Air pollutants are any substance in the air that adversely affects the environment, health, and the national economy [1, 2]. Air pollution is a dangerous factor that directly targets people's health, raising the risk of respiratory infections, lung cancer, and heart disease. Exposure to air pollutants can cause many diseases for people in the long term or short term. The danger of air pollutants such as carbon monoxide (CO) is striking for patients, especially those with lung cancer or heart disease [3]. In the United States (US), the high prevalence of Asthma is attributed to the adverse effects of hazardous air pollutants (HAPs) [4]. Air pollution is an invisible killer that hides among people and threatens both youngsters and elderlies. Nine out of ten individuals worldwide suffer from air pollutants that deeply penetrate the lung tissue and the cardiovascular system. Hence, air pollution, with a mortality rate of 7 million people annually, contributes to 43% of lung cancer and 24% of strokes [5]. Two prominent air pollutants that pose a serious threat to ecosystems around the world are nitrogen dioxide (NO2) and sulfur dioxide (SO2) [6]. However, only a small number of research have looked at the geographical hotspots of NO2 and SO2, their developments, manufacturing, and sources in Asia.
There must be solutions found for the problem of pollution because it is a worldwide issue. Population growth, urbanization, industrialization, motorization, and modernization have all accelerated the rate of air pollution and taken it beyond a point at which it can be repaired on its own [7]. It is known that the effects of air pollution and associated synergistic interactions have an impact on a variety of resources, namely life forms, biodiversity, national treasures, and properties, as well as human health and life. As reported by the World Health Organization (WHO), CO, O3 on the earth's surface, sulfur oxides, nitrogen oxides, and Lead (Pb) are the six principal air pollutants that harm human health as well as the ecosystem [8]. Nitrogen dioxide (NO2), sulfur dioxide (SO2), and CO are significant ambient air pollutants. Exposure to NO2 with high intensity mainly causes catastrophic human injury [9]. Many factors contribute to the elevation of air pollution, like the pollutants emitted from municipal solid waste (MSW) in China [10] and air pollutant distance decay gradients around an upstream oil and natural gas (ONG) facility in South Los Angeles [11]. In Iran, using fossil fuels in refineries and factories has a striking impact on air pollution by generating gases and harmful chemicals. Due to the dangers of air pollution and its factors, the study to reduce the risk of air pollution is of great importance.
Risk assessment is an organized and systematic method to estimate risk for making decisions in challenging times. Accordingly, the factors must be examined, and the accident-prone and dangerous items must be specified in the organization. Risk assessment can be made with various methods that can be qualitative to quantitative [12]. Thus, many studies, as well as the current one, have focused on the issue of risk assessment and obtained many essential results [13–15]. In 2020, Masseran and Safari considered the intensity–duration–frequency (IDF) method for highlighting the relationship between the pollution intensity, duration, and return period [16]. In another study, Bai et al. selected Jilin Province in Northeastern China as a case study for air pollution evaluation [17]. The authors used principal component analysis (PCA) and noncarcinogenic risk model calculations to reach conclusions. Regarding the obtained results, the temporal distribution of pollutants in winter was much higher than in the other seasons. Coal-fired and automobile emissions were introduced as the primary sources of air pollution, with 62.37% and 19.15%, respectively. In 2019, Tian et al. used a detailed pollution analysis and dust dispersion model to evaluate the inhaled amount of road dust [18]. The results revealed that inhalation of fine dust adversely affects health due to dust loading. In the cutting-edge paper of 2020, the air quality index (AQI), aggregate AQI (AAQI), and health-risk-based AQI (HAQI) were evaluated as the criteria for specifying the health risks and characterizing the proportion of people suffering from air pollution. The AirQ2.2.3 model was employed to quantify the pollutants' health effects. PM10, caused by frequent dust storms, was the main contributor to air pollution in spring and winter. Besides, anthropogenic activities create PM2.5 pollution due to the coal-fired heating in winter. Xiong et al. defined six metrics for air pollution, including PM2.5, PM10, SO2, NO2, CO, and O3 in Sichuan [19]. The authors attempted to assess the health risk of the various age groups created through ambient air pollutants and obtained acceptable results. In a significant advance of 2022 [20], Lei et al. indicated that PM2.5, PM10, NO2, SO2, CO, and O3 concentrations reduced by 10.9%, 13.2%, 9.3%, 10.1%, 9.4%, and 5.5% from 2019 to 2020 in China. The findings emphasized the crucial role of O3 in assessing air quality and health risk.
In short, the literature pertaining to human health risks [21] strongly states that by interacting with the immune system, ambient NO2 exposure may raise the risk of respiratory tract infections [22]. Both healthy individuals and those with underlying lung diseases experience respiratory symptoms that SO2 exacerbates. Griffiths et al. [23] aim to advance the knowledge of the nature, makeup, and potential health effects of emissions from big incident fires to aid in the risk assessment procedure. Portable Fourier Transform Infrared (FTIR) monitoring performed as part of the UK's Air Quality in Major Incidents service provided real-world monitoring data. In 2023, Honscha et al. exploited the principles of human health risk assessment to see the adverse impacts of As, Cd, Se, Pb, Ni, NO2, and SO2 [24]. The obtained results proved that the emissions of such elements are not hazardous in Brazil. Air quality modeling is a valuable tool to forecast future air quality and choose emission reduction measures. The AERMOD dispersion model was used in another work to investigate the pollutant emission values resulting from the flares of the Maroon gas refinery, which is situated in the Iranian city of Ahvaz's suburb [25]. More studies are also summarized in Table 1 based on the method, risk assessment criteria, and case study location.
Table 1
A summary of the previous studies regarding the risk assessment of air pollution
No. | References / Year | Aim | Method | Location |
1 | [26] / 2019 | Examining the relationship between fine particulate matter (PM2.5) and meteorological variables and approximating the annual mortality from diseases caused by air pollution like chronic obstructive pulmonary disease (COPD) and lung cancer | Correlation analysis based on the WHO AirQ + software | Tehran, Iran |
2 | [27] / 2018 | Evaluation of human health risk considering the mortality rate caused by multiple air pollutants in transport corridors | Air contamination (Ri-MAP) model in a bid | National Capital Territory (NCT) of Delhi, India |
3 | [28] / 2020 | Specifying the inter-correlation among dominant air pollution index (API) for PM10 percentile values. The main pollutants’ clusters were specified using ambient monitoring data. | Machine learning (ML) algorithms | Malaysia |
4 | [29] / 2021 | Investigating the existing scientific information regarding the levels of air pollutants associated with the activities of chemical/petrochemical complex | A systematic review | Tarragona County |
5 | [30] / 2021 | Minimizing the adverse effects of air pollutants to protect plants | Analytical and scientific research | Any urban location |
6 | [31] / 2021 | Examining the temporal variations and spatial distributions of SO2, NO2, O3, CO, PM2.5 and PM10) | Considering thresholds exert excess risk (total) | China |
7 | [32] / 2022 | Specifying the relationship between pneumonia, weather, and environmental air pollutants | Spearman correlation and negative binomial regression modeling | Lampang Province, the Northern region of Thailand |
8 | [33] / 2022 | Examining exposure and inhaled doses to air pollutants for the children | WRF-Urban/GEOS-Chem/CMAQ models | Southeast Brazil |
Despite the remarkable interest due to the studies reviewed in Table 1, no study has assessed the risk of NO2, SO2, and CO emitted from the refinery of Phase 12 of South Pars. Gases that are delivered to flares in refinery plants are one of the most significant industrial wastes. Flares are tall chimneys where gas burns. They come in two varieties—open and closed—and three pressure ranges—low, middle, and high. The refinery business benefits from gas flares in three ways: reducing system shocks and fixing the refinery 3. the burning toxic gases. According to the Globe Bank, the globe burned almost 150 billion meters cubed of natural gas in 2008, adding 400 million tons of greenhouse gas to the atmosphere yearly. According to the data supplied, the top gas-burning nations are Nigeria, Russia, Iran, Algeria, Mexico, Venezuela, Indonesia, and the United States, in that order. Iran comes in first in the Middle East and third worldwide in terms of obtaining and utilizing renewable gas. Due to the importance of such issues [34], the current study simulates the status of air pollution in Kangan using CALPUFF software. The study's major innovation lies in the heart of accurate analytical outcomes and health risk assessment. More details regarding the method and location are provided in the second section. Then, the obtained results are examined and discussed in the third section. Finally, the findings and suggestions for future studies are given in the fourth section.