Air Pollution: Exposures

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]

Air pollution can result from natural sources (dust, fires or volcanic eruptions) or human activities (motor vehicles and industrial facilities).

The most commonly examined air pollutant is particulate matter (PM), which is categorized by the size of particles, PM10 (<10μm) and PM2.5 (<2.5μm, also known as “fine particles”).

Other common pollutants are nitric oxides (NO_x), ozone (O₃), and sulphur dioxide (SO₂). Less commonly studied pollutants include carbon monoxide (CO), carbon dioxide (CO₂), black smoke, biomass smoke, environmental tobacco smoke (also known as passive smoke), synthetic gasses, hydrocarbons and dust.

Several studies referred to traffic-related air pollution; others used proxies of air pollution (e.g. volume of heavy goods vehicles, [Rugel 2020] proximity to industry or major roadways [Wray 2018] and the use of household fuels. [Zhang 2007] 

See also: Air Pollution: Interventions

Impact

All reviews found that exposure to air pollution had a strong negative impact on health. There was only one review with a meta-analysis; [Barnett 2018] exposures were associated with significant adverse events, including death.

Results

Twenty-one reviews examined the health impacts of air pollution from over 600 primary studies. Overall, exposure to air pollution had negative consequences on the respiratory, immune and cardiovascular systems, cancer, maternal health and birth outcomes, type 2 diabetes mellitus, weight, neurological diseases, mental health and death.

Exposure to air pollution was associated with 56 negative health outcomes across 16 disease categories.

For mortality outcomes, exposure to air pollution was associated with

• Premature death [Arantes 2019; Ali 2019]
• Cardiovascular mortality [Brunekreef 2005]
• Respiratory mortality [Oliveira 2011; Alaazi 2020]
• Non-specified mortality [Brunekreef 2005; Rugel 2020; Ali 2019; Coker 2018; Hesterberg 2009; Rojas-Rueda 2021]

For mental health outcomes, exposure to air pollution was associated with: 

• Depression [Barnett 2018; Bernardini 2020; Coker 2018; Rojas-Rueda 2021; Sampson 2020]
• Schizophrenia [Bernardini 2020; Rojas-Rueda 2021]
• Panic attacks, substance abuse disorders, and suicide attempts [Bernardini 2020]
• Dementia, autism, and attention-deficit/hyperactivity disorder [Rojas-Rueda 2021]

For physical health outcomes, exposure to air pollution was linked to: 

• Respiratory system
  • Asthma [Hesterberg 2009; Choo 2015; Kurt 2016; DePriest 2017; Rojas-Rueda 2021; De Longueville 2010]
  • Chronic Obstructive Pulmonary Disease (COPD) [Kurt 2016; Rojas-Rueda 2021; De Longueville 2010]
  • Bronchitis and Tuberculosis [Ali 2019]
  • Pneumonia [Ali 2019; Zhang 2007]  

• Cardiovascular disease
  • Stroke [Coker 2018; Ali 2019; Rojas-Rueda 2021]
  • Hypertension and cardiac arrhythmias [Ali 2019; Rojas-Rueda 2021]
  • Cardiac arrest [Rojas-Rueda 2021]
  • Coronary artery disease [Ali 2019]

• Maternal health and birth outcomes
  • Gestational diabetes mellitus and congenital neural tube defects [Rojas-Rueda 2021]
  • Low birth weight [Coker 2018; Ali 2019; Rojas-Rueda 2021]
  • Preterm birth [Ali 2019; Rojas-Rueda 2021]

• Type 2 diabetes mellitus [Dendup 2018; Rojas-Rueda 2021]
• Body weight status [An 2018; Rojas-Rueda 2021]
• The immune system [Arantes 2019], including the eye [Alaazi 2020] and ear infections [Rojas-Rueda 2021]
• Cancer, including the mouth, pharynx, larynx, breast, cervix and leukaemia [Rojas-Rueda 2021], lungs [Zhang 2007; Kurt 2016; Ali 2019; Rojas-Rueda 2021; Wray 2018], oesophagus [Zhang 2007; Rojas-Rueda 2021] and head and neck cancers [Zhang 2007]
• Neurological diseases, including Alzheimer’s and Parkinson’s disease [Rojas-Rueda 2021]

Strength of the evidence 

Four reviews used tools to assess the risk of bias or quality, which was judged moderate [An 2018; Barnett 2018; Dendup 2018] and very low [Rugel 2020] quality evidence. The majority of the reviews were ranked uncertain.

Resource Implications

Only one review reported on the economic costs of the health impacts of air pollution [Zhang 2014]. Between 2002 and 2009, Lanzhou, China, had economic losses of over a billion renminbi (RMB) (approximately £120 million) in most years, with the highest loss of 1.66 billion RMB (almost £200 million) in 2009.

Recommendations

1. Developing air monitoring networks will facilitate epidemiological studies and, if made publicly available, could enable stakeholders to monitor air pollution levels and make decisions accordingly. [Coker 2018]
2. Improving individualised data on air pollution exposure by increasing access and affordability of wearable technology might improve personalised data collection and inform health practices. [Wray 2018]
3. Cooperation involving multiple stakeholders, including the government, industry, energy companies and the public, to increase investment to reduce pollution [Kurt 2016]
4. Implement policies at schools (e.g. restricting traffic ) and in homes, taking into consideration the health of individuals and the areas where such buildings are built. [DePriest 2017]
5. Medical staff should consider the physical and social neighbourhood environment, including exposure to air pollution when assessing children and others with asthma. [DePriest 2017]

Related Resources

• 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
• 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

Alaazi 2020. “Understanding the Slum-Health Conundrum in Sub-Saharan Africa: A Proposal for a Rights-Based Approach to Health Promotion in Slums.” Global Health Promotion 27 (3): 65–72.

Muhammad Ubaid 2019. “A Systematic Review on Global Pollution Status of Particulate Matter-Associated Potential Toxic Elements and Health Perspectives in Urban Environment.” Environmental Geochemistry and Health 41 (3): 1131–62.

Ruopeng 2018. “Impact of Ambient Air Pollution on Obesity: A Systematic Review.” International Journal of Obesity  42 (6): 1112–26.

Arantes 2019. “Urban Forests, Air Quality and Health: A Systematic Review.” International Forestry Review 21 (2): 167–81.

Barnett 2018. “Relationships between the Neighborhood Environment and Depression in Older Adults: A Systematic Review and Meta-Analysis.” International Psychogeriatrics / IPA 30 (8): 1153–76.

Bernardini 2020. “Air Pollutants and Daily Hospital Admissions for Psychiatric Care: A Review.” Psychiatric Services  71 (12): 1270–76.

Brunekreef 2005. “Epidemiological Evidence of Effects of Coarse Airborne Particles on Health.” The European Respiratory Journal: Official Journal of the European Society for Clinical Respiratory Physiology 26 (2): 309–18.

Chua Poh 2015. “An Overview of Indoor Air Quality and Its Impact on Respiratory Health among Malaysian School-Aged Children.” Reviews on Environmental Health 30 (1): 9–18.

Coker 2018. “A Narrative Review on the Human Health Effects of Ambient Air Pollution in Sub-Saharan Africa: An Urgent Need for Health Effects Studies.” International Journal of Environmental Research and Public Health 15 (3). https://doi.org/10.3390/ijerph15030427.

De Longueville 2010. “What Do We Know about Effects of Desert Dust on Air Quality and Human Health in West Africa Compared to Other Regions?” The Science of the Total Environment 409 (1): 1–8.

Dendup 2018. “Environmental Risk Factors for Developing Type 2 Diabetes Mellitus: A Systematic Review.” International Journal of Environmental Research and Public Health 15 (1). https://doi.org/10.3390/ijerph15010078.

DePriest 2017. “Neighborhood-Level Factors Related to Asthma in Children Living in Urban Areas.” The Journal of School Nursing: The Official Publication of the National Association of School Nurses 33 (1): 8–17.

Hesterberg 2009. “Critical Review of the Human Data on Short-Term Nitrogen Dioxide (NO2) Exposures: Evidence for NO2 No-Effect Levels.” Critical Reviews in Toxicology 39 (9): 743–81.

Ozlem Kar 2016. “Pulmonary Health Effects of Air Pollution.” Current Opinion in Pulmonary Medicine 22 (2): 138–43.

Beatriz Fátima Alves de 2011. “A Systematic Review of the Physical and Chemical Characteristics of Pollutants from Biomass Burning and Combustion of Fossil Fuels and Health Effects in Brazil.” Cadernos de Saude Publica 27 (9): 1678–98.

Rojas-Rueda 2021. “Environmental Risk Factors and Health: An Umbrella Review of Meta-Analyses.” International Journal of Environmental Research and Public Health 18 (2). https://doi.org/10.3390/ijerph18020704.

Rugel, 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.” Environmental Research 185 (June): 109388.

Sampson, 2020. “Urbanization, Urbanicity, and Depression: A Review of the Recent Global Literature.” Current Opinion in Psychiatry 33 (3): 233–44.

Wray, 2018. “Smart Prevention: A New Approach to Primary and Secondary Cancer Prevention in Smart and Connected Communities.” Cities  79 (September): 53–69.

Zhang 2007. “Household Air Pollution from Coal and Biomass Fuels in China: Measurements, Health Impacts, and Interventions.” Environmental Health Perspectives 115 (6): 848–55.

Zhang 2014. “Air Quality in Lanzhou, a Major Industrial City in China: Characteristics of Air Pollution and Review of Existing Evidence from Air Pollution and Health Studies.” Water, Air, and Soil Pollution 225 (10). https://doi.org/10.1007/s11270-014-2187-3.