Air pollution is one of the leading causes of death around the world. The pollution in a city is measured in terms of the density of fine particulate matter. Fine particulate matter is defined as particles of air pollutants with an aerodynamic diameter less than 2.5 micrometers (PM2.5). These are tiny particles in the air that reduce visibility and cause the air to appear hazy as the density of them goes higher. Here is the list of the top 10 least polluted cities in World ranked in 2021.

10 world's least polluted cities in 2021 - Sheet1
India Gate, Delhi (Lesser PM2.5) 2019 and (Higher PM2.5) 2020_©Anushree Fadnavis, Adnan Abidi

1. Zurich, Switzerland (0.51µg/m3) | Least polluted cities in world

Zurich is the least polluted city in 2021 and is recognized for its clean air. It is due to the strict policy design of the city to reduce pollution from vehicles, the promotion of cleaner forms of transport, and low levels of air pollution. The citizens widely use cycles, trains, and subways instead of driving. The city also has a strong commitment to waste management. They provide an app to track and manage garbage and its recycling.

10 world's least polluted cities in 2021 - Sheet2
Cycling in Zurich_©Depositphotos

2. Hobart, Australia (2.73µg/m3)

The city of Hobart has been taking sustainability and climate considerations into its decision-making processes and operations for two decades. It has measured and significantly reduced its energy consumption and greenhouse gas emissions, utilizing scientific and evidence-based reasoning to set policy, identify barriers and create opportunities. The city is concentrating on solar energy for electricity to reduce emissions. The city also integrated autonomous sensor networks to storm water drainage to detect plastics, cans, leaves and prevent them from reaching the ocean.

10 world's least polluted cities in 2021 - Sheet3
Hobart, Australia_©Tasmanian Airtours

3. Reykjavik, Iceland (3.68µg/m3) | Least polluted cities in world

Heavy industry in Iceland contributes 48% of the country’s carbon dioxide (CO2) emissions, according to the Environment Agency of Iceland, excluding greenhouse gases from land use and forestry. According to the magazine Reykjavik Grapevine in 2019, Iceland suffered from heavy air pollution. But Reykjavik, the capital of Iceland, is the third least polluted city in the world in 2021. Reykjavik is using an automated system of pot rooms, which plays a crucial role in reducing carbon emissions. Sometimes the carbon gases are injected into the basalt rocks, which turns CO2 into minerals. Reykjavik also reduced the use and increased the recycling of plastics. The city focuses on the prevention of marine litter into the ocean and they also took efforts to enhance the knowledge on the effects of micro plastics on humans and identify measures to control and prevent their discharge to oceans.

10 world's least polluted cities in 2021 - Sheet4
Reykjavik_©Toshio Kishiyama

4. Launceston, Australia (3.68µg/m3)

The geographic position of Launceston makes it subject to an inversion layer, making the air warmer. Being hilly, the people in the city are used to fireplaces and wooden heaters, which led to high smoke and pollution in the atmosphere of Launceston. Community education campaigns, enforcement of environmental regulations, and a wood heater replacement programme that encouraged the use of electric heaters as an alternative, helped in reducing pollution and becoming one of the least polluted cities in 2021.

10 world's least polluted cities in 2021 - Sheet5
Launceston, Australia_©City of Launceston

5. Honolulu, US (3.68µg/m3) | Least polluted cities in world

Though Hawaii suffers from air pollution, Honolulu is the cleanest city in Hawaii. The climatic conditions of the city and its population density help keep the air clean. Relatively less heavy industries also contribute to the lesser pollution. However, the solid waste (marine debris) has been increasing in the city and strategies are being taken to remove the debris.

Least polluted cities in world - Sheet6
Honolulu, US_©Artwager

6. Vitoria, Brazil (4.10 µg/m3)

Vitoria has been recognised for its growth in human and economic development, quality of life, education and health services, and transparency in various national rankings. The largest industrial projects carried out in Vitoria were the main source of pollution in the city. But now, Vitoria is one of the few cities of Brazil, which has been included in the Emerging and Sustainable Cities (ICES). This is a result of the formation and execution of an environmental management system that controlled the environmental liabilities such as water and soil polluted by hydrocarbons from industries, proper sanitation, etc. 

Least polluted cities in world- Sheet7
Vitoria, Brazil_©WorldAtlas

7. Bergen, Norway (4.39 µg/m3)

The city of Bergen, Norway enjoys crisp blue skies and crystal-clear views of the region’s scenic beauty. Situated in the valleys, it is an isolated city without heavy industries which causes high particle emissions. However, like Los Angeles and Launceston, temperature inversions often act as a lid over the city, trapping all emissions from the cars and buildings below. These emissions come from powered vehicles and fireplaces, and wood stoves. But, with the promotion of electric cars and zero-emission vehicles and the ban on wood furnaces, the air quality of the city is the best in the last few years.

Least polluted cities in world- Sheet8
Bergan, Norway_©pxleyes

8. Wollongong, Australia (4.48 µg/m3) | Least polluted cities in world

Wollongong is one of the largest cities with the least pollution. The major sources of air pollution in Wollongong were coal-fired power stations, coal mines, and on- and off-road transport emissions – as well as heavy industry, the chemical industry, and bushfires. With the elimination of coal mines and the promotion of alternative energy sources, Wollongong became one of the least polluted cities in the world. 

Least polluted cities in world- Sheet9
Wollongong, Australia_©Chilby Photography

9. Turku, Finland (4.51 µg/m3)

Turku is the oldest and the most sustainable city in Finland, which aims to make history with carbon neutrality in 2029. To achieve this, the city is placing a strong focus on the Circularity of energy systems, low carbon mobility, and strengthened carbon sinks which lead to lesser pollution and carbon emissions in the city. Turku also aims to become climate-positive with negative net emissions. The marine area contaminated with phosphorus and nitrogen is also managed by wastewater plants. Similarly, Chemistry Park was established to recycle industrial waste into high-value chemical products.

Least polluted cities in world- Sheet10
Turku, Finland_©istock

10. Funchal, Portugal (4.51 µg/m3) | Least polluted cities in worldv

Funchal is fortunate to be located on an island amidst the Atlantic Ocean and far away from the mainlands of Europe and Africa. However, the authorities had placed sustainability and environmental protection at the heart of their concerns. It comes closest to the ideal green space for the city. It is this integration between an urban and natural landscape that is the key to creating a sustainable and livable environment that as a result will also produce a clean atmosphere.

Least polluted cities in world
Funchal, Portugal_©Jurga


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  2. Veal, L., 2020. How Iceland is undoing carbon emissions for good. [online] Available at: <>
  3. 2021. The Ocean Conference | Iceland commits to reduce marine litter in its waters. [online] Available at: <> 
  4. O&#039;Donnell, S., Fontaine, A., Grapevine, T., Grapevine, T., Huhta, R., Huhta, R. and Huhta, R., 2019. From Iceland — Heavy Air Pollution In Reykjavík. [online] The Reykjavik Grapevine. Available at: <>
  5. Johnston, F., Hanigan, I., Henderson, S., and Morgan, G., 2013. Evaluation of interventions to reduce air pollution from biomass smoke on mortality in Launceston, Australia: retrospective analysis of daily mortality, 1994-2007.
  6. editor, L., 2021. Smoke pollution risks persist in Launceston. [online] The Examiner. Available at: <> 
  7. D. Lamontagne, N., 2021. Finding Out Why a Seemingly Low-Emissions City Has So Much Smog. [online] Thriving Earth Exchange. Available at: <> 
  8. Ketchell, M., 2020. From Hobart to London, to Dhaka: using cameras and AI to build an automatic litter detection system. [online] The Conversation. Available at: <> 

Guruprasath believes in a conscious approach towards architecture, which fulfills the intentions of the people towards the built spaces and vice-versa. He is more interested in understanding architecture, which made him incline towards writing on architecture. He also enjoys reading and writing other stuff.