Spotlight on air quality in Asian cities | Sunday Observer

Spotlight on air quality in Asian cities

Nov 6: As India’s north continues to struggle with extreme pollution levels, the story has put a fresh spotlight on air quality in cities across Asia.

Beijing has long been notorious for its smog - but statistics show that India, Pakistan and Bangladesh have worse air by far.

So why is South Asia so much more polluted?

Asia’s most polluted cities

Of the world’s most polluted 30 cities, 22 are in India, according to research by IQ AirVisual, a Swiss-based group that gathers air-quality data globally, and Greenpeace.

The remaining eight cities are all in Pakistan, Bangladesh and China - but the list doesn’t include Beijing, which comes in at number 122. Just looking at global capitals, it’s also Asian cities that top the ranking.

Looking at overall countries, it’s Bangladesh that has the worst air, followed by Pakistan and then India.

All these rankings are based on average air quality per year.

As these countries have very different densities of measuring stations and transparency of data, the statistics have to be read with a degree of caution. But they certainly indicate an overall trend.

World’s most polluted countries

Sorted by estimated average PM2.5

Source: World Air Quality Report

Why is India worse off than China?

Pollution in urban areas is usually a mix of different factors - mostly traffic, fossil fuel burning power plants and heavy industries.

What differentiates China from India is that in the latter, there is still a lot of burning of agricultural stubble when farmers want to clear their fields. The burning usually takes place in autumn. In the wake of the pollution spike, India’s Supreme Court ordered a stop to stubble burning in the states around Delhi. But the city’s situation is made worse by the colder winter air which is more stagnant, trapping the pollutants in place.

What does pollution feel like?

Pollution levels are categorised by measuring the levels of dangerous particles in the air. The result is then classified on a scale from good to hazardous. “The effect of pollution is different for every person,” explains Dr Christine Cowie of the University of New South Wales.

“Some people complain about irritation to the eyes, to the throat, exacerbations of wheeze and asthma symptoms. Coughing is certainly also a very common symptom - even in non-asthmatic people.

“And of course it’s the elderly who suffer, the very young and people with pre-existing respiratory illnesses like or heart problems.”

She explains that even a short exposure to the unhealthy or worse pollution levels can trigger an asthma attack or increase the risk of a stroke. The longer the exposure, the greater the risks. There’s the advice to stay indoors, to reduce physical exercise and to wear a mask - but in many poorer parts of the world, none of these options really work for regular people.

“It is toxic air,” says David Taylor, professor of tropical environmental change at the National University of Singapore.

“It must be very uncomfortable - especially if you’re having to work outside and if you’re having to do jobs that require quite a lot of energy.”

“You feel like it’s hard to breathe,” agrees Prof Smith. “It’s like doing hardcore exercise when you just take a walk outside. And depending on the kind of pollution, you can of course also smell it in the air.”