Survey names Lahore, Pakistan, most polluted city on earth

The Pakistani city of Lahore rose 10 ranks from 2021 to become the city with the worst air quality last year, while Bangladesh was replaced by Chad as the world's most polluted country, a report published by the Swiss firm IQAir found on Tuesday.

In 2021, air quality guidelines released by the World Health Organization (WHO) recommended an annual PM2.5 exposure concentration of not more than 5 micrograms per cubic meter. 

PM2.5 is a major air pollutant that is used for examining air quality and is measured in micrograms per cubic meter.

What is PM2.5 concentration?

This is the amount of a certain type of particles present in the air that are up to 2.5 microns in size. 

Combustion engines, industries, wood burning, construction and agricultural processes can produce these particles, which can vary chemically and in size.

The PM2.5 particles have a negative impact on human health. This is due to the fact that the human nose can filter out larger particles but smaller and ultrafine particles can get inhaled into the lungs where they can either enter the bloodstream or deposit within the lung lining.

What were the city-based results?

Lahore's air pollution rose to PM2.5 levels of 97.4 micrograms per cubic meter from 86.5 in 2021, replacing Bhiwadi in Indiaas the most polluted city globally.

Bhiwadi and Delhi were next in the rankings, ,with pollution levels reaching up to 92.7 and 92.6 respectively.

Indian cities filled 12 of the to 15 rankings of the most polluted cities in the world, the same as in last year's report.

and Pakistan had India in the South Asia region, as well. Nearly 60% of the population in Central and South Asia live with PM2.5 levels that are seven times more than what the WHO guidelines have recommended.

According to a World Bank pollution report on South Asia for the year 2022, nearly two million people died due to air pollution across the region.

What were the country-based results?

The central African nation of Chad was ranked the most polluted country in the world, with a 12 percent increase in annual PM2.5 concentrations from 2021. According to the report, this was mainly due to the burning of grasslands.

Around 70% of global wildfires occur in Africa, NASA satellite data suggests.

Iraq ranked as the second most polluted country with the pollution in the West Asia region being attributed to the rising dust storms.

Pakistan ranked third, followed by Bahrain as the fourth most polluted country.

Bangladesh improved its air quality ranking to the fifth position. Last year it was labeled as the most polluted country in the world with PM2.5 concentrations of 76.9. These now have come down to 65.8.

Also, China, Taiwan, South Korea, and Mongolia were able to improve their air quality while for Japan the levels remained the same as in 2021.

Air quality also improved in the United States, with nine out of the ten most populated cities in the US has reduced PM2.5 levels in 2022 in comparison with 2021 levels.

Australia's Canberra had the cleanest air amongst the world's capitals.

Fifteen countries in Europe had reduced air quality levels than in 2021.

How were pollution levels measured?

IQAir collected data for PM2.5 concentrations from more than 30,000 air monitoring stations located in more than 7,300 spots in 131 countries and regions.

The data was then analyzed keeping certain factors in check, such as the country's population.