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EVIDENCE

HEALTH BURDEN

 

GLOBAL HEALTH BURDEN AND THE EFFECTS OF AIR POLLUTION ON RESPIRATORY HEALTH

Air pollution is the world’s largest environmental risk to health,1 and a major cause of disease and premature death.2

Ambient (outdoor) and household (indoor) air pollution both contribute to the global burden. Emissions from transport, industry, power generation and agricultural processes affect both cities and rural areas and, according to estimates from the World Health Organization, 9 out of 10 of people worldwide breathe polluted air.2

Within the home, 3 billion people are at risk of household air pollution from use of unclean fuels and technologies for cooking and heating.3

Several common pollutants are harmful to health. However, ambient particulate matter ─ a complex mixture of solid and liquid particles suspended in air ─ is of particular concern, and levels of particulate matter are a key indicator of air quality and health risk.4

The respiratory system, as the first point of contact with inhaled pollutants, is uniquely vulnerable, but air pollution also affects the cardiovascular system and other aspects of health.5 Studies are continuing to identify causal associations of air pollutants with adverse health outcomes, and to uncover plausible biological mechanisms for these effects. The impact of air pollution on quality of life,6 and the effects of climate change on air pollution and health, are other important areas of study.

Here, The Clean Breathing Institute discusses the global burden of air pollution and the effects of air pollution on respiratory health.

 

asian female

WHAT IS AIR POLLUTION?

Air pollution mainly results from human activity and is a complex mix of solid, liquid and gas particles from both ambient (outdoor) and household (indoor) sources.5,7 Ambient sources include combustion of fossil fuels, road traffic and industry. Household sources can include fuels such as biomass, coal and kerosene used for cooking, heating and lighting.5,7 Important gaseous pollutants include volatile organic compounds (VOCs) such as benzene.5 Indoor sources of VOCs include construction materials, furnishing, paints, glues, heating appliances, tobacco smoke and cleaning products.8 Air pollution can also arise from natural sources such as dust, pollen and wildfires.5,9

Air pollution is a mixture of solid, liquid and gas particles suspended in the air4,9 and may include components such as ozone, nitrogen oxides, carbon monoxide and sulphur dioxide, metals, organic chemicals and biological materials.5,9

Particulate matter is used as an indicator of air pollution and is usually divided into groups based on particle size (Figure 1):5,9–12

 

  • Coarse particulate matter has an aerodynamic diameter of between 10 μm and 2.5 μm, and is referred to as PM10–2.5
  • Fine particulate matter has an aerodynamic diameter of less than 2.5 μm and is referred to as PM2.5
  • Ultrafine particulate matter has an aerodynamic diameter of less than 0.1 μm and is referred to as PM0.1

 

Fine (PM2.5) and ultrafine (PM0.1) particulate matter are associated with the greatest health risks, as they can travel deeper into the airways, reaching distal regions of the lungs, where water-soluble components can enter the bloodstream by translocating through alveolar capillaries (Figure 1).11,12  PM2.5 is commonly used as an indicator of global air pollution by organisations such as the World Health Organization.4

 

Particulate matter

Figure 1. Particulate matter in air pollution.5,10–21 

 

Global burden of air pollution

Ambient (outdoor) and household (indoor) air pollution cause an estimated 7 million premature deaths each year,22 including approximately 600,000 deaths per year in children under 5 years of age.23 Outside the home, incineration and combustion of fossil fuels emit a complex array of pollutants, including particulate matter, nitrogen dioxide, sulphur dioxide and carbon monoxide, which may react in the air to generate secondary pollutants, such as ground-level ozone. In 2016, 91% of the global population lived in places that did not meet the World Health Organization’s (WHO) air quality guideline levels for particulate matter,4 and more than 50% lived in cities with at least 2.5 times the recommended levels of fine particulate matter.24 The latest air quality data from over 100 countries can be viewed on the WHO interactive map.25

Ambient air pollution

Exposure to ambient air pollution was estimated to cause 4.2 million premature deaths worldwide in 2016.4 In 2015, the Global Burden of Diseases study identified ambient PM2.5 (particulate matter with diameter <2.5 μm) as responsible for 7.6% of total global mortality ─ this makes it the fifth most important global risk factor for death.26  

Ambient air pollution affects all geographical regions and countries, and people of all socioeconomic groups.22 However, low- and middle-income (LMI) countries are the most affected, with the poorest air quality in Eastern Mediterranean and African regions.24 In 2016, 91% of deaths linked to ambient air pollution occurred in LMI countries, with the highest numbers in South-East Asia and Western Pacific regions.4

Household air pollution

Household air pollution is another major cause of premature death. Around 3 billion people still cook using solid fuels or kerosene in inefficient stoves or open hearths.3 This releases particulate matter, methane, carbon monoxide, polyaromatic hydrocarbons and volatile organic compounds into the home,27 and also contributes to ambient air pollution. Each year, 3.8 million people die prematurely as a result of household air pollution.3

Household air pollution from cooking fuels is strongly linked to poverty, with rural households in Sub-Saharan Africa, South and East Asia and the Western Pacific experiencing the greatest health burden.27 This interactive graph28 shows mortality from household and ambient air pollution in WHO regions and countries.

 

 

Impact of air pollution on health

The effects of ambient (outdoor) and household (indoor) air pollution on human health are wide-ranging. Inhalation of airborne pollutants damages the respiratory tract, reduces lung function, and causes or exacerbates acute and chronic respiratory diseases, including asthma.5 More than 25% of premature deaths associated with air pollution are respiratory in nature.12

 

Outdoor air pollution and particulate matter are classed as carcinogenic to humans29 and exposure to air pollution is estimated to cause 29% of all adult deaths from lung cancer.2 It is estimated that air pollution causes 43% of all adult deaths from chronic obstructive pulmonary disease, 25% from stroke and 24% from heart disease.2 Household air pollution is responsible for nearly half (45%) of all pneumonia deaths in children under 5 years of age and contributes to 28% of pneumonia deaths in adults.3 There is mounting evidence for the adverse effects of prenatal exposure to air pollution on lung development, respiratory health and development of chronic disease in adulthood.30 BreatheLife – a joint campaign led by the World Health Organization (WHO), United Nations Environment, and Climate & Clean Air Coalition – provides tips on reducing prenatal exposure.31

In recent years, evidence for effects of inhaled pollutants on the central nervous system has also emerged. Exposure to air pollution has been associated with impaired cognitive and psychomotor development in children, and with cognitive decline and dementia in the elderly.32

Click here to learn more about the mechanisms through which air pollution leads to adverse health effects.

Why breathing clean air is important

Life-time exposure to ambient air pollution, in a highly polluted city such as Beijing in China, may result in an estimated loss of life expectancy of approximately 3 years.33,34 Other estimates suggest that long-term exposure to air pollution may reduce life expectancy by as much as 11 years (based on WHO consensus estimates for the mortality risk ratio related to an annual PM2.5 increase of 10 μg/m3).35

By reducing air pollution in cities to WHO air quality guideline levels (PM2.5 annual mean concentrations reduced to 10 μg/m3), air pollution-related deaths could be reduced by 15%.4

The Energy Policy Institute at the University of Chicago have estimated the extra life gained per person if air pollution in major cities met WHO air quality guideline levels:36

 

 

United Kingdom

150

<1 month

United States

US flag

1.6 months

Poland

Poland flag

1.3 years

China

China flag

3 years

India

India flag

4 years 

 

Evidence for health impacts of common air pollutants

Particulate matter

There is a well-documented causal link between exposure to particulate matter (especially PM2.5) and cardiorespiratory health outcomes and mortality, although effect sizes vary across studies, location and season.37 In a meta-analysis of the effects of short-term exposure to PM2.5 constituents, the strongest associations with mortality were observed for elemental carbon and potassium.37 Studies are uncovering the biological mechanisms for the effects of particulate matter on cardiorespiratory health, including modulation of the airway epithelium and induction of specific cytokine pathways in asthma,38 promotion of oxidative stress in atherosclerosis,13 and mechanisms relating to cell death.39  

Ground-level ozone

Ground-level ozone (O3), a constituent of photochemical smog, can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases.4 Short-term exposure is associated with mortality and hospitalisation, and there is growing evidence for the effects of long-term exposure on respiratory and cardiorespiratory mortality in warm-season months.40 Ozone exposure may also have metabolic effects.41

Nitrogen dioxide

Short- and long-term exposure to nitrogen dioxide (NO2) has been associated with mortality, hospital admissions and respiratory symptoms, including among asthmatic children.42,43 However, it is difficult to identify a direct effect of NO2 exposure due to its strong correlation with other air pollutants.43  

Sulphur dioxide

Sulphur dioxide (SO2) can inflame the respiratory tract, affect lung function, and irritate the eyes; changes in lung function and respiratory symptoms may arise in people with asthma after just 10 minutes of exposure.4 SO2 has also been associated with cardiac disease hospitalisation and mortality.4

Co-exposure to pollutants

Alongside studies of individual pollutants, there are increasing efforts to understand the real-world complexity of the interactive effects of exposure to more than one inhalent – for example, effects of co-exposure to air pollutants plus aeroallergens on respiratory tract function.44,45 The interaction of physical activity and air pollution on cardiorespiratory health,46,47 and effects of climate change on air quality and health,40 are further areas of current study. 

 

Impact of air pollution on quality of life (QoL)

Clean air is a basic human requirement. Air quality and risk to health can affect physical, mental, and social well-being,6 although further studies are needed to fully elucidate the impact of air pollution on QoL. Health-related QoL is impacted by pollution-related symptoms, diseases, and exacerbations of existing respiratory conditions.48–50 Beyond the physical effects, studies have shown that air quality is an important determinant of subjective well-being, which encompasses individuals’ life satisfaction, happiness and optimism.6 Exposure to air pollution has been linked to impaired subjective well-being.51–57

Daily life is also affected - air pollution has been associated with reduced productivity,58,59 lower daily activity scores and lower social functioning,49 and may entail avoidance of physical outdoor activity to limit exposure. Pollution-induces cognitive deficits in children and adults60 and this may further impact QoL.

Download our literature review and our advisory meeting summary to find out more about the global burden of air pollution and the effects of air pollution on respiratory health.

 

  • REFERENCES

    01. World Health Organization. Ambient and household air pollution and health database. Available at: http://www.who.int/phe/health_topics/outdoorair/databases/en/. Last accessed: 23 July 2018.

    02. World Health Organization. News release. Available at: http://www.who.int/news-room/detail/02-05-2018-9-out-of-10-people-worldwide-breathe-polluted-air-but-more-countries-are-taking-action. Last accessed: 23 July 2018.

    03. World Health Organization. Household air pollution and health. Available at: http://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health. Last accessed: 23 July 2018.

    04. World Health Organization. Ambient (outdoor) air quality and health. Available at: http://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health. Last accessed: 18 July 2018.

    05. Kampa M, Castanas E. Human health effects of air pollution. Environ Pollut 2008;151:362–7.

    06. Darçın 2017. How air pollution affects subjective well-being. Available at: http://dx.doi.org/10.5772/67742. Last accessed: 23 July 2018.

    07. World Health Organization. Air pollution and health: summary. Available at: http://www.who.int/airpollution/ambient/about/en/. Last accessed: 22 July 2018.

    08. Paciência I, et al. A systematic review of evidence and implications of spatial and seasonal variations of volatile organic compounds (VOC) in indoor human environments. J Toxicol Environ Health B Crit Rev 2016;19(2):47–64.

    09. D'Amato G, et al. Urban air pollution and climate change as environmental risk factors of respiratory allergy: an update. J Investig Allergol Clin Immunol 2010;20:95–102; quiz following 102.

    10. Australian Government. Health Impacts of Ultrafine Particles, 2004. Available at: https://www.environment.gov.au/system/files/resources/00dbec61-f911-494b-bbc1-adc1038aa8c5/files/health-impacts.pdf. Last accessed: 24 July, 2018.

    11. Huang S–K, et al. Mechanistic impact of outdoor air pollution on asthma and allergic diseases. J Thorac Dis 2015;7:23–33.

    12. Traboulsi H, et al. Inhaled pollutants: the molecular scene behind respiratory and systemic diseases associated with ultrafine particulate matter. Int J Mol Sci 2017;18:243.

    13. Araujo JA, Nel AE. Particulate matter and atherosclerosis: role of particle size, composition and oxidative stress. Part Fibre Toxicol 2009;6:24.

    14. Environmental Protection Agency. Particle pollution and your health. Available at: https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1001EX6.txt. Last accessed: 22 July 2018.

    15. Interprofessional Technical Centre for Studies on Air Pollution (CITEPA). Particulate matter. Available at: https://www.citepa.org/en/air-and-climate/pollutants-and-ghg/particulate-matter. Last accessed: 22 July 2018.

    16. Salvi S, Holgate ST. Mechanisms of particulate matter toxicity. Clin Exp Allergy 1999;29:1187–94.

    17. Cooper SC. The Truth about Mold. Dearborn Financial Publishing: Chicago, IL; 2004.

    18. Alessandrini ER, et al. Association Between Short-Term Exposure to PM2.5 and PM10 and Mortality in Susceptible Subgroups: A Multisite Case-Crossover Analysis of Individual Effect Modifiers. Am J Epidemiol 2016;184(10):744–54.

    19. World Health Organization. Frequently Asked Questions. Available at: http://www.who.int/airpollution/data/FINAL-FAQs-WEB-Database-2018.pdf. Last accessed: 23 July 2018.

    20. World Health Organization. Health effects of particulate matter. Available at: http://www.euro.who.int/__data/assets/pdf_file/0006/189051/Health-effects-of-particulate-matter-final-Eng.pdf. Last accessed: 25 July 2018.

    21. Xing YF, et al. The impact of PM2.5 on the human respiratory system. J Thorac Dis 2016;8(1):E69–74.

    22. World Health Organization. Burden of disease from the joint effects of household and ambient air pollution for 2016. Available at: http://www.who.int/airpollution/data/AP_joint_effect_BoD_results_May2018.pdf. Last accessed: 23 July 2018.

    23. World Health Organization. Don’t pollute my future! The impact of the environment on children’s health (updated May 2018). Available at: http://www.who.int/ceh/publications/don-t-pollute-my-future/en/. Last accessed: 23 July 2018.

    24. World Health Organization. Frequently Asked Questions. Available at: http://www.who.int/airpollution/data/FINAL-FAQs-WEB-Database-2018.pdf. Last accessed: 23 July 2018.

    25. World Health Organization. Global ambient air pollution: interactive map. Available at: http://maps.who.int/airpollution/. Last accessed: 23 July 2018.

    26. Cohen AJ, et al. Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015. Lancet 2017;13;389(10082):1907–18.

    27. World Health Organization. Household air pollution: health impacts. Available at: http://www.who.int/airpollution/household/health-impacts/en/. Last accessed: 23 July 2018.

    28. World Health Organization. Global ambient air pollution: world health statistics data visualizations dashboard. Available at: http://apps.who.int/gho/data/node.sdg.3-9-viz-1?lang=en. Last accessed: 23 July 2018.

    29. World Health Organization, International Agency for Research on Cancer. Outdoor air pollution a leading environmental cause of cancer deaths (press release). Available at: https://www.iarc.fr/en/media-centre/iarcnews/pdf/pr221_E.pdf. Last accessed: 23 July 2018.

    30. Korten I, et al. Air pollution during pregnancy and lung development in the child. Paediatr Respir Rev 2017;21:38–46.

    31. Environmental Protection Agency. Air Pollution and Pregnancy. Available at: http://breathelife2030.org/wp-content/uploads/2016/09/ochp_prenatal_fs_7_10.pdf. Last accessed: 22 July 2018.

    32. de Prado Bert P, et al. The effects of air pollution on the brain: a review of studies interfacing environmental epidemiology and neuroimaging. Curr Environ Health Rep 2018;doi:10.1007/s40572-018-0209-9.

    33. Dockery DW, Pope CA III. Lost life expectancy due to air pollution in China. Available at: http://institute.swissre.com/research/risk_dialogue/magazine/Cardiovascular_risks_in_HGM/Lost_life_expectancy_due_to_air_pollution_in_China.html. Last accessed: 22 July 2018.

    34. Pope CA III, Dockery DW. Air pollution and life expectancy in China and beyond. Proc Natl Acad Sci USA 2013;110:12861–2.

    35. Andersen, MS. Co-benefits of climate mitigation: counting statistical lives or life-years? Ecol Indic 2017;79:11–8.

    36. Energy Policy Institute at the University of Chicago. Air Quality Life Index. Available at: https://aqli.epic.uchicago.edu/. Last accessed: 18 July 2018.

    37. Achilleos S, et al. Acute effects of fine particulate matter constituents on mortality: a systematic review and meta-regression analysis. Environ Int 2017;109:89–100.

    38. de Grove KC, et al. Insights in particulate matter-induced allergic airway inflammation: focus on the epithelium. Clin Exp Allergy 2018;48:773–86.

    39. Peixoto MS, et al. Cell death pathways of particulate matter toxicity. Chemosphere 2017;188:32–48.

    40. Doherty RM, et al. Climate change impacts on human health over Europe through its effect on air quality. Environ Health 2017;16(Suppl 1):118.

    41. Thomson EM, et al. Ozone inhalation provokes glucocorticoid-dependent and -independent effects on inflammatory and metabolic pathways. Toxicol Sci 2016;152:17–28.

    42. Atkinson RW, et al. Long-term concentrations of nitrogen dioxide and mortality: a meta-analysis of cohort studies. Epidemiology 2018;29:460–72.

    43. World Health Organization. Review of evidence on health aspects of air pollution – REVIHAAP project: technical report. Available at: http://www.euro.who.int/en/health-topics/environment-and-health/air-quality/publications/2013/review-of-evidence-on-health-aspects-of-air-pollution-revihaap-project-final-technical-report. Last accessed: 23 July 2018.

    44. Carlsten C. Synergistic environmental exposures and the airways capturing complexity in humans-an underappreciated world of complex exposures. Chest 2018;pii:S0012–3692(18)30915–2.

    45. Rodopoulou S, et al. Assessing the cumulative health effect following short term exposure to multiple pollutants: an evaluation of methodological approaches using simulations and real data. Environ Res 2018;165:228–34.

    46. Laeremans M, et al. Short-term effects of physical activity, air pollution and their interaction on the cardiovascular and respiratory system. Environ Int 2018;117:82–90.

    47. Sinharay R. Respiratory and cardiovascular responses to walking down a traffic-polluted road compared with walking in a traffic-free area in participants aged 60 years and older with chronic lung or heart disease and age-matched healthy controls: a randomised, crossover study. Lancet 2018;391:339–49.

    48. Nakao M, et al. Effects of air pollution and seasons on health-related quality of life of Mongolian adults living in Ulaanbaatar: cross-sectional studies. BMC Public Health 2017;17:594.

    49. Nakao M, et al. The impact of air pollution, including Asian sand dust, on respiratory symptoms and health-related quality of life in outpatients with chronic respiratory disease in Korea: a panel study. J Prev Med Public Health 2018;51:130–9.

    50. Pirozzi CS, et al. Short-term particulate air pollution exposure is associated with increased severity of respiratory and quality of life symptoms in patients with fibrotic sarcoidosis. Int J Environ Res Public Health 2018;15:pii:E1077.

    51. Bose S, et al. Association of traffic air pollution and rhinitis quality of life in Peruvian children with asthma. PLoS One 2018;13:e0193910.

    52. Orru K, et al. Well-being and environmental quality: does pollution affect life satisfaction? Qual Life Res 2016;25:699–705.

    53. Ferreira S, et al. Life satisfaction and air quality in Europe. Ecol Econ 2013;88:1–10.

    54. Smyth R, et al. The environment and well-being in urban China. Ecol Econ 2008;68:547–55.

    55. MacKerron G, Mourato S. Life satisfaction and air quality in London. Ecol Econ 2009;68:1441–53.

    56. Cuñado J, Pérez de Gracia F. Environment and happiness: new evidence for Spain. Soc Indic Res 2013;112:549–67.

    57. Zhang X, et al. Happiness in the air: how does a dirty sky affect mental health and subjective well being? J Environ Econ Manage 2017;85:81–94.

    58. Zivin JG, Neidell M. The Impact of Pollution on Worker Productivity. Am Econ Rev 2012;102(7):3652–73.

    59. Lichter A, Pestel N, Sommer E. Productivity effects of air pollution: Evidence from professional soccer. Labour Economics 2017;48:54–66.

    60. Allen JL, et al. Cognitive effects of air pollution exposures and potential mechanistic underpinnings. Curr Environ Health Rep 2017;4:180–91.

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