Reconstruction of exposure to methylene diphenyl-4,4'-diisocyanate (MDI) aerosol using computational fluid dynamics, physiologically based toxicokinetics and statistical modeling.

OBJECTIVES: This study employed computational fluid dynamics (CFD), physiologically based toxicokinetics (PBTK), and statistical modeling to reconstruct exposure to methylene diphenyl-4,4'-diisocyanate (MDI) aerosol. By utilizing a validated CFD model, human respiratory deposition of MDI aerosol in different workload conditions was investigated, while a PBTK model was calibrated using experimental rat data. Biomonitoring data and Markov Chain Monte Carlo (MCMC) simulation were utilized for exposure assessment. RESULTS: Deposition fraction of MDI in the respiratory tract at the light, moderate, and heavy activity were 0.038, 0.079, and 0.153, respectively. Converged MCMC results as the posterior means and prior values were obtained for several PBTK model parameters. In our study, we calibrated a rat model to investigate the transport, absorption, and elimination of 4,4'-MDI via inhalation exposure. The calibration process successfully captured experimental data in the lungs, liver, blood, and kidneys, allowing for a reasonable representation of MDI distribution within the rat model. Our calibrated model also represents MDI dynamics in the bloodstream, facilitating the assessment of bioavailability. For human exposure, we validated the model for recent and long-term MDI exposure using data from relevant studies. CONCLUSION: Our computational models provide reasonable insights into MDI exposure, contributing to informed risk assessment and the development of effective exposure reduction strategies.

Health impact and related cost of ambient air pollution in Tehran.

Ambient air pollution represents one of the biggest environmental risks to health. In this study, we estimated the avoidable mortality burden attributable to ambient air pollution in Tehran, and derived the economic impact associated with these health effects. Using PM2.5 data from ground-level air pollution measurements in Tehran, we estimated PM2.5 exposure for 349 neighborhoods in Tehran, by the Environmental Benefits Mapping and Analysis Program (BenMAP-CE). We considered five scenarios related to PM2.5 levels: an increase to 35 µg/m3; a reduction to 25 µg/m3; a reduction to 15 µg/m3; a reduction to 10 µg/m3 (the WHO's air quality guideline value); and a full roll-back, assuming a reduction to 2.4 µg/m3. All scenarios used 2017 p.m.2.5 levels as a starting point. Using the concentration response function of the Global Exposure Mortality Model (GEMM), we estimated a total of 7146 (95% CI: 6596-7513) adult (age ≥25 years) deaths attributable to PM2.5 in 2017. The leading causes of death were ischemic heart disease (3437; 95% CI: 3315-3516), stroke (886; 95% CI: 693-1002), lower respiratory infections (531: 95% CI: 414-589), chronic obstructive pulmonary disease (364; 95% CI: 271-420), and lung cancer (274; 95% CI: 236-298). The estimated total annual economic benefit (2017) of reducing PM2.5 concentration levels to 2.4 µg/m3 was USD 0.591 (95% CI: 0.447-0.624) billion per year, using the value of a life year (VOLY) approach, and USD 2.894 (95% CI: 2.671-3.043) billion per year, using the value of a statistical life (VSL) approach.

Source Apportionment of Total Suspended Particles (TSP) by Positive Matrix Factorization (PMF) and Chemical Mass Balance (CMB) Modeling in Ahvaz, Iran.

There is a compelling need for apportionment of pollutants' sources to facilitate their reduction through proper management plans. The present study was designed to determine the contribution of each possible source of total suspended particles in Ahvaz's ambient air using positive matrix factorization (PMF), chemical mass balance (CMB), and the SPECIATE database. The sampling program undertaken followed EPA's guidelines and finally resulted in 74 samples. The concentration of 33 elemental and 10 ionic species were measured during a whole year. Three modeling approaches were applied: PMF, the integrated use of PMF and CMB, and the integrated use of the SPECIATE database and CMB. Six sources were derived by PMF: crustal dust (30.6%), industrial and mining activities (25.4%), motor vehicles (23.4%), marine aerosols (11.5%), secondary inorganic aerosols (5.7%), and road dust (3.4%). The contributions of sources from PMF-CMB approach were crustal dust (32.9%), industrial and mining activities (20.9%), motor vehicles (19.7%), marine aerosols (11.1%), secondary inorganic aerosols (9.2%), and road dust (9.36%). Seven sources were derived by SPECIATE-CMB approach: crustal dust (23.2%), industrial and mining activities (20.1%), motor vehicles (17.5%), marine aerosols (12.4%), secondary inorganic aerosols (4.8%), road dust (5.3%), and "nondetermined sources" factor (16.7%). Despite the different contributions of sources, there is a noticeable consistency between the results of these approaches. Furthermore, because of the approved performance of combined receptor models in previous studies and the presence of sufficient data on the number of species and samples, the results of the PMF-CMB approach are possibly the most realistic among those of the three applied approaches.

Temporal variations, regional contribution, and cluster analyses of ozone and NOx in a middle eastern megacity during summertime over 2017-2019.

Particulate matter is usually regarded as the dominant pollutant in Tehran megacity in Iran. However, the number of ozone exceedance days significantly increased in recent years. This study analyzes simultaneous measurements of O3 and NOx (NO+NO2) concentrations to improve our understanding of ozone evolution during the summers of 2017 to 2019. The k-means clustering technique was used to select five representative air quality monitoring sites in Tehran to capture O3 and NOx concentrations' variability. The findings show that all of the investigated sites failed to meet the ozone non-attainment criterion. The ozone weekend effect is seen in the study of weekday/weekend differences in 2017 and 2018, but not in 2019, which can be due to the shift in the ozone production regime. The summer mean variation analysis can also be used to deduce this regime change. In 2017, the O3 and NO2 summer mean variations suggest a holdback in the NO2 upward trend and a reversal in the O3 downward trend that had been in place since 2012. Air mass back trajectory clustering reveals that east and north-east air mass clusters have the most significant impact on Tehran's O3 pollution and the highest regional contribution to OX. The study of OX against NOx shows that the regional contribution to OX increased from 2017 to 2018 and then decreased in 2019; however, the local contribution is the opposite. The diurnal analysis of the regional and local contributions to OX indicated that OX in Tehran might be primarily affected by pollutants from a short distance. The findings reveal critical changes in the behavior of O3 in recent years, indicating that decision-makers in Tehran should reconsider air pollution control measures.

Meteorological dependence, source identification, and carcinogenic risk assessment of PM2.5-bound Polycyclic Aromatic Hydrocarbons (PAHs) in high-traffic roadside, urban background, and remote suburban area.

The Polycyclic Aromatic Hydrocarbons (PAHs) bound to ambient fine Particular Matter (PM2.5) are currently drawing a lot of attention due to their adverse health effects increasing lung cancer risk in humans. In this study, The PM2.5 samples were collected by high volume air samplers simultaneously from three different sites (high-traffic roadside, urban background, and remote suburban) in Tehran, Iran during warm and cold seasons (from July 2018 to March 2019), and 16 PAHs were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). Unlike previous studies, a remote suburban area was chosen so as to observe the spatial differentiation in PM2.5-bound PAH characteristics. In high-traffic roadside site, the average concentration of total PM2.5-bound PAHs (Æ©PAHs) was 3.7 times the concentration value in remote suburban area. Average (Æ©PAHs) ranged from 5.54 ng/m3 for remote suburban area to 20.67 ng/m3 for high-traffic roadside site. In all sites, seasonal trends of PAH concentrations elucidated high concentrations in the cold season and low concentrations in the warm season. Correlation analysis between Æ©PAHs and atmospheric factors (meteorology parameters and criteria air pollutants) indicated the heterogeneous processes play an important role in the level of PAHs. The results of diagnostic ratio (DR) analysis disclosed that the dominant source of PM2.5-bound PAHs was the combustion of liquid fossil fuels. Despite the fact that incremental lifetime cancer risk (ILCR) via inhaling PM2.5-bound PAHs varied significantly in high-traffic roadside site and remote suburban site, its value was beyond the acceptable risk level in both sites. Our results suggested that effective regulations are needed to monitor PAHs concentrations and reduce PAHs emissions from liquid fossil fuel combustion so as to mitigate the potential carcinogenic risk of PAHs in ambient air. Supplementary Information: The online version contains supplementary material available at 10.1007/s40201-022-00821-2.

CFD simulation for dispersion of benzene at a petroleum refinery in diverse atmospheric conditions.

Atmospheric parameters play a vital role in the dispersion of air pollutants. Benzene is a confirmed human carcinogen. It is also a neurotoxin and an irritant compound. The objective of this study was to examine the CFD simulation by Fluent16 software to simulate and analyze the effect of atmospheric conditions on the dispersion of benzene in eight different scenarios in a petroleum refinery. According to the results of this study, the highest and lowest impacts of atmospheric parameters occurred on spring days and autumn nights, respectively. Wind direction did not have a significant effect on the benzene distribution due to the artificial ceiling of piping installations in the computational domain. However, the wind speed had a critical role in the benzene dispersion. The maximum concentration occurred at 36- to 37-m distance from the inlet boundary for all scenarios except winter nights. On winter nights, this distance increased to 38 m. Benzene concentrations were the highest at their sources of release. They decreased after the artificial ceiling of the pipelines was at 5.5- to 7-m height where the air displacement was not sufficient, and therefore, leading to a gradual reduction in concentration. The accumulation of benzene concentration in the small domain was noticeable compared to the benzene concentration distributed in the total computational domain, and the authors recommended control measures in this domain. This study demonstrated CFD simulation methodology could enable the investigators to predict the benzene concentration dispersion in the atmosphere of a petroleum refinery plant. These findings can be used by occupational health engineers for health risk assessment of refinery personnel involved with maintenance operations and engineering control systems.

Risk assessment of occupational exposure to benzene using numerical simulation in a complex geometry of a reforming unit of petroleum refinery.

There has been an increasing concern about the continuous and the sudden release of volatile organic pollutants from petroleum refineries and occupational and environmental exposures. Benzene is one of the most prevalent volatile compounds, and it has been addressed by many authors for its potential toxicity in occupational and environmental settings. Due to the complexities of sampling and analysis of benzene in routine and accidental situations, a reliable estimation of the benzene concentration in the outdoor setting of refinery using a computational fluid dynamics (CFD) could be instrumental for risk assessment of occupational exposure. In the present work, a computational fluid dynamic model was applied for exposure risk assessment with consideration of benzene being released continuously from a reforming unit of a refinery. For simulation of benzene dispersion, GAMBIT, FLUENT, and CFD post software are used as preprocessing, processing, and post-processing, respectively. Computational fluid dynamic validation was carried out by comparing the computed data with the experimental measurements. Eventually, chronic daily intake and lifetime cancer risk for routine operations through the two seasons of a year are estimated through the simulation model. Root mean square errors are 0.19 and 0.17 for wind speed and concentration, respectively. Lifetime risk assessments of workers are 0.4-3.8 and 0.0096-0.25 per 1000 workers in stable and unstable atmospheric conditions, respectively. Exposure risk is unacceptable for the head of shift work, chief engineer, and general workers in 141 days (38.77%) in a year. The results of this study show that computational fluid dynamics is a useful tool for modeling of benzene exposure in a complex geometry and can be used to estimate lifetime risks of occupation groups in a refinery setting.

Dust storm simulation over Iran using HYSPLIT.

Particulate matters have detrimental effects on human health, environment and economic. This pollutant may emit from anthropogenic or natural sources. On global scale, main proportion of natural particulate matter release to the atmosphere because of wind erosion from arid and semi-arid regions. Recently, the amount of dust coming from Arabian countries has dramatically increased, especially dust storms that are affecting western and even central parts of Iran. This phenomenon has caused a lot of environmental problems. Dust source identification and trajectory simulation using numerical techniques are the main aims of this study. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model dust module and trajectory simulation are utilized in this research and two case studies are investigated (in May and June 2010). The base of the HYSPLIT dust module is the PM10 dust storm emission algorithm for desert land use. This methodology is applied to estimate hotspots and trajectories. Due to the results, dust storms started on May 17th and June 7th because of high wind shear (>8.5 m/s) from the western Syrian Desert. The source region limited to 32.50 °N to 33.80 °N and 38.00 °E to 38.80 °E coordinates. Dust plumes lifted and dispersed towards the east and southeast of the sources and reached Ahvaz on May 18th and June 8th. The average of PM10 concentration in these dates reached 625 and 494 µgm3 on Ahvaz monitoring stations, respectively. Moreover, the results gained from the model for dust motion simulation are similar to the MODIS satellite images.

Environmental air pollution and acute cerebrovascular complications: an ecologic study in tehran, iran.

BACKGROUND: In this study, we aimed to assess the association between air pollution and cerebrovascular complications in Tehran, one of the most air-polluted cities in the world, among different subgroups of patients with stroke in 2004. METHODS: In this ecologic study, we calculated the daily average levels of different air pollutants including CO, NO(X), SO(2), O(3), and PM(10) and also humidity and temperature on the day of stroke and 48 hours prior to stroke in 1 491 patients admitted with the diagnosis of stroke in eight referral hospitals in different areas of Tehran. Then, we evaluated the association between the rate of stroke admissions and the level of the selected pollutants, humidity, and temperature on the day of stroke and 48 hours prior to stroke among different subgroups of patients. RESULTS: There was no significant association between the same-day level of the pollutants and the rate of stroke admissions, but an association was seen for their level 48 hours before stroke. These associations differed among different subgroups of age, sex, history of underlying diseases, and type of stroke. Same-day temperature had a reverse association in patients with hemorrhagic stroke and in patients without a history of heart disease or previous stroke. A direct significant association was seen for humidity level 48 hours before stroke in patients with a history of heart disease. CONCLUSIONS: It is inferred that air pollution has a direct association with the incidence of stroke and these association differs among different subgroups of patients. The results of this study are not time-dependant and can be generalized to different times and regions. Moreover, these results may be useful for environmental health policy makers.