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Health Impacts of Exposure to PM10 on Inhabitants of Shiraz, Iran


1 Shiraz University of Medical Sciences, Shiraz, IR Iran
2 Department of Environmental Health, School of Health, Shiraz University of Medical Sciences, Shiraz, IR Iran
3 Department of Environmental Health, School of Health, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran
4 Department of Epidemiology, School of Health, Shiraz University of Medical Sciences, Shiraz, IR Iran
*Corresponding author: Abooalfazl Azhdarpoor, Department of Environmental Health, School of Health, Shiraz University of Medical Sciences, Shiraz, IR Iran. Tel: +98-7137251001, Fax: +98-7137260225, E-mail: [email protected].
Health Scope. 2015 November; 4(4): e31015 , DOI: 10.17795/jhealthscope-31015
Article Type: Research Article; Received: Jun 24, 2015; Revised: Jul 19, 2015; Accepted: Aug 2, 2015; epub: Nov 25, 2015; ppub: Nov 1, 2015

Abstract


Background: Particulate matters have harmful effects on human health and can intensify mortality and disease.

Objectives: The purpose of this study was to evaluate the health impacts of particulate matter < 10 μ in diameter (PM10) on the inhabitants of Shiraz, one of the largest cities in southern Iran with a population of 1,500,000.

Materials and Methods: The AirQ2.2.3 model developed by the world health organization European centre for environment and health was used in this study. Excess cases of mortality, total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for cardiovascular disease (CVD) were calculated.

Results: The results of this study show that 25.3% cases of total mortality, 1.1% cases of cardiovascular mortality, 0.3% cases of respiratory mortality, and 3.3% cases of hospital admissions for CVD in 2012 occurred at particulate matter concentrations > 40 µg/m³. About 15.9% cases of total mortality, 0.7% cases of cardiovascular mortality, 0.2% cases of respiratory mortality, and 2% cases of hospital admissions for CVD in 2013 occurred at particulate matter concentrations >20 µg/m³. Moreover, in 2012, > 85% of the studied health effects were related to days with a PM10 concentration of < 400 µg/m³, and in 2013, about 99% of the studied health effects were related to days with a PM10 concentration of < 189 - 180 µg/m³.

Conclusions: According to the results obtained, the largest numbers of deaths and illnesses were due to the high average PM10 concentration or an increase in the number of days of exposure to this pollutant.

Keywords: Relative Risk; Incidence; Mortality

1. Background


Since the 1970s and 1980s, the increased rates of mortality and illness have been attributed to air pollution incidents (1-3). Air pollution is a nonuniform mixture of particulate matter, nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone. It has been established in many epidemiological studies that air pollution, especially with particulate matter <10 μ in diameter (PM10), has a serious effect on human health (4-6). The effects of air pollution include increased rates of hospital admissions, cardiovascular diseases (CVDs), asthma attacks, mortality, and reduced life expectancy (7-11). The major sources of particulate matter include road traffic, human intervention, fixed sources of combustion, transportation, power plants, thermal plants, and industrial processes (12). Short- and long-term contact with PM10 can lead to lung irritation, immune system reactions, lung contraction, dyspnea, damaged cells, increased coughing, asthma, hospital admissions, chronic bronchitis, cancer, and death (7-11).


In recent years, several studies have shown a relationship between short- and long-term exposure to particulate matter in the air and various health effects (13-15). A study by the world health organization (WHO) showed that an increase of 10 µg/m³ in particulate matter can lead to an increase of 1 - 3% in the mortality rate (16). Jeong reported the relationship between PM10 and total mortality, cardiovascular and respiratory mortality, and hospital admissions for CVD and respiratory diseases (17). Similarly, Naddafi et al. (18) studied the relationship between PM10 and total mortality, cardiovascular and respiratory mortality, and hospital admissions for CVD and respiratory diseases. Fattore et al. (19) showed a relationship between PM10 and total mortality, cardiovascular mortality, and respiratory mortality. Goudarzi et al. (20) described the relationship between daily mortality and PM10 in Tehran. Zallaghi et al. (21) showed a relationship between daily mortality and PM10 in Ahvaz, Kermanshah, and Bushehr. According to the results obtained by Zallaghi et al. in Ahvaz, 1.8% of the cases of respiratory mortality and 2.5% of the cases of deaths were attributable to PM10 concentrations >20 μg/m3 (22).


In the recent decades, the metropolitan city of Shiraz, located in southwestern Iran, with an area of 1,268 km2 and a population of 1,500,000, has experienced an increase in air pollution, especially with PM10 owing to dust storms. This air pollution problem in Shiraz is exacerbated by topographic and climatic factors, sunlight, and intermittent temperature inversion (23).


The AirQ model or the Air Quality Health Impact Assessment software (AirQ 2.2.3) developed by the WHO is a reliable and useful tool for estimating the potential health effects of human exposure to certain pollutants in an urban area during a specific time period (24).

2. Objectives


The purpose of this study was to evaluate the short-term health effects of the PM10 pollutant on the inhabitants of Shiraz in 2012 and 2013. The rates of relative risk (RR) and baseline incidence (BI) were calculated and localized using local statistics. This is rarely seen in similar studies.

3. Materials and Methods


3.1. Place of Study

This study was conducted in Shiraz, the center of Fars Province in southwestern Iran and one of the 7 metropolises in Iran with a population of > 1,500,000, an area of 1,268 km2, and an altitude of 1,540 meters above sea level, which is located at latitude 29/37 and longitude 52/32. The rates of total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for CVD were measured on a daily basis, and the PM10 concentrations in 2012 and 2013 were used as the base values.


3.2. Environmental and Health Information

Information on PM10 concentrations was collected on a daily basis from 2 air pollution monitoring stations in Setad square and Darwaze Kazeroon affiliated with Shiraz EPA. The daily average values for temperature and humidity were obtained from the Shiraz Meteorological Organization. Statistics on total mortality, cardiovascular mortality, and respiratory mortality were collected on a daily basis from the municipality of Shiraz. Data on the daily rates of hospital admissions for CVD were obtained from the Shiraz central emergency department in 2012 and 2013.


3.3. Statistical Methods

The potential health effects of human exposure to air pollutants were measured using the AirQ 2.2.3 developed by the WHO European centre for environment and health. Assessment using this software is based on attributable proportion (AP) that represents the health impacts of exposure of a particular population to air pollutants and shows the relationship between exposure and health outcomes without confounding effects on this relationship. AP is calculated using the following formula (19, 25):


(1)

Where AP is the attributable proportion of health outcomes and RR (c) is the relative risk of health outcomes in the group c of exposure. The RR of selective health outcomes can be obtained using the exposure-response functions. P(c) is the proportion of the target population in group c of exposure. Considering the baseline incidence of the selected health outcomes, the amount attributable to the population exposure can be calculated as follows:


(2)

Where, IE is the incidence of health outcomes in the exposed subjects, and I is the baseline incidence of health outcomes in the population under study. Finally, considering the population size, the number of excess cases can be calculated as follows:


(3)

Where NE is the number of cases attributable to exposure, and N is the size of the population under study.


The RR (per 10 µg/m³ increase in the daily average PM10 concentration) for total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for CVD was calculated using a generalized additive model. The BI for total mortality, cardiovascular mortality, and respiratory mortality during the study period was obtained from the registration office of Shiraz. The BI of hospital admissions for CVD and respiratory diseases was obtained from the central emergency department of Shiraz.


3.4. Exposure Assessment

The required parameters for the software (annual and seasonal maximum and annual 98 percentile) were obtained for the PM10 pollutant, and the pollutant concentrations were reported in terms of 10 µg/m³ as a 24-h average. Then, the number of exposures was estimated in the 1,500,000 population of Shiraz.

4. Results


Table 1 shows the average concentrations of PM10 in a year, in summer and winter as well as the maximum values in summer and winter. As shown in this table, the average PM10 concentrations in 2012 and 2013 were 111.95 and 70.6 µg/m³, respectively. A decrease in the average concentration of the pollutant was observed in 2013 as compared to that in 2012. The results indicate that the average PM10 concentrations in 2012 and 2013 were 2.24 and 1.41 times the basic standard concentrations of PM10 published by the National Ambient Air Quality Standards (NAAQSs) and were 5.60 and 3.53 times the standard concentrations of PM10 specified by the WHO. As shown in Table 1, the maximum PM10 concentration in Shiraz in 2012 and 2013 was observed in summer. The maximum PM10 concentration in 2012 was 960.88 µg/m³ and was observed in summer, while in 2013, it was 192.49 µg/m³.


Table 1.
Summary of Data on the PM10 Concentrations in Shiraz in 2012 and 2013

Figure 1 shows the percentage of exposure of Shiraz inhabitants to different concentrations of PM10 in 2012 and 2013. As shown in the chart, the highest number of days of exposure to PM10 in 2012 and 2013 were in the 80 - 89 and 60 - 69 µg/m³ concentration ranges, which was higher than the NAAQSs for the annual average PM10 concentration.


Figure 1.
Percentage of Exposure of Shiraz Inhabitants to Different Concentrations of PM10

Figure 2 shows the cumulative rates of total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for CVD on the basis of a lower, central, and upper RR in the specified concentration intervals (10 µg/m³) in 2012 and 2013. Table 2 shows the RR and BI values estimated with 95% confidence interval (CI) per 10 µg/m³ increase in the daily average PM10 concentration associated with total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for CVD.


Figure 2.
Cumulative Rates of Total Mortality, Cardiovascular Mortality, Respiratory Mortality, and Hospital Admissions for CVD According to Exposure to PM10 at Concentration Intervals

Table 2.
BI and RR With a 95% CI Per 10 µg/m³ Increase in the Average Daily PM10 Concentration

Table 3 shows the short-term health effects of exposure to PM10 on total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for CVD according to the RR and BI shown in Table 2 for the 10 µg/m³ reference level. As shown in this table, the number of cases of total mortality and respiratory mortality attributed to PM10 at a low and middle RR index (RR = 1) equals zero. Therefore, the attributable proportion and number of excess cases for this pollutant is zero. In Table 3, the number of total excess deaths associated with PM10 based on the upper RR was about 379 in 2012 and about 293 in 2013, indicating a decrease in the total mortality in 2013 as compared to that in 2012. Moreover, as shown in this table, the rates of cardiovascular mortality, respiratory mortality, and hospital admissions for CVD decreased in 2013.


Table 3.
Attributable Proportion and Number of Excess Cases for PM10 by Health Effects in 2012 and 2013

5. Discussion


This study investigated the effects of short-term exposure to PM10 pollutants on total mortality, cardiovascular mortality, respiratory mortality, and hospital admissions for CVD in 2012 and 2013 by using the AirQ model.


As shown in Table 3, the number of total mortality cases attributed to PM10 in 2012, based on the upper RR and BI of 454.3, was about 379 per 100,000 people. The results show that the number of excess cases of total mortality attributable to PM10 decreased by 22.6% in 2013 compared to that in 2012. Moreover, in 2012, the number of cases of cardiovascular mortality, respiratory mortality, and hospital admissions for CVD attributable to PM10, based on the upper RR and BI values in Table 2, was 16, 4, and 49, respectively. As shown in Table 3, the rates of cardiovascular mortality, respiratory mortality, and hospital admissions for CVD decreased by 37.8%, 38.3%, and 38%, respectively, in 2013, compared to those in 2012. According to the cumulative values presented in Figure 2, in 2012, 25.3% cases of total mortality, 1.1% cases of cardiovascular mortality, 0.3% cases of respiratory mortality, and 3.3% cases of hospital admissions for CVD were attributable to PM10 concentrations of > 40 µg/m³. In 2013, 15.9% cases of total mortality, 0.7% cases of cardiovascular mortality, 0.2% cases of respiratory mortality, and 2% cases of hospital admissions for CVD were attributable to PM10 concentrations of >20 µg/m³. Moreover, the cumulative values show that the largest number of deaths due to exposure to PM10 was 55 at a concentration of >400 µg/m³ in 2012 in Shiraz and was 53 at a concentration of 60–69 µg/m³ in 2013. More than 85% of the health effects studied in 2012 occurred on the days when the PM10 concentration was <400 µg/m³. In 2013, about 99% of the health effects occurred on the days when the PM10 concentration was < 180 - 189 µg/m³.


In a similar study, Zallaghi et al. (21) studied the health effects of PM10 in Kermanshah and Bushehr using the AirQ model. The results showed that in Kermanshah, 12% of the CVD cases and 17% of the respiratory disease cases were attributable to PM10 concentrations of > 30 µg/m³, and in Bushehr, 14% of the CVD cases and 19% of the respiratory disease cases were attributable to PM10 concentrations of > 20 µg/m³. In a related study by Goudarzi et al. in Tehran, 4% of the respiratory mortality cases were associated with PM10 concentrations of > 20 µg/m³ (20). In the present study, the number of health effects was relatively lower because of the lower PM10 concentration in Shiraz city. A 1-year study on 1-month-old children in North America showed that a 20 µg/m³ increase in the daily mean PM10 concentration led to an 82% increase in the risk of death (26). Tominz et al. (27) studied the health effects of PM10 by using the AirQ model and showed that 1.8% of the cases of total mortality and 2.5% of the cases of respiratory mortality were attributable to PM10 concentrations > 20 µg/m³. In this study, the PM10 concentration was higher in Shiraz than in Trieste City. In a study by Guo et al. (28), there was an approximate 0.23% increase in hospital admissions per 10 µg/m³ increase in the PM10 concentration, and in a study by Chen et al. in North China in 2010, there was a 0.036% increase in hospital admissions per 10 µg/m³ increase in the PM10 concentration (29). In a study by Shakour et al. in Egypt, there was a 4% increase in hospital admissions for respiratory diseases per 10 µg/m³ increase in the PM10 concentrations (30). The results of the present study differ from those of the previous studies because of the differing geographic, demographic, and climatic characteristics. The health effects of PM10 in Shiraz were consistent with those reported by other similar studies, and a comparison of the results of this study and other studies conducted in Iran and worldwide shows that the largest number of deaths and illnesses occurred owing to the high average PM10 concentration or an increase in the number of days of exposure to this pollutant.


In this study, the health effects of PM10 on the inhabitants of Shiraz were quantified using RR and BI values obtained from local statistics. Previously, such an assessment was performed by the WHO by using default BI and RR values. Considering the varying geographic and climatic features in different countries, further studies with RR and BI values calculated according to local statistics and characteristics are needed.

Acknowledgments

The authors would like to thank the Shiraz university of medical sciences for providing financial support to this project. The authors would also like to thank the staff of the environmental protection agency, central emergency department, and meteorology office in Shiraz for their cooperation in this project.

Footnotes

Funding/Support: This study is the result of a project (7016) entitled “A survey of respiratory and cardiovascular disease, death, accidents rate related to air pollution (2012-2013 years) in Shiraz city by AirQ2.2.3 software.” This project was financially supported by the Shiraz University of Medical Sciences.
Authors’ Contributions: Abooalfazl Azhdarpoor was involved in the development of the study design and protocol, data analysis and interpretation, and manuscript drafting and is a guarantor. Aezam Mohammadi, Abbas Shahsavani, and Hamidreza Tabatabaee contributed to the development of the study protocol, data analysis and interpretation, and manuscript drafting.

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Table 1.

Summary of Data on the PM10 Concentrations in Shiraz in 2012 and 2013

Parameter 2012 2013
Annual mean, μg/m 3 111.95 70.60
Summer mean, μg/m 3 133.76 82.24
Winter mean, μg/m 3 78.73 58.38
Summer max, μg/m 3 960.88 192.49
Winter max, μg/m 3 273.10 136.46
98 percentile, μg/m 3 489.47 151.97

Table 2.

BI and RR With a 95% CI Per 10 µg/m³ Increase in the Average Daily PM10 Concentration

Health Endpoint Baseline Incidence a Relative Risk
Total mortality 454.3 1 (1 - 1.006)
Cardiovascular mortality 125.3 1.0007 (1.0005 - 1.0009)
Respiratory mortality 32.3 1 (1 - 1.001)
Hospital admission for cardiovascular disease 373.6 1.0006 (1.0003 - 1.0009)
a Crude rate per 100,000 inhabitants.

Table 3.

Attributable Proportion and Number of Excess Cases for PM10 by Health Effects in 2012 and 2013

Health Endpoint 2012 2013
Attributable Proportion No. of Excess Cases Attributable Proportion No. of Excess Cases
Total mortality 0.0 (0.0 - 5.5591) 0.0 (0.0 - 378.8) 0.0 (0.0 - 3.5083) 0.0 (0.0 - 293.1)
Cardiovascular mortality 0.6820 (0.4881 - 0.8752) 12.8 (9.2 - 16.4) 0.4224 (0.3021 - 0.5424) 7.9 (5.7 - 10.2)
Respiratory mortality 0.0 (0.0 - 0.9715) 0.0 (0.0 - 4.7) 0.0 (0.0 - 0.6023) 0.0 (0.0 - 2.9)
HA for cardiovascular disease a 0.5852 (0.2935 - 0.8752) 32.8 (16.4 - 49.1) 0.3623 (0.1815 - 0.5424) 20.3 (10.2 - 30.4)
a Hospital Admission.

Figure 1.

Percentage of Exposure of Shiraz Inhabitants to Different Concentrations of PM10

Figure 2.

Cumulative Rates of Total Mortality, Cardiovascular Mortality, Respiratory Mortality, and Hospital Admissions for CVD According to Exposure to PM10 at Concentration Intervals

(1)

(2)

(3)