Journal of Research in Environmental Health

Journal of Research in Environmental Health

Assessment of Air Pollution Control Strategies in the London Metropolitan Area and Their Potential for Local Adaptation to Mashhad

Document Type : Research article

Authors
Saeedeh Fouladi 1
Nayera Naimi 2
Maryam Sarkhosh 3
1 MSc in Environmental Health Engineering, Department of Environmental Health Engineering, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran.
2 Student Research Committee, Department of Environmental Health Engineering, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran.
3 Department of Environmental Health Engineering, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran.
10.22038/jreh.2026.98546.1761
Abstract
Background and Objective: Urban air pollution is currently recognized as one of the most important environmental and public health challenges worldwide and is responsible for millions of premature deaths annually. Following the historical Great Smog of 1952, London has implemented comprehensive and effective policies that have resulted in substantial improvements in air quality. Given the effectiveness of these policies and the shared challenge of air pollution in the metropolitan city of Mashhad, this study aimed to analyze London's experience and propose a practical, locally adapted framework for reducing air pollution in Mashhad.

Materials and Methods: This descriptive-analytical study used population data, concentrations of air pollutants, including NO₂, PM₁₀, PM₂.₅, and O₃, and transportation-related indicators for the period 1990–2022. Data were extracted from reliable sources, including the London Air Quality Network (LAQN), Transport for London (TfL), and the Greater London Authority (GLA). Pearson's correlation test was used to assess the relationships between population growth and pollutant concentrations.

Results: The population of London increased from 6.79 million in 1990 to 9.54 million in 2022. Despite population growth, the annual NO₂ concentration at the roadside station decreased from 95 µg/m³ in 1997 to 43 µg/m³ in 2021. At the same station, PM₁₀ concentration decreased from 50 µg/m³ in 1997 to 16 µg/m³ in 2021. PM₂.₅ concentration at the North Kensington station also decreased from approximately 20 µg/m³ in 2008 to 9 µg/m³ in 2021. The Pearson correlation test revealed a strong inverse correlation between population growth and the reduction in concentrations of NO₂, PM₁₀, and PM₂.₅. In contrast, a positive correlation was observed between population growth and increased O₃ concentrations. Controlling pollutants led to a 44% reduction in NO₂ concentrations in central London.

Conclusion: London's success in reducing air pollutant concentrations despite population growth has resulted from an integrated approach involving emission-based vehicle zoning, modernization of the transportation fleet, development of green infrastructure, and promotion of active transportation. Given the structural similarities between London and Mashhad, targeted adaptation of London's experience to Iran's specific conditions could represent an effective step toward reducing air pollution and improving public health in Mashhad.

Open Access Policy: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/
Keywords
Urban Air Pollution
Particulate Matter (PM₁₀ And PM₂.₅)
Nitrogen Dioxide(NO₂)
Exposure Assessment
Policy Localization
Ultra Low Emission Zone (ULEZ)
1. Alliance N. State of Global Air 2025: A report on air pollution and its role in the world's leading causes of death. Boston, MA: Health Effects Institute. 2025.
2. Murage P, Milner J, Fitch A, Macintyre HL, Vieno M, Maji KJ, et al. A novel approach using synthetic population models to assess how urban vegetation alters health inequalities in PM2. 5 exposure. Urban Forestry & Urban Greening. 2026:129665. https://doi.org/10.1016/j.ufug.2026.129665
3. Strobl K, Irfan SA, Masood H, Latif N, Kurmi O. Association between PM10 exposure and risk of myocardial infarction in adults: A systematic review and meta-analysis. PLoS One. 2024;19(5):e0301374. https://doi.org/10.1371/journal.pone.0301374 PMid:38691568 PMCid:PMC11062553
4. Orellano P, Reynoso J, Quaranta N, Bardach A, Ciapponi A. Short-term exposure to particulate matter (PM10 and PM2. 5), nitrogen dioxide (NO2), and ozone (O3) and all-cause and cause-specific mortality: Systematic review and meta-analysis. Environment international. 2020;142:105876. https://doi.org/10.1016/j.envint.2020.105876 PMid:32590284
5. Mansouri Daneshvar MR, Khatami R, Ebrahimi M. An analysis of urban heat island based on the temperature inversion across the atmospheric boundary layer in Mashhad, Iran (2018-2022). Spatial Information Research. 2024;32(5):607-22. https://doi.org/10.1007/s41324-024-00585-x
6. Kermani M, Farkhani EM, Joulaei F, Jafari AJ, Shahsavani A. A time-series analysis of the short-term effects of daily PM2. 5 exposure on cause-specific mortality in Mashhad, Iran (2019-2024). Scientific Reports. 2026. https://doi.org/10.1038/s41598-026-48267-y PMid:41965437 PMCid:PMC13230966
7. Hadei M, Hopke PK, Shahsavani A, Raeisi A, Jafari AJ, Yarahmadi M, et al. Effect of short-term exposure to air pollution on COVID-19 mortality and morbidity in Iranian cities. Journal of Environmental Health Science and Engineering. 2021;19(2):1807-16. https://doi.org/10.1007/s40201-021-00736-4 PMid:34729185 PMCid:PMC8553398
8. Naimi N, Sarkhosh M, Nabavi BF, Najafpoor A, Musa Farkhani E. Estimating the burden of diseases attributed to PM2. 5 using the AirQ+ software in Mashhad during 2016-2021. Scientific reports. 2024;14(1):24462. https://doi.org/10.1038/s41598-024-74328-1 PMid:39424839 PMCid:PMC11489694
9. Karimi B, Samadi S. Mortality and hospitalizations due to cardiovascular and respiratory diseases associated with air pollution in Iran: A systematic review and meta-analysis. Atmospheric environment. 2019;198:438-47. https://doi.org/10.1016/j.atmosenv.2018.10.063
10. Karimi B, Samadi S. Long-term exposure to air pollution on cardio-respiratory, and lung cancer mortality: a systematic review and meta-analysis. Journal of Environmental Health Science and Engineering. 2024;22(1):75-95. https://doi.org/10.1007/s40201-024-00900-6 PMid:38887768 PMCid:PMC11180069
11. Werner L, Roche R, Aletta F, Ma D, Singal H, John H, et al. London Assembly Call for Evidence on Progress on priorities: London's Environmental temperature check. 2026.
12. Saleem Khan M, Barratt B, Davies B, Simmonds NJ, Piel FB. Impact of air pollution on lung function in cystic fibrosis over a decade in London: a UK CF Registry study. thorax. 2026;81(9):845-52. https://doi.org/10.1136/thorax-2024-222710 PMid:41644139 PMCid:PMC13479626
13. Klapsa D, Wilton T, Zealand A, Bujaki E, Saxentoff E, Troman C, et al. Sustained detection of type 2 poliovirus in London sewage between February and July, 2022, by enhanced environmental surveillance. The Lancet. 2022;400(10362):1531-8. https://doi.org/10.1016/S0140-6736(22)01804-9 PMid:36243024 PMCid:PMC9627700
14. Organization WH. WHO global air quality guidelines: particulate matter (PM2. 5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide: executive summary: World Health Organization; 2021.
15. Khomenko S, Cirach M, Pereira-Barboza E, Mueller N, Barrera-Gómez J, Rojas-Rueda D, et al. Premature mortality due to air pollution in European cities: a health impact assessment. The Lancet Planetary Health. 2021;5(3):e121-e34. https://doi.org/10.1016/S2542-5196(20)30272-2 PMid:33482109
16. Sugarman GL. How the policy making process for air pollution reduction with particular reference to nitrogen dioxide can be improved to more effectively reduce school children's exposure in London: University of Surrey; 2024.
17. Gregg DJ, Tompkins J, Cordell RL, Brown AS, Smallbone KL, Vande Hey JD, et al. The impacts of the Ultra Low Emission Zone (ULEZ) and COVID-19 restrictions on air quality in central London-evidence for an increase in small particles. Atmospheric Environment. 2025:121668. https://doi.org/10.1016/j.atmosenv.2025.121668
18. Zoqi MJ, Dehqanpour Aliaqa A, Rasouli SJ, Mansouri Daneshvar MR. Daily PM2. 5 Prediction and Pollution Episode Detection Using MLP Neural Networks Across Urban Monitoring Sites with Varied Land Uses. Environmental Resources Research. 2026.
19. Khreis H, Williams M, Lad C, Fevyer D, Laverty AA, Jinks D, et al. The modelled impact of low traffic neighbourhoods (LTNs) on air pollution: findings from 5 schemes in London. Environmental Research. 2026:125093. https://doi.org/10.1016/j.envres.2026.125093 PMid:42342017
20. Wood HE, Hajmohammadi H, Dove RE, Scales J, Tsocheva I, Chavda J, et al. Impact of the Ultra Low Emission Zone on lung function growth in children in London, UK: a prospective parallel cohort study. The Lancet Public Health. 2026.
21. Chamberlain RC, Hodsoll J, Cai C, Griffiths C, Kelly F, Beevers S, et al. Association of vehicle emission charging zones with adult emergency hospital admissions: an interrupted time series analysis of the toxicity charge and Ultra Low Emission Zone in London, UK. Environment International. 2026:110324. https://doi.org/10.1016/j.envint.2026.110324 PMid:42214233
22. Font A, Guiseppin L, Blangiardo M, Ghersi V, Fuller GW. A tale of two cities: is air pollution improving in Paris and London? Environmental Pollution. 2019;249:1-12. https://doi.org/10.1016/j.envpol.2019.01.040 PMid:30875529
23. Angali KA, Farhadi M, Neisi A, Cheraghian B, Ahmadi M, Takdastan A, et al. The effect of consuming bread contaminated with heavy metals on cardiovascular disease and calculating its risk assessment. Scientific reports. 2025;15(1):2710. https://doi.org/10.1038/s41598-025-86240-3 PMid:39837925 PMCid:PMC11751297