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Center for Air Resources Engineering and Science, Clarkson University, Potsdam, USADepartment of Public Health Sciences, University of Rochester School of Medicine and Dentistry, Rochester, USA
Air pollution is an emerging risk factor for human health like cancer and other health outcomes in developing countries, especially in Iran where air pollutants concentrations are high. However, the data on health effects of air pollution are limited.
Objective
In this study, we have estimated the mortality for all causes (TM) and for cardiovascular diseases (CM), as well as the number of hospital admissions due to cardiovascular (HA-CVD) and respiratory diseases (HA-RD), chronic obstructive pulmonary diseases (HA-COPD), and acute myocardial infarction (AMI) due to exposure to common air pollutants.
Materials and Methods
In our study, the World Health Organization (WHO) method was applied to assess the mortality and morbidity rates from published relative risk (RR) and baseline incidence (BI) values.
Results
The results showed that 4.60% (95% CI: 3.50–5.31%) TM, 4.96% (95% CI: 3.16–10.50%) CM, 4.97% (95% CI: 3.04–6.81%) HA-RD, 5.55% (95% CI: 3.77–7.82%) HA-CVD, 2.50% (95% CI: 0–4.61%) HA-COPD and 4.73% (95% CI: 1.14–4.65%) AMI, respectively can be attributed to daily PM10 and SO2 concentrations exceeding 10 μg/m3.
Conclusion
To reduce the adverse health impact of air pollution, health advices and recommendations by local health authorities should be given to general population especially for vulnerable people i.e. children, elderly or people with chronic lung and cardiac pathologies during the dusty days.
Particulate matter (PM) is considered as one of the most harmful airborne pollutant emitted from biogenic and anthropogenic sources or formed from atmospheric reactions. In recent years, west Asia was influenced by desert dust storms, increasing the number of dusty days as well as the daily average of PM with an aerodynamic diameter less than 10 μm (PM10).
Metals and pathogenic microorganisms can be transported by desert dust at downwind sites. Sulfur dioxide (SO2) is a toxic gas with a pungent and irritating smell. It is released naturally by volcanic activity and also produced as a by-product of combustion of sulfur containing fuel.
Inhalation of SO2 is mainly related to respiratory and pulmonary diseases, difficulty in breathing, reduced visibility, chronic obstructive pulmonary diseases (COPD) and premature death.
Epidemiological studies showed that high levels of PM10 in the air can lead to cardiovascular diseases such as myocardial infarction, stroke, heart failure and venous thromboembolism.
Khaniabadi et al showed that an increase in SO2 concentration by 10 μg/m3 increases AMI morbidity by 2.7% and HA-COPD by 2%. In Cyprus, Middleton et al found that hospital visits due to cardiovascular diseases increased after dust episodes. The aim of this study was to assess the mortality and morbidity due to exposure to PM10 and SO2 in Hamadan (Iran).
2. Material and methods
2.1 The study area
The study area was Hamadan, the headquarters of Hamadan province, located in western Iran accounting 548,000 inhabitants (Fig. 1). The dry season occurs between June and September with the wet season extending into October, like Mediterranean climates. The most important emission source of air pollutant is dust storms events coming from the desert areas of West Asia.
In our study, Air Quality Health Impact Assessment (AirQ2.2.3) software proposed by the World Health organization (WHO) was used to assess the mortality and morbidity in the study area. Morbidity indices assessed were total and cardiovascular mortality, hospitalizations due to cardiovascular diseases, respiratory diseases, chronic obstructive pulmonary diseases, and acute myocardial infarction.
AirQ is a specialized tool that enables the user to assess the potential impact of air pollution exposure of a certain air pollutant on health of human in a defined area during a certain period of monitoring.
Attributable proportion defined as the fraction of health consequences in a public exposed to a specific air pollutant. The attributable proportion (AP) can be easily calculated by the following equation.
(1)
Where, AP is the attributable proportion of the health impact, RR is the relative risk for a certain health impact in category "c" of exposure taken from several epidemiological studies, and P(c) is the population proportion in category "c" of exposure.
The number of each case per population unit can be estimated when the baseline frequency of the specific health impact in the population was known as follows:
(2)
where IE is the number of cases attributable to air pollution per every population unit and I is the population unit. Knowing the size of population, the number of excess cases associated with the exposure can be calculated using Eq. (3):
(3)
where N and NE are the size of population under study and the number of excess cases, respectively.
In our study, PM10 and SO2 concentrations after processing and coding mortality and morbidity as health impacts and exposed population data were imputed into the software AirQ2.2.3 for the period 2015. Furthermore, the number of excess cases of total mortality (TM), cardiovascular mortality (CM), hospitalizations for cardiovascular diseases (HA-CVD), respiratory diseases (HA-RD) and chronic obstructive pulmonary diseases, and acute myocardial infarction (AMI) in exposed inhabitants were estimated by relative risk (RR) and baseline incidence (BI) defauted by the WHO for estimation of mortality and morbidity.
2.3 Sampling
The monitoring station was located at Hamadan Environmental Protection Agency (HEPA), which was responsible for maintenance and operation. The hourly PM10 and SO2 concentrations were continuously measured for one-year in 2015 then used to calculate the daily mean concentrations.
2.4 Relative risk and baseline incidence
In AirQ model, the main parameters related to health effect are relative risk (RR) and baseline incidence (BI). The RR is the probability of developing a disease due to exposure to a single pollutant.
The values of RR and BI (per 100,000 individuals) are attributed to different types of mortality and morbidity cases and were published by the WHO from epidemiological studies (Table 1). The required data to run AirQ include daily and annual averages, winter and summer averages, annual 98 percentile and the population. Low, high and median RR values (i.e. 95% confidence interval) were considered in this health risk assessment.
Table 1Baseline incidence (BI) and relative risk (RR) for this study with 95% confidence interval.
Table 2 illustrates the mean annual, summer and winter of PM10 and SO2 concentrations. According to the National Ambient Air Quality Standards (NAAQS) guide, the daily average of air quality for PM10 and SO2 are 150 and 20 μg/m3, respectively. The annual average concentrations of PM10 and SO2 were 78.0 and 45.1 μg/m3, respectively. The summer PM10 (87.0 μg/m3) was higher than those of winter (69.0 μg/m3); while for SO2, the winter average (48.7 μg/m3) was more than summer average (41.2 μg/m3).
Table 2The summer, winter and annual concentrations of PM10 and SO2 of Hamadan in 2015.
Total (TM) and cardiovascular mortality (CM), daily hospitalizations due to respiratory (HA-RD) and cardiovascular diseases (HA-CVD) during Middle Eastern Dust (MED) storms, attributable to daily PM10 and SO2 levels, are presented in Table 3. The number of excess cases of total and cardiovascular mortalities as result of exposure to PM10 and SO2 were 51 and 22 persons, respectively. The HA-RD and HA-CVD attributed to PM10 were 336 and 133 persons, respectively. Also, SO2 led to hospital admissions of 30 and 22 persons for COPD and Acute MI, respectively.
Table 3Estimated attributable proportion (AP) percentage and number of excess cases in one year owing to short-term exposure above 10 μg/m3 for PM10 and SO2.
Fig. 2 shows the results of AirQ model quantification of the health risk due to exposure to PM10 and SO2 in Hamadan (Iran). These figures exhibit the cumulative number of excess cases versus PM10 and SO2 concentration intervals. The cumulative number of TM, CM, HA-RD and HA-CVD due to exposure to PM10 within median RR were 253, 134, 336 and 131 persons, respectively, while TM, CM, HA-COPD and AMI due to SO2 exposure were estimated to 51, 22, 30, 22 persons (Fig. 2).
Fig. 2Mortality and morbidity due to exposure to PM10 (from dust storms) and SO2.
The results also showed that about 4.60% (95% CI: 3.50–5.31%) TM, 4.96% (95% CI: 3.16–10.50%) CM, 4.97% (95% CI: 3.04–6.81%) HA-RD, 5.55% (95% CI: 3.77–7.82%) HA-CVD, 2.50% (95% CI: 0–4.61%) HA-COPD and 4.73% (95% CI: 1.14–4.65%) AMI can be directly linked to PM10 and SO2 concentrations greater than 10 μg/m3. For each 10 μg/m3 increase in the PM10 concentration, the risk of TM and CM increased by 0.74% and 0.80%, respectively. While for SO2, the total and cardiovascular mortality increased by 0.48% and 1.2%, respectively. Additionally, the risk of hospitalizations for RD and CVD increased by 0.80% and 0.90%, respectively with increase in PM10 levels by of 10 μg/m3. Hospitalizations for COPD and Acute MI increased by 0.44% and 1.0%, respectively with increase of 10 μg/m3 in SO2 levels.
4. Discussion
In this study, AirQ model proposed by the WHO were used to investigate the mortality and morbidity due to increased PM10 and SO2 concentrations among the people. The impacts of PM10 and SO2 on increased total and cardiovascular mortality, and hospital admissions due to respiratory and cardiovascular diseases, COPD and acute myocardial infarction were estimated. The mean annual, summer and winter PM10 concentrations were lower than the levels reported by
in Kermanshah (Iran). The 63-day study of Marzouni et al for the PM10 level was higher than the NAAQS criteria (150 μg/m3). A related study in Suwon (Korea) reported similar annual PM10 average of 52 μg/m3, which is 1.04 times higher than NAAQS criteria.
were higher than those determined in this study. That higher level of PM10 observed during summer might probably resulted from higher temperature and wind speed that favors atmospheric turbulent and resuspension of windblown dusts. The maximum person/day exposure in Makkah (Saudi Arabia) was determined in the range of 200–249 μg/m3 of PM10 concentrations.
In Italy, the maximum percentage of the days in which people in Mazzano were exposed to different PM10 levels was found to be in the range of 40–49 μg/m3,
similar to level interval measured in the our study for PM10, but 30–39 μg/m3 for SO2. The annual mean of SO2 of 45.1 μg/m3 measured in this study was higher than the NAAQS permissible level of 20 μg/m3. In winter, the level of SO2 (48.7 μg/m3) was higher than the value measured in summer (41.2 μg/m3), indicating intensive combustion of fossil fuels for heat generation at winter period.
Two time-series studies in Hong-Kong and London showed there is no evidence of a threshold for health impacts of 24-h average SO2 levels in morbidity for cardiac diseases.
In the American Cancer Society study, a significant association between SO2 and mortality was documented between 1928–1998, in which the lowest mean SO2 concentration measured was 18 μg/m3, while the highest average value was 85 μg/m3.
A similar study between 1991 and 2010 indicated that PM was responsible for most of the number of excess cases of respiratory death in New-Delhi in India.
In this study, the number of excess cases of HA-RD and HA-CVD due to exposure to PM10 were 336 and 133 persons in 2015 as well as 253 premature deaths with an annual PM10 mean concentration of 78 μg/m3. The results of our study indicated that 96.8% of the health impacts including TM, CM, HA-CVD and HA-RD occurred when PM10 concentration was higher than 20 μg/m3 and 97% of mortality and morbidity were attributed to PM10 concentrations above 200 μg/m3.
Khaniabadi et al reported that 188 premature deaths were estimated by AirQ model during 2014–2015 in Kermanshah due to exposure to PM10.
The TM and CM in Khorramabad (Iran) calculated by Nourmoradi et al were 235 and 136 persons in 2015. The research work also showed that MED events have an important effect on air quality as result of increase in PM10 concentration. In Ahvaz (Iran), 74% of the health endpoints occurred in days with SO2 levels lower than 100 μg/m3
A significant correlation between PM10 levels and HA-RD was reported in both studies of Chen et al and Guo et al in Anshan and Beijing (China), respectively. The studies revealed more health impacts in the cold season than the warm season. The results of a cohort study in 25 cities of China indicated that 1.8% (0.8–2.9%) and 1.7% (0.3–3.2%) increase of mortality risk was relevant to 10 μg/m3 increase in PM10 for cardiovascular and respiratory mortalities.
Another investigation was conducted by Park et al to find out the impact of Asian Dust Storm (ADS) on the hospital admissions due to the asthma and COPD. The PM10 levels during ADS episode reached 146.6 μg/m3 while in normal days, the values is around 60 μg/m3. The hospitalizations significantly increased on the days with ADS for asthma (RR = 1.21; 95% CI: 1.01–1.19) and COPD (RR = 1.29; 95% CI: 1.05–1.59).
In Suwon of South Korea, the number of excess cases of respiratory death attributed to exposure to air pollutants was calculated as 16.8 persons for PM10 and 2 persons for SO2, respectively.
According to the study of Jeong in Suwon, the number of excess cases for the HA-RD and the HA-CVD were 462 and 179, respectively. The study reported higher values of HA-CVD and HA-RD for PM10 in comparison with the present study.
A large-scale study in Europe (Aphea-II study) showed that each 10 μg/m3 increase in SO2 was significantly correlated with 0.7% rise in all HA-CVD within two days.
A similar study in six Italian cities showed that the increase in the daily mean average of SO2 by 10 μg/m3 was associated with 2.8% of increase in diseases.
In Estonia, the number of excess cases of HA-RD and HA-CVD due to exposure to PM10 were 71 (95% CI 43–104) and 204 persons (95% CI 131–260) respectively in Tallinn in 2006 with an annual average concentration of PM10 of 32.2 μg/m3.
In United States, Fairley demonstrated that between 1980 and 1986, each 10 μg/m3 increase in PM10 level up to 150 μg/m3 resulted to 0.12% increase in the risk rate of mortality among inhabitants of San Jose. Shumway et al showed that for PM10 lower than 100 μg/m3, increase in PM10 level by 10 μg/m3 caused 1.1% increase in risk of mortality in Los Angeles. In Detroit, a study of health effects showed that an increase in daily SO2 level by 10 μg/m3 was linked to a rise in 2% risk of mortality.
The role of particulate size and chemistry in the association between summer time ambient air pollution and hospitalization for cardiorespiratory diseases.
The assessment of effect of air pollution on human health is an important topic because air pollution continues to be a risk factor, especially in Iran where air pollutant concentrations continue to rise. Local analyses of the health effects of air pollution are limited, thus the use of AirQ model is necessary to provide estimates of the potential health outcomes. Our study also has limitations:
In quantitative assessment of health impacts of air pollution, the interactions between different contaminants are not evaluated and this information is not available. In the approach used here, the health impacts are focused on single pollutant without considering the simultaneous exposure to the multiple pollutants to which the public is actually exposed. Another limitation is the RR estimates that were derived in studies of different populations in comparison to that under investigation. A further limitation is potential exposure misclassification. This approach assumes that concentrations measured at the central monitoring point are representative of the exposure of all people living in a city.
5. Conclusion
AirQ model proposed by the WHO had been adopted to investigate the mortality and morbidity due to increased common air pollutants concentrations.
Since the geographic, demographic and climate characteristics are different and not well evaluated, further studies are recommended for quantification of other health impacts and assessment the health impacts of exposure to other air pollutants in urban areas. Although the findings from this study agreed with other reported studies around the world, there is still need to acquire more data on specific relative risk and baseline incidence values according to climate, geographical, and statistical features. To fully protect human health from the adverse effects of air pollution, studies are needed of the long-term health impacts of these pollutants in developing countries like Iran.
To diminish the harmful effects, public education, application of technical methods for decreasing sulfur emissions from different sources such as oil and petrochemical industries, reduction diesel and fossil fuels consumption, and careful monitoring of air pollution will have an important role as strategies control. To reduce the adverse health impact of air pollution, health advices by local health authorities should be given to general population, especially the vulnerable persons with chronic lung and heart pathologies, the elderly and children. Furthermore, preventive risk mitigation measures at governmental scale should be taken for the control of dust entering to the country such as spreading mulch, washing streets, management of water bodies, and planting some new species of plants to intercept airborne dust. Other actions should focus on eco-friendly transport systems, formidable measures necessary to reduce the high traffic density and proper management traffic systems that will reduce the negative impacts of air pollution.
Acknowledgments
The authors wish to thanks to the Ahvaz Jundishapur University of Medical Sciences for supporting of this study (ETRC-9636).
References
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Association of particulate matter impact on prevalence of chronic obstructive pulmonary disease in Ahvaz, southwest Iran during 2009–2013.
The role of particulate size and chemistry in the association between summer time ambient air pollution and hospitalization for cardiorespiratory diseases.
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