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Table of Contents
RESEARCH ARTICLE
Year : 2018  |  Volume : 3  |  Issue : 2  |  Page : 47-52

Acute effect of air pollutant sulfur dioxide on acute myocardial infarction mortality from 2011 to 2017 in Jinan City


1 Graduate Student, School of Public Health, Shandong University, Jinan, Shandong, China
2 Department of Environmental and Public Health, Jinan Municipal Center for Disease Control and Prevention, Jinan, Shandong, China
3 Graduate Student, School of Public Health, Shandong University; Department of Environmental and Public Health, Jinan Municipal Center for Disease Control and Prevention, Jinan, Shandong, China

Date of Web Publication16-Jul-2018

Correspondence Address:
Liangliang Cui
Department of Environmental and Public Health, Jinan Municipal Center for Disease Control and Prevention, No. 2 Weiliu Road, Jinan, Shandong 250021
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cp.cp_18_18

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  Abstract 


Objectives: The objective of this study is to quantitatively analyze the acute effects of atmospheric pollutant sulfur dioxide (SO2) on acute myocardial infarction (AMI) death in residents of Jinan City. Methods: A descriptive analysis of data on daily weather, air pollutants, and residents' AMI death events was collected from 2011 to 2017 in Jinan city. A generalized additive model (GAM) based on the Quasi-Poisson regression was used to analyze the associations of AMI deaths and SO2. The lag effect of current day (lag0~lag3) and cumulative lagged effect (lag01~lag03) were explored. The excess risk (ER) and 95% confidence interval (CI) of AMI deaths were calculated for every 10 μg/m3 increase in SO2. Results: A total of 40,843 AMI deaths occurred between 2011 and 2017, with a daily average of 16 deaths. During the same period, the average annual value of SO2was 65 μg/m3. An increase in SO2concentration of 10 μg/m3 was associated with an increased risk of death related to AMI at lag 1 by 0.35% (95% CI: 0.06%–0.64%). Especially in cold months, a higher increased risk of 0.49% (95% CI: 0.19%–0.79 %) for AMI death was observed with SO2a 10 μg/m3 increase. While there was a significant cumulative hysteresis effect, the maximum cumulative hysteresis effect appeared in lag 02. Conclusions: The atmospheric pollutant SO2in Jinan City has a significant acute effect on the risk of death from AMI , especially a higher increased risk was observed in cold months.

Keywords: Acute myocardial infarction, air pollution, sulfur dioxide, time-series study


How to cite this article:
Zhang T, Yu K, Zhou L, Cui L. Acute effect of air pollutant sulfur dioxide on acute myocardial infarction mortality from 2011 to 2017 in Jinan City. Cardiol Plus 2018;3:47-52

How to cite this URL:
Zhang T, Yu K, Zhou L, Cui L. Acute effect of air pollutant sulfur dioxide on acute myocardial infarction mortality from 2011 to 2017 in Jinan City. Cardiol Plus [serial online] 2018 [cited 2018 Aug 17];3:47-52. Available from: http://www.cardiologyplus.org/text.asp?2018/3/2/47/236820




  Introduction Top


Cardiovascular disease (CVD) is the leading cause of death and disability worldwide. The World Health Organization (WHO) reported that about 17.5 million people died of CVD in 2012, accounting for 31% of the global death toll.[1] It is estimated that by 2020, more than 80% of the world's CVD will occur in low- and middle-income countries, with China and India likely to have the largest disease burden.[2] In China, CVD is currently the leading cause of death, accounting for about 43% of the total deaths.[3] Those ≥40-year-old make up the key population at increased risk of death from cardiovascular disease and acute myocardial infarction (AMI).[4] Sulfur dioxide (SO2) is a colorless gas and is one of the main pollutants in the atmosphere. It is mainly produced from the combustion of sulfur-containing mineral fuels, such as coal and oil (about 80%) and is also a by-product of the process of smelting and conversion of nonferrous metals.[5] The most well-known SO2 pollution incident was the London fog incident. As a result of the inversion of temperature, carbon dioxide, carbon monoxide, SO2, dust, and other gases and pollutants emitted from coal-fired power plants and homes accumulated over the city. The concentration of soot and SO2 were 10 times and 6 times higher than usual, respectively. Deaths from bronchitis, coronary heart disease, tuberculosis, and heart failure during this incident were 9.3 times, 2.4 times, 5.5 times and 2.8 times higher than the week before the event. The number of chronic deaths was 8000, 5 times greater than average. Compared with the same period of the previous year, the number of excess deaths was 3000–4000.[6],[7]

The in-depth study of global air pollution has been the focus of current research. A large number of epidemiological studies have reported the acute effects of short-term exposure to air pollutants (such as SO2, PM2.5, O3, and NO2) on cardiovascular and respiratory diseases (including acute effects of morbidity and mortality).[8],[9],[10] Specifically, scholars have reported the acute effects of air pollutants on hypertension,[11] ischemic heart disease,[12] heart failure,[13] and AMI.[14]

In recent years, the air pollution problem in China has attracted worldwide attention. Since 2011, severe haze events have frequently occurred in Northern China, especially during the cold season. Central heating is frequently used for 5 months of the year,[15] and atmospheric particulates and SO2 concentrations in gaseous combustion products increase significantly during this period.[16],[17],[18] The acute effects of atmospheric particulates (PM2.5, PM10) on cardiovascular diseases in Chinese cities have been widely reported,[19],[20],[21],[22],[23] but research investigating the acute effects of SO2 is rather limited. There is also a lack of understanding of the acute effects of SO2 and cardiovascular diseases during heating season. For this reason, this study selected Jinan City, a typical Northern heating city in China, to carry out acute health risk studies on the risk of air pollutant SO2 and AMI death in this population. During 2011 and 2017, a total of 40,843 people died of AMI in Jinan.


  Methods Top


Jinan, as a large urban city in the Eastern China, has a resident population of about 700,000. It is located at 36.40°N latitude and 110.00°E longitude, and covering an area of 8227 km 2. It is a warm temperate continental monsoon climate with clear seasons, hot summers and cold winters. Typical industries, including a central heating power plant, machinery manufacture, textile and steel production, chemical manufacturing, light industry, food processing industry, and building materials industry contributed to nearly 40% of the gross domestic product in Jinan.[24]

Air pollution and meteorological data

Daily mean hourly air pollutant concentration data (inhalable SO2 and PM2.5) and daily maximum of 8-hourly running mean of O3 were obtained from Jinan Environmental Monitoring Center from January 1, 2011 to December 31, 2017. The data were obtained from 14 fixed monitoring stations, covering the entire region of Jinan. Daily average values of air pollution were used in this study and calculated from the above 14 fixed monitoring stations. Daily weather information for the same period was collected from the China Meteorological Science Data Sharing Service Network (http://cdc.cma.gov.cn/home.do). The following weather data was downloaded: Daily average temperature (°C), daily maximum temperature (°C), daily minimum temperature (°C), and daily average relative humidity (RH) (%).

Mortality data

A total of 40,843 AMI-related deaths were derived from Jinan Municipal Center for Disease Control and Prevention. They were categorized as I21 according to the International Classification of Diseases, 10th Revision.

Statistical analysis

A generalized additive model based on Quasi-Poisson regression was used to analyze the correlation between daily AMI deaths and atmospheric pollutant Zt (SO2). The natural spline smoothing function (ns) was used to fit the long-term and seasonal trends of the time series, with a df of 7/year.[25] In the model, the cubic spline smoothing function(s) was used to control the confounding effects of the daily average temperature (temp) and daily average RH of meteorological factors, and the df were all chosen to be 3.[26] The day-of-the-week effect (DOW) and holiday effect (Holiday) were included in the model as categorical variables.

See the following Formula 1 for the model:



The lag effects of current day (lag0-lag3) and cumulative days (lag01-lag03) for AMI deaths with SO2 per 10 μg/m 3 increase were estimated. We calculated the excess risk (ER) and 95% confidence interval (95% CI) for AMI deaths per 10 μg/m 3 increase in the SO2 concentration and used the maximum effect value as the exposure risk estimate. The stratified analysis of atmospheric pollutants SO2 and daily AMI was further carried out in the cold months (October-April) and warm months (May-September) separately.[14],[17],[25]

Sensitive analysis

Three types of sensitivity analyses were performed when the resident mortality risk of AMI was at its maximum (lag 2): (a) The df of the time trend in the change model was from 5 to 9, compared with the results of the main model (df = 7); (b) the two-pollutant models were analyzed, and PM2.5 and O3 were added to the main model, respectively; (c) In the main model, the daily maximum temperature and the daily minimum temperature were used to replace the daily average temperature indicators. The results were compared with the main model.

All statistical analyses were conducted using R software (version 3.3.2, http://www.r-project.org/). P < 0.05 was considered statistically significant.


  Results Top


Description analysis

[Table 1] describes the distribution of AMI deaths and air pollution and meteorological factors in Jinan City from January 1, 2011 to December 31, 2017. A total of 40,843 cases of AMI died, with a daily average of 16 deaths (range: 3–48). The average number of deaths per day in the cold and warm months was 18 (range: 4–48) and 13 (range: 3–41) people. During the 7-year period, the annual average values of SO2, PM2.5, and O3 were 65, 90 and 102 μg/m 3, respectively. [Figure 1] shows the day-to-day AMI and SO2 concentration distributions, both showing significant seasonal trends and consistency; the daily mean value of SO2 in the cold months was 83 μg/m 3, which was significantly higher than during the warm months (40 μg/m 3; P < 0.001).
Table 1: Daily acute myocardial infarction mortality and environmental indicators 2011-2017, Jinan city

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Figure 1: Daily acute myocardial infarction mortality and sulfur dioxide 2011–2017, Jinan city

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Acute effects of sulfur dioxide and acute myocardial infarction

Lag effects of current day

[Table 2] shows the associations of SO2 and AMI mortality. An increased risk of 0.35% (95% CI: 0.06%–0.64%) was showed for AMI mortality at lag1 with SO2a 10 μg/m 3 increase. In cold months, for each 10μg/m 3 increase in SO2, the AMI deaths will increase 0.49% (95% CI: 0.19%–0.79%) at lag 1. No significant effects of SO2 and AMI mortality were found during the warm months.
Table 2: The associations of sulfur dioxide on daily acute myocardial infarction mortality 2011-2017, Jinan city

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Lag effects of cumulative days

The maximum cumulative hysteresis effect of SO2 on AMI mortality occurred in lag 02 and the ER was 0.56% (95% CI: 0.16%–0.96%) and 0.81% (95% CI: 0.40%–1.22%), respectively, in the whole year and during cold months alone. No significantly cumulative lag effects of SO2 and AMI mortality in warm months was found.

Sensitive analysis

[Figure 2] shows the results of sensitivity analysis of SO2 and AMI mortality. [Figure 2]a shows the sensitivity analysis of the time-degree-of-freedom (df) from 5 to 9. The results of the main model analysis (df = 7) and the different df had less variation, suggesting that the main model results are stable. [Figure 2]b shows the results of the dual-contamination model analysis. After adding the PM2.5 and O3 in the main model separately, the results still had small changes. [Figure 2]c shows results after adding the highest temperature on the day and the lowest temperature on the day in the main model. It also indicated the robustness of the main model fitting.
Figure 2: Sensitive analysis of daily sulfur dioxide and acute myocardial infarction mortality. (a) Sensitivity analysis of time-degree-of-freedom transformation (b) Sensitivity analysis of dual-pollutant model (c) Sensitivity analysis of temperature index transformation

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  Discussion Top


In this study, time series analysis were used to quantitatively assess the exposure response of air pollutant SO2 and AMI deaths in Jinan during the period of 2011–2017. This was the first study investigating the acute effect of atmospheric pollutant SO2 and AMI deaths in Jinan City. The 7-year time series analysis showed that there was a significant acute effect between atmospheric pollutant SO2 and AMI death. In the whole year and in cold months alone, for every 10 μg/m 3 increase of atmospheric pollutant SO2 concentration, the risk of death from AMI increased by 0.35% (95% CI: 0.06%–0.64%) and 0.49% (95% CI: 0.19%–0.79%), respectively. There was also a significant cumulative hysteresis effect. Cold months had an effect that lasted longer and the maximum effect value appeared in lag 02, suggesting that the cold months are a high-risk season.

The SO2 monitoring results for 7 consecutive years showed that the average annual SO2 concentration in Jinan City was 65 μg/m 3, which was more than 8.3% of the secondary standard (60 μg/m 3) of the Ambient Air Quality Standard (GB 3095-2012).[27] It was higher than the annual SO2 average concentration (40.4 μg/m 3) in 107 cities in Northern China reported by Wang et al.,[18] and 49 μg/m 3 in Tianjin conducted by Guo et al.[28] However, it was lower than the annual average concentration of SO2(79.11 μg/m 3)[29] reported by Zheng et al. in the study of Lanzhou, and lower than the average annual concentration of SO2 (197 μg/m 3) in the study of Shenyang conducted by Zhao et al.[23] The results of this study showed that the SO2 concentration in the cold months increased significantly and was significantly higher than the warm months. This trend was related to the central heating used during cold months in Northern cities of China. SO2 is mainly produced by the combustion of sulfur-containing fossil fuels such as coal and oil (about 80%), and in Northern China, winter heating predominantly uses coal combustion, significantly increasing SO2 concentration during the cold months.

There are a few existing studies focusing on the effects of multiple air pollutants and CVD admissions or deaths, which quantitatively measure the acute effects of air pollutants (such as SO2, PM2.5, CO, and NO2) with cardiovascular disease/death. A study by Li et al.[30] in Ningbo found that the risk of cardiovascular death increased by 4.90% (95% CI: 0.10%–9.80%) when the concentration of SO2 increased by 10 μg/m 3. A study by Liu et al.[31] in Wuhan found that for every 10 μg/m 3 increase in SO2 concentration, the risk of CVD death increases by 1.00% (95% CI: 0%–2.00%). The above studies have shown that short-term exposure to SO2 has an acute effect on death due to cardiovascular diseases, but there are few reports on the impact of air pollutants on the death of specific cardiovascular system diseases, including AMI.[32],[33] This study quantitatively analyzed the acute effects of short-term exposure to SO2 on AMI-related deaths and enriched the evidence for the relationship between air pollutant SO2 and AMI deaths. This study found that the risk of AMI increased by 0.35% (95% CI: 0.06%–0.64%) when the SO2 concentration of air pollutants increased per 10 μg/m 3 at lag 1. The results of Abdolahnejad et al.[32] on Isfahan showed that for every 10 μg/m 3 increase in SO2 concentration, the risk of death from AMI increased by 0.64% (95% CI: 0.26%–1.00%). The results of Sharovsky et al.[33] on São Paulo showed that for every 10 μg/m 3 increase in SO2 concentration, the risk of death from AMI could be increased by 3% (95% CI: 2%–5%). Our research results are lower than those of the above two studies. The present study also analyzed the cumulative hysteresis effect of SO2 on the death of acute myocardial infarction. It was found that the duration of the effect of SO2 on the death of AMI can reach 6 days, and the maximum effect value appeared in lag 02, where the ER was 0.81% (95% CI: 0.40%–1.22%).

This study found that in the cold months, the acute effects of SO2 on AMI were greater, and the duration of these effects was longer. For every increase in concentration of pollutants by 10 μg/m 3, SO2 increased the risk of death from AMI by 0.49% (95% CI: 0.19%–0.79%). In cold months, due to coal-fired heating [16],[17] and other reasons, SO2 emissions from atmospheric pollutants increased and concentrations rose sharply. Therefore, the acute effects of SO2 on AMI deaths also increased. This finding is consistent with the conclusions of air pollution and death research conducted by Zhang et al.[17] in Jinan City from 2011 to 2015.

By performing the sensitivity analysis of the variation of the time trend, the double-pollutant model, and the change of different temperature indexes in the main model, we confirmed that that the main model was well fitted and the results were robust. However, this study still has the following limitations:First, the average values of the 14 air pollutant monitoring sites in the city was used rather than individual exposure levels in patients suffering AMI deaths. Second, due to the limited number of deaths per day in acute myocardial infarction, no analysis of acute effects by gender or age group was conducted. However, significant acute effects of atmospheric pollutant SO2 and death from AMI were still observed in this study.


  Conclusions Top


This study is the first report on the effect of SO2 on death by AMI in China in recent years. It is the first report of this kind of research in Northern cities of China, which further enriches the content of current research on the impact of air pollution on the health of the population. It also provides a technical basis for the local air pollution health management and policy designation.

Acknowledgments

This work was funded by grants from the Medicine and Technology Development Plan Project of Shandong Province (2015WS0435).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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