Estimate of cardiovascular and respiratory mortality related to Sulfur dioxide pollutant in Ahvaz

 
Introduction
Sulfur dioxide has been widely studied among the human- made pollutants. Air pollution is a major environmental risk to health. The less air pollution, the better the cardiovascular and respiratory health of the population will be, both long- and short-term. several studies have demonstrated relation between on short and long term effects exposure to air pollutants with human health. The  exposure  to sulfur  dioxide  is  extremely risky  for  people  health  because  these compounds enter the circulatory system directly through  the  airways. Sulfur dioxide can be absorbed into your body through your nose and lungs. The most important effects of sulfur dioxide air  pollution include: increase rates hospital admissions, asthma attacks, cardiopulmonary disease, death and number of the years of life lost. Sulfur dioxide can be dangerous to the respiratory system and the functions of the lungs and can also lead to irritation of eyes. Ahvaz as the center of east khouzestan province in southwest of Iran is a one of the most populated and polluted cities. Ahvaz city, with a population of 1 million approximately, with an area of 8152 square kilometers,  the capital city of Khuzestan Province is located between 48 degree to 49°29′ east of Greenwich meridian and between 31 degrees and 45 minutes to the north of the equator. Ahvaz is located in an arid area in south west of Iran with long and hot summertime. Temperature reaches to 50 degree of centigrade on June and July. Keep in mind, high density of industries (steel, oil and gas) makes Ahvaz as one of most important emitter. With the rapid economic growth in Ahvaz, the level of air pollution from both motor vehicles and industrial emissions has drastically increased. Furthermore, health effect of air pollution in terms of Sulfur dioxide, ozone and particulate matter in most of megacities particularly Ahvaz was reported. This research aims to estimate the health effects (total of death, cardiovascular and respiratory mortality) related to Sulfur dioxide pollutant in 2011.
 
 
Figure. 1 The study area location and sampling station in Khuzestan Province (Ahvaz), south west of Iran
 
Materials and methods
In this retrospective study, was used to assess the potential effects of Sulfur dioxide exposure on human health in Ahvaz city (located in south-western Iran) during year 2011.The concentration of Sulfur dioxide pollutant was measured in 2011 in four stations in Ahvaz. The most important part of analysis is data processing that encompasses modification of temperature and pressure, primary processing (the deletion, spreadsheet and synchronization), secondary processing (writing code and condition correction), formulation and filtering. Finally, Estimate of health effects related to Sulfur dioxide pollutant in the cur of Ahvaz. We calculated health effects related to Sulfur dioxide by AirQ_2.2.3 based on the utilizing relative risk, attributable proportion and baseline incidence from WHO data. This model includes four screen inputs (Supplier, AQ data, Location, Parameter) and two output screens (Table and Graph). For estimated of health impact attributable to the exposure of air pollution on the target population using AirQ model, that estimate the this impacts to specific air pollutants on a resident population in a certain area and period.
 
Results and discussion
The primary and secondary standard of sulfur dioxide according to national ambient air quality standard (NAAQS) 24-hour is 150 µg/m³. Table 1 shows that annual mean of sulfur dioxide in Ahvaz was 157/5 µg/m³ in 2011 which is higher than WHO air quality guidelines and also much higher than NAAQS values. In view of sulfur dioxide concentrations, Mohitzist and Havashenasi were the highest and the lowest stations during this year. The yearly average, summer mean, winter mean and 98 percentile of sulfur dioxide concentrations in these stations has presented in table 1.
 
Table 1. Highest and lowest concentrations of Sulfur dioxide(μg/m³) corresponding to stations
 




Stations
 
                            Parameter


 Average Ahvaz


lowest stations
(Havashenasi)


highest stations
 (Mohitzist)




Annual mean


157/5


69/63


212/26




Summer mean


53/12


27/54


82/32




Winter mean


172/32


89/44


267/1




98 percentile


192/71


105/21


295/47




 
Sum of total numbers of death attributed to Sulfur dioxide was 194 cases and number of cardiovascular of death in centerline relative risk was 156 cases that 67 percent of them happened when the Sulfur dioxide concentration was less than 90 μg/m³. Relative risk and estimated Attributable Proportion percentage for total numbers of death, cardiovascular of death, respiratory mortality and myocardial infarction were calculated in table 2. Baseline incidence (BI) for this health effect for Sulfur dioxide were 1013, 497, 66, 132 and per 10⁵ so total numbers of death were calculate 194 (RR=1.0040 and AP=1. 7265%), the number of cardiovascular mortality were calculate 156 (RR=1.0080 and AP=3. 3216%), the number of Respiratory mortality were calculate 25 (RR=1.010 and AP=4. 0236%) and the number of myocardial infarction were calculate 33 (RR=1.0064 and AP=2. 8652%) at centerline of relative risk.
 
Table 2- Estimated relative risk indicators and the component attributable to Sulfur dioxide cases attributable to total numbers of death, cardiovascular of death, respiratory mortality and myocardial infarction




Health effects attributable to Sulfur dioxide


RR (relative risk)


Estimated AP (%)


Estimated number of  excess cases (persons)




total numbers of death


1.004


1.7265


194




cardiovascular death


1.008


3.3216


156




Respiratory death


1.01


4.0326


25




myocardial infarction


1.0064


2.8652


33




 
Also, based on the results of this study, we found that in Ahvaz number of respiratory mortality attributed to Sulfur dioxide were 25 cases and number of myocardial infarction in centerline relative risk was 33 cases that 46 percent of them happened when the Sulfur dioxide concentration was less than 60 μg/m³ in Ahvaz city during 2011. In this study, we estimate total numbers of death, cardiovascular of death, respiratory mortality and myocardial infarction were associated with short and long term fluctuations in concentrations of Sulfur dioxide pollutant in people, using AirQ model in Ahvaz, Iran. In similar work Gudarzi et al In 2009 estimate the Sulfur dioxide hygienic effects in Tehran (capital of Iran). Based on their results, almost 7.82 and 3.6 percent of all cases of whole Respiratory deaths and Hospital Admissions Respiratory Disease are attributed to Sulfur dioxide. In another study Mohamadi et al In 2009 calculated  health effects air pollutants in Ahvaz. Based on their results, approximately 4.03 percent of total Respiratory deaths and 1.8 percent Hospital Admissions Respiratory Diseaserelated to Sulfur dioxide. Zalaghi et al In 2010 Survey of health effects of air pollution Ahvaz, Bushehr and Kermanshah. Based on their results, approximately 4.4 percent in Ahvaz, 8.64 percent in Kermanshah and 3.33 percent of total Respiratory deaths attributed to Sulfur dioxide.
 
 
Conclusion
According to the present research findings and the relieving effects of potential total numbers of death, cardiovascular of death, respiratory mortality and myocardial infarction of Sulfur dioxide exposure on human health in Ahvaz city (located in south-western Iran) during year 2011. Results show that approximately Ahvaz with 5 percent is one of the most polluted cities. The analysis of statistics and comparison of mean and maximum concentration of Sulfur dioxide in four stations in Ahvaz during 24 hrs with air pollution index show that the higher percentage of deaths perhaps could be the result of higher average Sulfur dioxide or because of sustained high concentration days in Ahvaz.