Dhaka third among megacities with worst air pollution, better than Delhi: WHO

World Health Organization has ranked Dhaka third worst among megacities with polluted air in a report on air quality in 792 cities of 67 countries.

According to the report published on Tuesday, the annual average presence of particulate matters with a diameter of 10 micrometres or PM10 per cubic metre in the capital of Bangladesh was 104 micrograms in 2016, 145 micrograms in 2015 and 150 micrograms in 2014.

The data focused on PM10 and particles with a diameter of less than 2.5 micrometres or PM2.5.

PM2.5 includes toxins such as sulphate and black carbon, which pose the greatest health risks as they can penetrate deep into the lungs or cardiovascular system.

They can cause diseases such as strokes, heart disease, lung cancer and respiratory infections such as pneumonia, WHO said.

The level of PM2.5 in Dhaka was 57 micrograms in 2016, 82 micrograms in 2015 and 85 micrograms in 2014.

According to WHO standards, up to 20 micrograms PM10 and 10 micrograms PM2.5 per cubic metre air can be called healthy.

The UN organisation ranked 11 megacities with a population of over 14 million each based on the air pollution data from 2011 to 2015.

Delhi topped the list with Cairo coming in second worst.

WHO says more than 80 percent of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed the WHO limits.

While all regions of the world are affected, populations in low-income cities are the most impacted, it says.

According to the latest air quality database, 97 percent of cities in low- and middle income countries with more than 100,000 inhabitants do not meet WHO air quality guidelines.

However, in high-income countries, that percentage decreases to 49 percent.

As urban air quality declines, the risk of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases, including asthma, increases for the people who live in them, the organisation says.

The condition of Narayanganj city is worse than megacity Dhaka. The city on the bank of the Shitalakkhya river had 94 micrograms PM2.5 and 205 micrograms PM10 in 2015.

According to the 2015 data, the levels of particulate matters in seven cities of Bangladesh – Dhaka, Chattogram, Gazipur, Barishal, Khulna, Narayanganj, and Sylhet – exceeded the WHO limits.

According to the WHO report, 13 of the worst 20 cities by air pollution are in India. Besides Delhi, the air in Mumbai, Pune and Kolkata is also highly polluted.