delhi

Updated: Dec 11, 2016 12:42 IST

Air quality in the national capital stayed “very poor” on Sunday as dense fog descended on the city in the early hours even as the Regional Weather Forecasting Centre (RWFC) said it expects fog to subside from Sunday.

The overall Air Quality Index read 369, which is “very poor”. Individual air quality monitoring stations had AQI readings between 300-400, with Dhirpur clocking the highest reading at 398.

According to the System of Air Quality Weather Forecasting and Research (SAFAR) advisory, people with heart or lung diseases must avoid exertion when the air quality is “very poor”.

In the morning, the 24-hour rolling average of PM10 and PM2.5 touched very poor limits, respectively, according to (SAFAR) data, reading 343 and 210 microgram per cubic metre, respectively.

PM2.5 and PM10 are ultra-fine particles that are the dominant pollutants in Delhi. The acceptable levels of PM 2.5 and PM10 are 60 and 100 microgram per cubic metre respectively.

Forecasts had predicted this foul air quality because of cold waves in the entire northern belt, upper wind towards Delhi region and calm lower winds.

The main factors that influence Delhi’s air quality are wind speed and direction. Whenever the surface wind speed decreases, pollution levels shoot up.

Delhi, a city of about 20 million people, is among the world’s most polluted according to the World Health Organisation, has been struggling to clean up a toxic cocktail of dust, smoke and gases from its air.

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WHAT’S CLOUDING DELHI THESE DAYS? Winter has just set in. But a series of foggy days in the Capital make it seem like it is alrea dy peak winter. Experts attribute it to the five-year-low average wind speed.



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