Air Pollution

Worldwide, pollution is a leading cause of death and causes substantial economic damage.

Source: Landrigan et al. ¹.

In wealthier countries such as the United States, better technology and tighter pollution controls have helped reduce the damage.

Source: Muller ².

Particulates

Worldwide, particulate pollution is generated across the economy, especially from home combustion of biomass and coal. Forest and savannah fires are the major natural source of particulates.

Sources of world particulate emissions as of 2010. Source: Klimont et al. ³.

As of 2011, particulate air pollution in the United States caused nearly $900 billion in annual damages.

Source: Goodkind et al. ⁴.

Damages from air pollution depend both on the nature of the pollutant and where it is released; generally, pollutants released in high population density areas do more damage. Following are estimated monetized damage from particulate pollution by source.

Source: Goodkind et al. ⁴.

Indoor Air Pollution

Indoor air pollution contributes to 1.6 million ⁵ to 2.9 million ¹ deaths per year. The main source of indoor air pollution is cooking, particularly with traditional biofuels in poor countries, and the death toll is trending down with development ⁶.

Source: Edwards et al. ⁷.

Acidification

Freshwater and soil acidification are the reduction of pH in water and the soil, a process that harms ecosystems and soil fertility. Acid rain, a form of acidification, further harms ecosystems and buildings. Three main gases--sulfur dioxide (SO₂), nitrogen oxides (NOx), and ammonia--are artificial causes of acidification, though some other gases play smaller roles ⁸.

Data on ammonia and NOx emissions may be unreliable due to age and difficulty of data collection. Sources: NOx from the UN ⁹, SO₂ from Dahiya and Myllyvirta ¹⁰, NH3 from Sutton et al. ¹¹, and acidification potentials from Lindley et al. ⁸.

Following are estimates of major sources of sulfur dioxide and ammonia emissions worldwide and nitrogen oxide emissions in the United States.

World sources of SO₂ emissions as of 2018. Source: Dahiya and Myllyvirta ¹⁰

Figures are as of 2008, except for emissions from application of fertilizer, which are as of 2000. Source: Sutton et al. ¹¹.

Source: U.S. EPA ¹².

Due to pollution controls, NOx emissions in the United States ¹², and SO₂ emissions in the United States and China ¹⁰ are trending down.

Aerosol Loading

Aside from direct impacts on human health, atmospheric aerosols have effects on the climate that are not yet fully understood. Current natural and human-caused aerosol emissions are estimated as follows.

Source: Tomasi and Lupi ¹³.

Most major classes of aerosols should cause short-term global cooling, by reflecting more sunlight than they absorb. The exception is black carbon, which causes warming ¹⁴. A major source of uncertainty in the impact of aerosols is in their interaction with cloud formation ¹⁴. If all aerosols from human activity were to cease, the result would be an estimated 0.5℃ to 1.1℃ global warming and a 2-4.6% increase in precipitation ¹⁵, in contrast to the nearly 1℃ observed since the start of industrialization and 2℃ target set by the Paris Agreement. The cooling effect motivates interest in intentionally releasing aerosols into the upper atmosphere to offset global warming.

Air Pollution Removal

Several methods are considered to remove air pollution from the ambient atmosphere. Among them are smog towers, or air purification towers; photocatalysts such as titanium dioxide; or biological methods such as tree planting or living walls ¹⁶.

Titanium dioxide is effective in removing nitrous oxides and volatile organic compounds from the atmosphere, but not carbon monoxide. The use of titanium dioxide coatings on buildings and other urban surfaces does not appear to be cost effective at present ¹⁷. Research is ongoing into chemical modifications that might be more effective ¹⁸. Smog towers have been deployed recently in highly polluted cities in India, China, and Poland, and their cost-effectiveness in reducing air pollution is not firmly established ¹⁹.

References

1. Landrigan, P. et al. "The Lancet Commission on pollution and health". The Lancet Commissions 391(10119), pp. 462-512. February 2018. ↩ ↩²

2. Muller, N. Z. "Long-Run Environmental Accounting in the U.S. Economy". Environmental and Energy Policy and the Economy 1. 2020. ↩

3. Klimont, Z., Kupiainen, K., Heyes, C., Purohit, P., Cofala, J., Rafaj, J., Borken-Kleefeld, J., Schöpp, W. "Global anthropogenic emissions of particulate matter including black carbon". Atmospheric Chemistry and Physics Discussions 17(14), pp. 8681–8723. 2017. ↩

4. Goodkind, A., Tessum, C., Coggins, J., Hill, J., Marshall, J. "Fine-scale damage estimates of particulate matter air pollution reveal opportunities for location-specific mitigation of emissions". Proceedings of the National Academy of Sciences of the United States of America 116(18), pp. 8775-8780. April 2019. ↩ ↩²

5. Global Burden of Disease Collaborative Network. "Global Burden of Disease Study 2017 (GBD 2017) Results". Seattle, United States: Institute for Health Metrics and Evaluation (IHME). 2018. ↩

6. Ritchie, H., Roser, M. "Indoor Air Pollution". Our World in Data. Rev. November 2019. ↩

7. Edwards, R., Karnani, S., Fisher, E., Johnson, M., Naeher, L., Smith, K., Morawska, L. "Review 2: Emissions of Health-Damaging Pollutants from Household Stoves". WHO Indoor Air Quality Guidelines: Household fuel Combustion. November 2014. ↩

8. Lindley, A., McCulloch, A., Vink, T. "Contribution of Hydrofluorocarbons (HFCs) and Hydrofluoro-Olefins (HFOs) Atmospheric Breakdown Products to Acidification ("Acid Rain") in the EU at Present and in the Future". Open Journal of Air Pollution 8, pp. 81-95. 2019. ↩ ↩²

9. United Nations. "Environmental Indicators Of Air Pollution: NOx Emissions". Harvard Dataverse, V2. 2015. ↩

10. Dahiya, S., Myllyvirta, L. "Global SO₂ emission hotspot database: Ranking the World's Worst Sources of SO₂, Pollution". Greenpeace Environment Trust. August 2019. ↩ ↩² ↩³

11. Sutton, M. et al. "Towards a climate-dependent paradigm of ammonia emission and deposition". Philosophical Transactions of the Royal Society B: Biological Sciences 368(1621): 20130166. July 2013. ↩ ↩²

12. U. S. Environmental Protection Agency. "2014 National Emissions Inventory (NEI) Data". Accessed May 10, 2020. ↩ ↩²

13. Tomasi, C., Lupi, A. Primary and Secondary Sources of Atmospheric Aerosol. Chapter 1, Atmospheric Aerosols: Life Cycles and Effects on Air Quality and Climate. November 2016. ↩

14. Boucher, O., Randall, D., Artaxo, P., Bretherton, C., Feingold, G., Forster, P, Kerminen, V.-M., Kondo, Y., Liao, H., Lohmann, U., Rasch, P., Satheesh, S. K., Sherwood, S., Stevens, B., Zhang, X. Y. "Clouds and Aerosols". In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [^Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]:. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 2013. ↩ ↩²

15. Samset, B. H., Sand, M., Smith, C. J., Bauer, S. E., Forster, B. M., Fuglestvedt, J. S., Osprey, S., Schleussner, C.-F. "Climate Impacts From a Removal of Anthropogenic Aerosol Emissions". Geophysical Research Letters 45(2), pp. 1020-1029. January 2018. ↩

16. Stanaszek-Tomal, E. "Anti-Smog Building and Civil Engineering Structures". Processes 9(8), 1446. August 2021. ↩

17. Barkalow, G., Chambers, B., Spiegel, L., Birkinshaw, K., Krebs, M., Jones, M. "Evaluation of Titanium Dioxide as a Photocatalyst for Removing Air Pollutants". Prepared by Lawrence Berkeley National Laboratory, for the California Energy Commission. January 2008. ↩

18. Russell, H. S., Frederickson, L. B., Hertel, O., Ellermann, T., Jensen, S. S. "A Review of Photocatalytic Materials for Urban NOx Remediation". Catalysts 11(6), 675. May 2021. ↩

19. Guttikunda, S., Jawahar, P. "Can We Vacuum Our Air Pollution Problem Using Smog Towers?". Atmosphere 11(9), 922. August 2020. ↩