Investigation of air pollution and health effects as per dose-response functions and prioritizing responsibility of pollutants based on Multi-Criteria Decision Making computations: A case study

With the growth of industrialization and urbanization in megacities, some emerging disasters occur such as air pollution mortality, increasing cancer risks, decreasing life expectancy, descending prosperity, and Human Development Indexes (HDI). In addition, with the raising population of cities, the quantity and quality of air pollutions are increased based on vehicle application rate, industrial activities, agricultural efforts and etc. In this research, with the application of Dose-Response Functions in air pollution, some parameters such as chronic disease-based mortality, life expectancy reduction based on chronic and acute effects, and ozone gas health risks are computed in a case study of Mashhad city, Iran. The outcomes have illustrated the life expectancy is reduced in a case study around 8.22 and 8.51 years for men and women, respectively. Plus, the results of statistical health scrutinizing have demonstrated that the mortality of chronic effects based on air pollution emissions is calculated around 20 percentages in the case study. Likewise, with the application of two different methods in Multi-Criteria Decision Making (MCDM) containing Analytic Hierarchy Process (AHP) and ELimination Et Choice Translating Reality (ELECTRE) the responsibility of each pollution is determined. As per the mentioned computations, Particle Matter 2.5 (PM2.5) has the most role in increasing the health risk of air pollution in Mashhad City, Iran.


Introduction
Nowadays air pollution is one of the adverse aspects of industrialization and technological advances in cities which is indeed intensifi ed by the growing demand for manufacturing processes in the last several decades [1]. The occurrence of air pollution in densely populated urban areas has been associated with tragic events in the second half of the 20th century in the United States and Europe. The results of time studies in the early 1990s in different parts of the world have shown that even in areas with a low concentration of pollution, the attributed load of diseases to air pollution is very high due to the large coverage of at-risk population and the sensitivity of certain groups of society [2]. high concentration resulted in 60 death [3]. 2. London incident in 1952 caused by temperature inversion and accumulation of pollutants which led to 4000 death [4]. 3

. Smog phenomena
in 2008, Ontario which led to 9500 premature death a year [5]. 4. accumulation of pollutants in 2014 Delhi, caused by a high PM 2.5 concentration which led to 10500 at-risk premature death [6]. Also, in 2005, an air pollution risk survey in Tehran showed that 1600 people were experiencing severe coughs and other tough signs of illnesses [7]. Such calamities indicate that there is a direct relation between air pollution and casualties [8]  was measured by using the regression method and the results showed that PM 2.5 is the most responsible pollutant for this reduction [13]. Also, in 2015 a survey using fi eld measurement and remote sensing was conducted to assess the amount of decrease in life expectancy and the responsible pollutant in India [14]. Later on, World Health Organization (WHO) analyzed the most 13 polluted cities in India focusing on PM 2.5 which pointed out that the most reduction of life expectancy is in Delhi with the highest concentration of PM 2.5 . Also in 2015 WHO reported the average amount of PM 2.5 in the most polluted cities of India, China, Europe, and America which were 46, 40.4, 21.7, and 9.6 μg/m 3 respectively [14]. In 2017 an open cohort in the USA using a two-pollutant model of PM 2.5 and O 3 was conducted and measured the risk of death, associated with the increase of exposure to those pollutants, results showed that all-cause mortalities raised by 7.3% for PM 2.5 and 1.1% for O 3 [15]. In 2018 the impact of temperature inversion associated with air pollution on human health was explored in Hanoi, Vietnam by collecting data from monitoring centers in the region showing levels of NO 2 , SO 2 , PM 10, and PM 2.5 and came to the conclusion that acute respiratory and cardiovascular diseases were signifi cantly increased during inversion periods [16]. In 2019 the association of PM 2.5 and PM 10 with all-cause diseases among 652 cities in 24 countries was investigated and showed that on average an increase of PM 10 concentrations by 10 μg/m 3 in a 2-day average will result in a higher percentage of daily mortality of some diseases like all-cause, cardiovascular and respiratory by 0.44%, 0.36%, and 0.47% respectively, the same scenario occurred for PM 2.5 by 0.68%, 0.55% and 0.74% respectively [17]. Again in 2019, the effect of air pollution on human health was analyzed in China by comparing China Dynamic Survey to air pollution data which indicated that an increase in air pollution concentration considerably reduced citizen's health levels [18].

Materials and Methods
In the present study, via analytical methods such as dose-response functions, the impact of air pollution on both pathogens and human health has been investigated in a large city of Iran, Mashhad. The steps are described below.

Creating a database
There are 12 air pollution monitoring centers in Mashhad that monitor, measure, and index 5 kinds of pollutants including CO, NO 2 , O 3 , PM 2.5, and SO 2 ( Figure 2). since there are usually consequent fouls in monitoring equipment, one of the most important matters in collecting and analyzing the measured data is to implement expert methods and engineering judgment according to UNEP criteria [19] in order to modify them. In fact, engineering judgment means amending some data which are not logical. They could easily be recognized and corrected by the experts who are operating monitoring equipment. Hence, collected data were evaluated by brainstorming method twice and those that could not pass UNEP criteria were removed for the next phases.

Data processing using dose-response functions
Applied studies on dose-response functions provide results based on the concentration of air pollutants and human health. 4 factors are considered in this research, as follows.

Adult mortality (chronic diseases)
In a research in 2014, two different rates presented for the risk of PM 2.5 per 10 μg.m -3 which are 1.04 and 1.06 [20].
Regarding some recent studies [21,22], in the present study,

Dec reased life expectancy due to chronic diseases
Researches conducted by the EU on the evaluation of the life expectancy index due to chronic diseases are described in equations number 2 and 3 [23], which are the basis of calculations in the present research. .   .

Diseases caused by ozone emission
Surveys have shown that with each 10 μg.m -3 increase of ozone concentration in the air, the relative risk of adult mortality rises by 0.3% [25] also, hospital admission of chronic respiratory diseases (older than 65 years) will grow by 12.5 people per 100,000 [26]. The present research has analyzed some mortality parameters related to ozone emission including intense and quick contact, hospital admission of respiratory diseases, low limitation of daily activity, and using bronchodilators [27].

Prioritizing main pollutants
One of the important goals in monitoring and analyzing air pollution in large cities is determining main air pollutants as the dominant infl uential factor. This comparison in one year period has created a management perspective that can help to allocate the needed budget and time to treat air pollution. Therefore, according to Table 1

Results and discussions
All results according to utilizing dose-response functions in Mashhad are completely discussed below.

Adult mortality
As mentioned in the last sections some data collected in monitoring stations are amended because of and equipment errors based on expert's ideas this data for PM 2.5 is provided in Table 2 equation.1 tells that per 10 μg.m -3 increase in PM 2.5 concentration adult casualties rise by 5 percent. Statistical analysis shows that PM 2.5 concentration is the highest at Torogh station and the lowest at Mashin Abzar station averagely (annually) with the amount of 41.71 and 17.08 μg.m -3 respectively. Calculations show that adult mortality due to chronic diseases for Mashhad in comparison with cities without pollution rises by 20.85% at the maximum rate and by 8.54% at the minimum rate. Since the average concentration of PM 2.5 is 27.6 μg.m -3 it can be concluded that 13.8% of people in Mashhad on average are at risk of death due to chronic diseases.
In the last two decades, we have witnessed the expansion of the city and the growth of industries around Tehran; the capital city of Iran, according to the annual government report adult mortality due to chronic disease was calculated by 19.02% in 2011. Similarly, the average number of death due to chronic diseases reported in India and China is 20.2% and 23% respectively which means these two countries have a more critical situation than Iran cities. The mortality rate due to chronic diseases in Europe and the United States of America has also been reported by 10.85% and 4.8% respectively which represents a better condition. It should be noted that these calculations are based on an annual average which shows a higher risk and a more critical situation than longer periods. All of the above refers to chronic diseases.

The state of life expectancy according to chronic diseases
Based on the dose-response diagram slope which was previously noted in equations 2 and 3 life expectancy reduces by 6.7×10 -4 units of PM 2.5 and SO 2 concentration and reduces by 4×10 -4 units per each μg increase of NO 2 and PM 10 concentration.
Reported results of PM 10 concentration have not been confi rmed by authentication tests due to large errors in the measurement process. The minimum and maximum amount of PM 2.5 , NO 2, and SO 2 concentration and their infl uence on the reduction of life expectancy in 2014 have been described in Table 3.
Results show that the appearance of chronic diseases caused by the existing PM 2.5 , NO 2, and SO 2 in the environment decreases life expectancy by 11.39% at maximum and 3.49% at minimum rate.  [28]. Decreased life expectancy data due to chronic diseases in the present research has been compared to others in Table 4.

The state of diseases caused by ozone emission
Based on validated data in the pollutant monitoring center of Mashhad side effects of ozone emission are described in Table 5. Note that equ.6 is used to convert ozone concentration data into μg.m -3 since main data are given in ppb [30]. Surveys conducted in 2015 for 5 metropolitan cities in Iran show that Mashhad is the 2 nd large city in Iran with the most cumulative mortality with 148 people per day. This information together indicates that Mashhad is in a highly critical situation.

Prioritizing of pollutants in a year
To prioritize pollutants based on dangerous side effects AHP and ELECTERE methods have been used and results are shown in Table 6