Iranian Journal of

Background and Objective: In the recent decade, critical condition of particulate matters (PMs) concentration is considered as one of the most important issues in Tehran megacity. Due to sparse spatial distribution of air quality monitoring stations and economic considerations, researchers proposed remote sensing technique as a fast and economical way to obtain complete spatial and temporal coverage of PM concentrations.
Materials and Methods: In this study, aerosol optical depth (AOD) retrieved by MODIS along with meteorological parameters were used to develop statistical linear mixed effect (LME) model and estimating ground-level PM_2.5 concentrations. AOD data with a spatial resolution of 3 km from 13 monitoring stations and  meteorological data from 5 synoptic stations were extracted over Tehran during 2013.
Results: The results showed that the proposed model was able to explain about 57%-72% of daily PM_2.5 concentration variations. Temporal analysis of predicted PM_2.5 concentrations could follow the curve trend which was obtained from the observed PM_2.5 measurements with a reasonable level of accuracy. Best performance of the model was in May 2013 during a model-fitting and cross-validation practice. Also, the spatial distribution of the estimated PM_2.5 concentrations was consistent with the measured values in the monitoring stations.
Conclusion: Based on the spatial distribution map of the estimated PM_2.5, central and northern parts of Tehran were the most polluted areas in the study region. The result showed that the LME model using the satellite-derived AOD and meteorological variables could provide an accurate prediction of ground-level PM_2.5 concentrations.
 

Background and Objective: The adverse health effects of polycyclic aromatic hydrocarbons (PAHs) have received significant attention in recent years. This study aimed to measure the concentration of PAHs associated with fine particles and assess the health risks posed by these compounds.
Materials and Methods: A total of 38 air samples were collected from the central part of Isfahan city using a particle sampler equipped with an inlet to capture particles smaller than 2.5 µm (PM_2.5). The samples were analyzed using GC-MS, and molecular ratios were used to identify potential sources of PAHs. Additionally, a Monte Carlo simulation was employed to perform a probabilistic risk assessment of carcinogenic and non-carcinogenic effects of PAHs for two groups:  children and adults.
Results: Out of the 16 priority PAH compounds, seven compounds were identified, with average concentrations ranging from 0.003 to 17.8 ng/m³. Molecular ratios indicated that pyrogenic sources were the main contributors to PAHs in the air. The median carcinogenic risk for children and adults was estimated to be 3.1×10^-8 and 5.99×10^-8, respectively. The median non-carcinogenic risk for PAH compounds was estimated at 3.08×10^-1.
Conclusion: The probabilistic risk assessment revealed that the PAHs concentrations associated with fine particles do not pose a significant risk to exposed individuals. However, it is important to note that this study focused solely on the risk assessment of PAHs associated with fine particles. A comprehensive risk assessment of all PAHs present in the atmosphere is, therefore, recommended.
 

Background and Objective: The present study was designed to investigate the spatial and temporal (hourly, daily, monthly, and seasonal) variations in ambient fine particulate matter (PM_2.5) concentrations in Tehran from 21 March, 2023, to 19 March, 2024, and estimate the number of premature deaths attributable to PM_2.5.
Materials and Methods: Hourly PM_2.5 data were obtained from 41 air quality monitoring stations across Tehran. Subsequently, 29 validated stations were identified for assessing spatial changes in pollutant concentrations and estimating the associated health effects. The latest version of the AirQ+ software (version 2.2.4) was employed to estimate health impacts attributable to PM_2.5. Additionally, updated baseline data and the population of Tehran were used to assess the health effects of air pollution.
Results: The annual average concentration of ambient PM_2.5 in Tehran over the study period was approximately 32 µg/m³ for the entire city. At validated monitoring stations and across neighborhoods, the concentrations ranged from 20.8–47.5 µg/m³ and 22.2–46.3 µg/m³, respectively. These levels were approximately 4 to 9 times higher than the World Health Organization's (WHO) annual air quality guidelines and 2 to 4 times higher than the NAAQS. The number of deaths attributable to long-term exposure to ambient PM_2.5 in adults aged 30 and above in Tehran during the study period was estimated to be 9,321 (95% confidence interval: 7,232–10,313) for concentrations exceeding 5 µg/m³.
Conclusion: The results of this study highlight that ambient PM_2.5 concentrations in Tehran over the study period consistently exceeded the WHO air quality guideline and the NAAQS. Furthermore, a comparison of pollutant concentrations across all validated monitoring stations and neighborhoods reveals that residents in all parts of Tehran experienced poor air quality. However, concentrations were significantly higher in some areas, particularly the central and southern parts of the city, compared to the northern regions.