Air pollution is the contamination of indoor or outdoor environments by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere (WHO, 2022).
See also Air pollution: Exposures
The majority of reviews found that interventions for air pollution had a significant negative effect on health.
Six reviews examined the health impacts of interventions relating to air pollution and health.
One review detailed the interventions used to reduce air pollution, including bans on coal sales, congestion charges, and air quality regulation, which were shown to improve air quality and respiratory health as well as reduce mortality rates [Benmarhnia 2014].
Improvements in ambient air pollution (PM2.5, PM10, NO2, SO2, O3, total suspended particles (TSP)) were associated with lower rates of overall mortality, decreased birth complications, decreased cardiovascular disease and decreased adverse mental health outcomes [Salgado 2020].
Improvements in ambient air pollution (PM2.5, PM10, NO2, SO2, O3, total suspended particles (TSP)) and noise levels (Lden, Lnight) resulted in lower rates of mortality, as well as decreased numbers of birth complications chronic diseases such as cardiovascular, cancer and, respiratory and mental outcomes.
- One review found that the evidence regarding the impact of air pollution on body weight remains mixed [An 2018].
- Barnett 2018 review provided support for the potential influence of the neighbourhood environment. However, further research is needed.
Air pollution has been documented to change endothelial function, trigger inflammation and insulin resistance [Dendup et al. 2018]. However, most of the included studies in the review did not have information on indoor exposure and exposure outside of the neighbourhood. Almost all (>90%) studies were from developed countries, and therefore, because of the decline in pollution in these settings, there is only a modest effect.
Traffic-related air pollution (TRAP)
- Rugel 2020 review included 51 individual studies (TRAP and noise: n = 29; TRAP and natural spaces: n = 10; noise and natural spaces: n = 2; TRAP, noise, and natural spaces: n = 7; TRAP, noise, natural spaces, and walkability: n = 3)
Strength of the evidence
Strength of the evidence
Four reviews (19%) used tools to assess the risk of bias or quality, which had moderate [An 2018; Barnett 2018; Dendup 2018] and very low [Rugel 2020] quality evidence. The majority (81%) of reviews were ranked uncertain. To improve the evidence base, future research should
- Focus on at-risk or vulnerable and disadvantaged populations
- Account for individual and other environmental factors by using more robust study designs
- Develop standard definitions, methods, and measures for air pollutants and health outcomes (e.g. ICD-10 codes) to reduce heterogeneity and increase the ability to estimate pooled effects in meta-analyses
- Undertake studies in developing countries
Searches for evidence were conducted between 2002 and 2020 in a median of three databases (IQR: 2-4). Ten of the included studies were formal systematic reviews (one with a meta-analysis [Barnett et al. 2018], eight narrative/literature reviews, one umbrella review, one scoping review, and one integrative literature review.
Neither review reported on the effect of lowering air pollution reported on costs or resource implications.
- Policies for reducing air pollution should consider subpopulations that may be at greater risk of harm [Benmarhnia et al. 2014]
- Future research should consider equity when designing interventions to reduce air pollution for health improvements [Benmarhnia et al. 2014]
- WHO (2010): WHO Guidelines for indoor air quality: selected pollutants
- WHO (2014): WHO Guidelines for indoor air quality: Household Fuel combustion
- WHO (2021): Ambient (outdoor) air pollution
- WHO (2021): Household air pollution and health
- WHO (2021): WHO global air quality guidelines
- WHO (2022): News release – billions of people still breathe unhealthy air
- IQAir (2021): Interactive global map of 2021 PM2.5 concentrations by city
- Global Carbon Project (Accessed 2022): Global Carbon Atlas
- OECD: Air pollution effects
- UK Government: Clean Air Strategy 2019
- UK Department for Environment, Food & Rural Affairs (2018): Air quality – explaining air pollution – at a glance
- Healthy Air (2022): Clean Air Consultation Tool
Clean Air Fund (2022): The Pathway to Healthy Air in the UK
References to reviews
References to reviews
An R 2018. Impact of ambient air pollution on obesity: a systematic review. Int J Obes (Lond). 2018 Jun;42(6):1112-1126. doi: 10.1038/s41366-018-0089-y. Epub 2018 May 24. PMID: 29795462.
Barnett A 2018. Relationships between the neighborhood environment and depression in older adults: a systematic review and meta-analysis. Int Psychogeriatr. 2018 Aug;30(8):1153-1176. doi: 10.1017/S104161021700271X. Epub 2017 Dec 10. PMID: 29223174.
Benmarhnia T 2014. “Addressing Equity in Interventions to Reduce Air Pollution in Urban Areas: A Systematic Review.” International Journal of Public Health 59 (6): 933–44.
Dendup T 2018 Environmental Risk Factors for Developing Type 2 Diabetes Mellitus: A Systematic Review. Int J Environ Res Public Health. 2018 Jan 5;15(1):78. doi: 10.3390/ijerph15010078.
Rugel EJ 2020. Quiet, clean, green, and active: A Navigation Guide systematic review of the impacts of spatially correlated urban exposures on a range of physical health outcomes. Environ Res. 2020 Jun;185:109388. doi: 10.1016/j.envres.2020.109388.
Salgado M 2020. Environmental determinants of population health in urban settings. A systematic review. BMC Public Health, 2020