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Air Quality Deterioration

From smog hanging over cities to smoke inside the home, air pollution poses a major threat to health and climate. The combined effects of ambient (outdoor) and household air pollution cause about 8 million premature deaths every year, largely as a result of increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections. More than 80% of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed the WHO guideline level of 10µg/m3, with low and middle-income countries suffering from the highest exposures. When it comes to human health, clean air is the most basic amenity. Sadly, today, inadequate air quality is one of the major causes of a variety of acute health issues.

The air quality index (AQI) is a metric for reporting air quality on a daily basis, with the objective of informing people about how the local air quality impacts their health. The Environmental Protection Agency (EPA) calculates the AQI for six common air pollutants (also called "criteria air pollutants"), for which national air quality standards have been established to safeguard public health.

  1. Ground-level ozone
  2. Particle pollution/particulate matter (PM2.5/PM 10)
  3. Lead
  4. Carbon Monoxide
  5. Sulfur dioxide
  6. Nitrogen dioxide

The higher the AQI value, the greater the level of air pollution and more serious the health concerns.

The world's most polluted cities
City Country AQI
Winnipeg Canada 201
Toronto Canada 176
Ahvaz Iran 167
Mississauga Canada 164
Durban South Africa 156.5
Vahdat Tajikistan 155
Puebla Maxico 155
Manama Bahrain 139
Sitrah Bahrain 139
Jakarta Indonesia 136.5
The world's least polluted cities
City Country AQI
Almaty Kazakhstan 2
Bandar Seri Begawan Brunei 6
Villach Austria 6
Canberra Australia 8
Calgary Canada 9
St. Gallen Switzerland 9
Salzburg Austria 10
Ecatepec de Morelos Maxico 11
Cluj-Napoca Romania 11
Adelaide Australia 12

Source: AQICN, Harvard, EPA
Updated On: 14 Jul, 2025

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