The capitals of India and Bangladesh see thick layers of toxic smog, ‘very poor’ air quality and normal lives.

Dhaka briefly emerged as the world’s most polluted city on Wednesday, with a “hazardous” index level of 325, according to Swiss climate monitor IQAir.

By midday, however, conditions improved slightly, with the index dropping to 177 – still in the “unhealthy” range.

The air quality in Dhaka, one of the world’s most crowded cities with more than 20 million residents, has worsened in recent years as fossil fuels are overused, bringing health problems for the people.

“We often suffer from asthma, fever and allergies while operating rickshaws on the streets,” said Rafiq Mondal, who drives a vehicle for a living. “It is often very painful.”

While authorities in Dhaka spray the streets with water to help the dust settle, residents want additional steps taken.

“The air pollution is taking its toll,” said resident Wasim Akhter.

“With all the mega projects like the metro rail overhead, there is a lot of construction material everywhere … Measures must be taken more seriously.”

The World Bank has urged Bangladesh to coordinate more closely with its South Asian neighbours to clean up the air.

Air pollution, which is often a mix of solid particles, liquid droplets and gasses,  accounts for one-fifth of deaths in the country each year, it said in a report.

In New Delhi, which often leads the world’s most polluted list, the AQI index on Wednesday read 378, according to the Central Pollution Control Board – a rating of “very poor”.

The dense fog in the Indian capital and across northern India led to the delays of more than 100 flights and the disruption of rail services as visibility reduced to barely 50 metres (164 feet) in some areas.

Dense fog contains particulate matter and other pollutants, according to the weather department, which warned of the impact this may have on the health of the city’s tens of millions of residents.

Other parts of north India, including the states of Punjab, Uttar Pradesh and Haryana reported similar weather conditions.