for smaller particles. For the PM_2.5 chemical constituents, we found that organic carbon (OC), elemental carbon (EC), sulfate, nitrate and ammonium were significantly associated with stroke mortality. The analysis for specific types of stroke suggested that it was hemorrhagic stroke, rather than ischemic stroke, that was significantly associated with PM pollution. Our study shows that various PM pollution fractions are associated with stroke mortality, and constituents primarily from combustion and secondary aerosols might be the harmful components of PM_2.5 in Guangzhou, and this study suggests that PM pollution is more relevant to hemorrhagic stroke in the study area, however, more studies are warranted due to the underlying limitations of this study.

Introduction

A great number of epidemiological studies have demonstrated a consistent increased risk from stroke with short term exposure to ambient particulate matter (PM) air pollution, which was generally measured as particulate matter with aerodynamic diameter ≤10 μm (PM₁₀) or ≤2.5 μm (PM_2.5) (Dominici et al., 2006, Williams et al., 2014). Previous studies mainly evaluated the relationship of stroke occurrence with total mass concentration of the particles, fewer have examined the stroke effects of different characteristics of the particles, such as particle size and their chemical constituents (Kettunen et al., 2007), and more importantly limited studies have been conducted to differentiate the effects of these PM characteristics on different stroke types, which presented an obstacle to a better understanding of the biological mechanisms of their association.

Epidemiological and toxicological studies suggest that smaller particles might be more harmful to human health (Lin et al., 2015). Only limited epidemiological studies, however, have examined the association between stroke and these smaller particles with inconsistent findings. For example, a study examined the relationship between stroke mortality and three size fractions (PM_2.5–10, PM_1–2.5 and PM₁) in Barcelona, Spain, and found that PM₁ and PM_2.5–10, rather than PM_1–2.5, was associated with stroke mortality (Perez et al., 2009). A study from Helsinki, Finland only detected significant stroke effects of PM_2.5 and ultrafine particles (PM_0.1) in warm season, but not in cold season (Kettunen et al., 2007). And in Copenhagen, Denmark, ultrafine particle, rather than PM₁₀, was found to be associated with ischemic stroke hospitalization without atrial fibrillation (Andersen et al., 2010). One recent systematic review suggested that PM_2.5 and PM₁₀, rather than PM_2.5–10, were associated with stroke mortality (Wang et al., 2014).

On the other hand, the current air pollution control guidelines/regulations generally use total mass concentration as the indicator. Although it is important to protect human health, more targeted air quality standards need to incorporate PM chemical constituents or emission sources that are more directly related to the health impacts, and this has been viewed as the ultimate goal of air pollution control policies. However, such standards have been hindered by limited information on the toxicity of PM constituents (Dai et al., 2014). PM consists of many chemical components that originate from different sources, such as industrial emission, traffic, biomass burning and coal combustion. Exploring which specific PM component was associated with a given health outcome will also help to explain the underlying mechanism of the PM health effects (Li et al., 2014).

The objective of this study was to investigate the relationship between PM pollution with different particle sizes (PM₁₀, PM_2.5–10, PM_2.5, PM_1–2.5 and PM₁), PM_2.5 constituents and mortalities from ischemic and hemorrhagic strokes in Guangzhou, China.

Section snippets

Study setting

Guangzhou, the capital city of Guangdong Province, is an economic center of south China. Due to the rapid economic development and corresponding rise in energy consumption over the past decades, this city has experienced serious air pollution. Guangzhou has a typical subtropical humid-monsoon climate with an average annual temperature of 22 °C and average rainfall of 1500–2000 mm. The residents in urban districts of Guangzhou were selected as the subjects of this study, with a population of about

Results

From 1st January 2007 to 31st December 2011, we recorded a total of 9066 stroke deaths, the corresponding annual stroke mortality rate was 33.21 per 100,000 population. Of them, 5113 were ischemic stroke and 3953 were hemorrhagic stroke. On average, there were 5.0 stroke deaths per day (Table 1).

During the period of 2009–2011, daily concentrations of PM₁₀, PM_2.5–10, PM_2.5, PM_1–2.5 and PM₁ in Guangzhou were 56.0, 14.6, 41.4, 4.4 and 37.0 μg/m³, respectively (Table 1). PM_2.5 accounted for a

Discussion

There has been limited information on the association between characteristics of PM pollution and stroke mortality (Kettunen et al., 2007). To our knowledge, this might be the first study to simultaneously quantify the effects of particle size and chemical constituents of PM pollution on stroke mortality. We found a significant association between stroke mortality and PM₁₀, PM_2.5 and PM₁, and we found that PM_2.5 chemical constituents, mainly combustion-related and secondary particle components,

Conclusion

In summary, the present study suggests particle size and chemical composition might be important determinant of the association between PM pollution and stroke mortality, and this study suggests that PM pollution might be more relevant to hemorrhagic stroke in the study area, however more studies are warranted due to the underlying limitations of this study.

Conflict of interest

None.

Acknowledgments

We sincerely thank those who participated in data collection and management of this study. This study was supported by Guangdong Medical Research Foundation (B2013077).

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Differentiating the effects of characteristics of PM pollution on mortality from ischemic and hemorrhagic strokes

Abstract

Introduction

Section snippets

Study setting

Results

Discussion

Conclusion

Conflict of interest

Acknowledgments

Environ Int.

Environ. Res.

Lancet

Atmos. Res.

Sci. Total Environ.

Atmos. Environ.

Association between short-term exposure to ultrafine particles and hospital admissions for stroke in Copenhagen, Denmark

Eur. Heart J.

Size distribution and total number concentration of ultrafine and accumulation mode particles and hospital admissions in children and the elderly in Copenhagen, Denmark

Occup. Environ. Med.

Impact of fine and ultrafine particles on emergency hospital admissions for cardiac and respiratory diseases

Epidemiology

Air pollution and cardiovascular disease: a statement for healthcare professionals from the expert panel on population and prevention science of the American Heart Association

Circulation

Fine particulate matter constituents and cardiopulmonary mortality in a heavily polluted Chinese city

Environ. Health Perspect.

Acute effect of ambient air pollution on stroke mortality in the china air pollution and health effects study

Stroke

Associations of fine particulate matter species with mortality in the United States: a multicity time-series analysis

Environ. Health Perspect.

Fine particulate air pollution and hospital admission for cardiovascular and respiratory diseases

J. Am. Med. Assoc.

Daily mortality and air pollution in Santa Clara County California: 1989–1996

Environ. Health Perspect.

Mortality and air pollution for Santa Clara county. California, 1989–1996

Revised Analyses of Time-series Studies of Air Pollution and Health. Special report

Air pollution and ST-segment depression in elderly subjects

Environ. Health Perspect.

Aerosol measurement: the use of optical light scattering for the determination of particulate size distribution, and particulate mass, including the semi-volatile fraction

J. Air Waste Manag. Assoc.

Repolarization changes induced by air pollution in ischemic heart disease patients

Environ. Health Perspect.