Air Pollution and Cardiovascular Mortality in Kerman from 2006 to 2011

Hashemi S.Yaser, Khanjani Narges, Soltaninejad Yaser, Momenzadeh Rasoul

  Open Access OPEN ACCESS  Peer Reviewed PEER-REVIEWED

Air Pollution and Cardiovascular Mortality in Kerman from 2006 to 2011

Hashemi S.Yaser1, Khanjani Narges2,, Soltaninejad Yaser1, Momenzadeh Rasoul1

1Department of Environmental Health, Faculty of Public Health, Kerman Medical University, Kerman, Iran

2Department of Epidemiology and Dept of Environmental Health, Faculty of Public Health, Kerman Medical University, Kerman, Iran

Abstract

Air pollution is one of the problems in major world cities that endanger the health of the inhabitants of these cities. Air pollution may cause increased death from cardiovascular diseases. This study was carried out in Kerman, Iran. Data about cardiovascular mortality was inquired from the Kerman city Health Authority and air pollution data was inquired from the Kerman Environmental Protection Agency from 2006 to 2011. The concentration of seven pollutants SO2, NO2, O3, CO, PM10, NOX NO, is measured daily in Kerman. The relation between mortality from cardiovascular diseases and air pollution was analyzed by using correlation and negative binomial regression. Statistical analysis showed that the only significant correlation observed was between ozone and female cardiovascular mortality (r = 0.31). With increase in ozone, the number of female cardiovascular deaths increased as well. But in both crude and adjusted negative binomial regression increase in pollutants was not associated with increased incidence of cardiovascular deaths. There was not a significant relation between air pollution and cardiovascular death in Kerman. More studies in cities with higher levels of pollutants are needed to assess the effects of pollutants on cardiovascular mortality.

Cite this article:

  • S.Yaser, Hashemi, et al. "Air Pollution and Cardiovascular Mortality in Kerman from 2006 to 2011." American Journal of Cardiovascular Disease Research 2.2 (2014): 27-30.
  • S.Yaser, H. , Narges, K. , Yaser, S. , & Rasoul, M. (2014). Air Pollution and Cardiovascular Mortality in Kerman from 2006 to 2011. American Journal of Cardiovascular Disease Research, 2(2), 27-30.
  • S.Yaser, Hashemi, Khanjani Narges, Soltaninejad Yaser, and Momenzadeh Rasoul. "Air Pollution and Cardiovascular Mortality in Kerman from 2006 to 2011." American Journal of Cardiovascular Disease Research 2, no. 2 (2014): 27-30.

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1. Introduction

Cardiovascular diseases are equally prevalent in men and women and lead to one the most prevalent and important cause of mortality. Studies demonstrate that cardiovascular diseases are the cause of one third of human death in the world [1]. These diseases are the main cause of disability and morbidity and impose a great financial burden on the governments [2, 3]. Myocardial Infarction is one of the most significant cardiovascular diseases. In Iran in the past its prevalence was higher among the 40 to 70 years old, but has now increased among the 20 to 60 years old during the last several years [2]. Cardiovascular diseases are the second main cause of mortality in Iran after accidents [2, 4]. Various factors are involved in the incidence of these diseases including low physical activity, stress, a positive family history, smoking, hypertension, hyperlipidemia, and probably air pollution [1, 5, 6].

Nowadays, air pollution is proposed as one of the main problems in urban and industrial life [7]. Based on the World Health Organization’s report, at the beginning of the 21th century more than 200 million people in the world were exposed to air pollutant concentrations higher than air quality standards [8]. With the progress of industry and invention of cars, nowadays 80 percent of air pollution is allocated to vehicles [9]. Using fuel with low quality, vehicle technical defects, low education, lack of public participation in pollution prevention plans, migration to cities, and lack of coordination between legislator and executive systems has contributed to the ascending trend in air pollution [6, 9]. Pollutants such as carbon monoxide, hydrocarbons, nitrogen dioxide, sulfur dioxide, particulates, and ozone have the most proportion in air pollution [9, 10]. Each of these pollutants may have unfavorable and negative effects on humans. Their main effect on the human body is on the respiratory and circulatory systems [1]. These pollutants in various concentrations threaten the life of cardio-pulmonary patients, aged people, infants, and pregnant women and also can contribute to tension, vertigo, headache, and fatigue in healthy people [10].

The cardiovascular diseases related to mortality due to the exposure of the pollutants is elicited can be due to myocardial infarction andarrhythmias. Nowadays, in developing countries, strict environmental legislation partially contribute to controlling air pollution but due to changing of life styles from traditional to industrial, and lack of appropriate control on pollutant resources, air pollution has had an ascending trend. One of these countries is Iran which is placed as one of the most polluted cities in the world based on the 2011 WHO report [11].

Kerman is located in the southeast of the Central Iran Plateau with 1756 meters height from sea level, mean temperature of 15.8 C˚, and average annual rainfall of 155 mm. Kerman’s area is 14000 hectares and is categorized as one of metropolises on Iran due to its’ area and population. Based on the last census in 2011, the city of Kerman has a population of more than 534,441 [12, 13]. The main pollutant sources in this city include various industries and factories. On the other hand, increasing number of cars and vehicles is one of the reasons for air pollution in this city. Furthermore, the entry of dusts originating from surrounding deserts exacerbates air pollution in this city in some months of the year [12].

There has been no epidemiological study regarding the relationship between air pollution and cardiovascular disease mortality in Kerman and due to the unique climatic, weather, and cultural characteristics of this city, the importance of such a study is felt more than ever. The aim of this study was to determine the relationship between air pollution and cardiovascular mortality rate in the city of Kerman.

2. Methodology

This retrospective ecological study was carried out in the city of Kerman. In this study, all mortality rates due to cardiovascular diseases in the city of Kerman during the study period (2006 to 2011) was collected from the Kerman city health authorities and then cardiovascular mortality cases were extracted. Data related to air pollution was inquired from the Kerman Environmental Protection Agency. The concentration of 7 pollutants including SO2, NO2, O3, CO, PM10, NOX, and NO are measured daily in Kerman by fixed stations.The urban monitoring stations in Kerman used the method of Beta-ray absorption for measuring the concentration of PM10,UV fluorescencefor SO2, Chemical luminance for NO, NO2 and NOX, Non Diffraction Infrared Absorption (NDIR) for CO and UV absorption for measuring the concentration of O3.

The 24-hour standard of pollutants according to AQI’s 24-hour standard for CO and PM10 is listed in Table 1.

Table 1. The 24-hour standard for pollutants based on the AQI’s 24-hour standard for CO and PM10

In this study, all deaths due to cardiovascular diseases in each month were determined, and then were matched with air pollution data. The relationship between mortality rate and air pollution was assessed through correlation and negative binomial regression. All statistical analyses were done using SPSS 19.

3. Results of the Study

The descriptive statistics of air pollutants during these 6 years are listed in Table 2. The overall mortality count due to cardiovascular disease in each month during these 6 years is demonstrated in Table 2.

Table 2. Descriptive indices of air pollutants in the city of Kerman from March 2006 to March 2011

Table 3. The overall mortality due to cardiovascular diseases in each month in the city of Kerman from March 2006 to March 2011

Table 4. Correlation between each pollutant and cardiovascular mortality (first row) and its p-value (second row)

For each pollutant the correlation with mortality of cardiovascular diseases was calculated for men and women separately. Their correlation value and levels of significance are listed in Table 4. The only significant correlation was observed between ozone and mortality rate of cardiovascular disease in women (r= 0.31). Cardiovascular disease mortality rate increases as pollution with ozone rises. But in crude and adjusted negative binomial regression for temperature, humidity, and other air pollutants, increase in none of these pollutants was in relation with increase in cardiovascular mortality (Table 5).

Table 5. Crude and adjusted negative binomial regression analysis for the effect of each unit increase in pollutants on cardiovascular mortality in Kerman

4. Discussion

In the current study which was conducted based on 6-year data in the city of Kerman, there was no strong significant relation between the existence of air pollutants and cardiovascular mortality. Several epidemiological studies have been conducted regarding the relationship between air pollutants and cardiovascular mortality, including a project which assessed 20 major cities in Europe. The results showed that cardiovascular mortality rate increases 0.68% with each 10 µg/m3 increase in dusts (PM10) [14]. In another study which assessed 29 cities in Europe, results showed that with each 10 µg/m3 increase in dust (PM10), the overall mortality rate due to cardiovascular diseases rose 0.69 percent [15].

In a review article studying 15 cities in Italy during 1996 to 2000; it was observed that with increase in NO2, CO, SO2, and PM10, the overall cardiovascular mortality increased [16]. In other studies conducted in Birmingham, England [17] and Ohio State, U.S. [18], it was observed that with each 100 µg/m3 increase in dusts, the overall cardiovascular mortality rate rose with a relative risk of 1.06.

In a study conducted in Spain, a significant relation was observed between the number of cardiovascular cases and the concentration of SO2, soot, and CO with relative risks of 1.05, 1.038, and 1.029, respectively[19].

In a study conducted in Sydney Australia, the rate of emergency cardiovascular visits in patients over 65 years old were assessed over a 5-years period and a positive significant relationship was observed between emergency cardiovascular patient visits and dusts, CO, and NO2 [20].

In addition to environmental pollutants, climatic factors such as temperature, humidity, and pressure are effective on the incidence of cardiovascular diseases and this issue was considered in several studies [19] and in some of these studies, the relationship of these factors with mortality were calculated [3]. In this study, adjustment was done for temperature and humidity but this didn’t affect the results’ significance.

There are limited studies regarding this issue in Iran. In a study conducted by Mohammadi in Tehran, amongst air pollutants only NO2 had a significant relationship with cardiovascular mortality with a correlation coefficient of 0.64. In this study, climatic factors such as humidity, the minimum of temperature, and relative humidity had a significant relationship with cardiovascular and respiratory mortality [21]. In another study conducted by Gholizadeh in Tehran, there was a significant relation between CO and cardiovascular and respiratory mortality [22].

5. Conclusion

According to this study there was no relationship between the concentrations of O3, SO2, NO2, PM10, CO, and NO and cardiovascular mortality rate in the city of Kerman during 2006 to 2011. In order to assess the effect of pollutants on cardiovascular mortality, more studies are needed in cities with higher levels of air pollution. However, studying the epidemiology and the mechanisms of air pollution related health effects (including cardiovascular toxicity) will possibly identify specific causal agents that can be better regulated and increase the effectiveness of our efforts to reduce the risk of developing air pollution related health problems.

Acknowledgments

This proposal was approved by Environmental Medical Research Committee at the School of Public Health was funded by the Deputy of Research at Kerman University of Medical Science.

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