Pollutants dispersing in Delhi but air quality still bad

21 Oct 2017

The volume of pollutants markedly came down in Delhi today with their rapid dispersion caused by a strong wind movement, a day after Diwali fireworks pushed the city's air quality into the 'severe' zone for the first time this year.

The Central Pollution Control Board (CPCB), which attributed Friday's high pollution levels to calm wind movement and a low mixing height (where air and suspended particles mix), said the situation will improve further by Sunday if favourable conditions prevail. "The wind speed is expected to pick up and reach up to 9 km/hour, which is adequate enough for the dispersion of suspended particulates. Yesterday and the day before, wind speed and mixing height were extremely low, which led to the rapid build-up of pollutants near the surface," Dipankar Saha, CPCB's air lab head, told news agency PTI.

The improvement was captured by the pollution monitoring stations. Six out of the eight stations maintained by SAFAR (System of Air Quality Forecasting and Research), an agency under the Ministry of Earth Sciences, had air quality index (AQI) in the 'very poor' category, a shade better than 'severe'. Among the station maintained by the CPCB, nine out of 17 were in the 'very poor' category, while the rest recorded 'severe' air quality.
A 'very poor' AQI comes with the warning that people may develop respiratory illness on prolonged exposure while exposure to 'severe' air affects healthy people and seriously impacts those with existing respiratory or cardiovascular diseases. At 12 pm, the 24-hour rolling average of PM2.5 and PM10, ultra-fine particulates, which are up to 30 times tinier than the width of a human hair, were 206 and 357 microgrammes per cubic metre (ug/m3) respectively, as against yesterday's 407 and 595.

Their 24-hour safe standards are 60 and 100 and anything beyond that is considered harmful as these particles enter the respiratory system and can manage to reach the bloodstream, causing irreparable damage to humans and animals.