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Friday, November 27, 2020

Capital reels under worst air quality so far

The overall air quality continued to remain in the ‘severe’ category —- which impacts healthy people and also those with existing medical conditions — throughout the day until at least 7 pm.

By: Express News Service | New Delhi | Updated: November 6, 2020 8:56:16 am
Delhi pollution, Delhi AQI, Delhi air quality, Delhi air pollution, delhi city newsDelhi’s 24-hour average air quality index on Thursday was 450, the highest it has reached this season. (Express photo: Abhinav Saha)

Bursting of firecrackers, higher vehicular pollution due to festivities and the season’s highest increase in farm fires, together with poor weather conditions, pushed Delhi’s air quality into the ‘severe’ category on Thursday.

The overall air quality continued to remain in the ‘severe’ category —- which impacts healthy people and also those with existing medical conditions — throughout the day until at least 7 pm.

PM2.5 particles emitted from farm fires in Punjab, Haryana, Uttar Pradesh and Uttarakhand had an estimated 42% share in Delhi’s air pollution on Thursday, the highest it has reached in the season this year, as per the Centre’s System of Air Quality and Weather Forecasting and Research (SAFAR).

Dr V K Soni, head of the India Meteorological Department’s Environment Monitoring and Research Center, said, “After 10 am on Wednesday, the wind speed deteriorated and became very slow. Along with this, the number of fire counts increased significantly — it was around 5,000 on Wednesday, which is the season’s highest count.”

Dr Soni added, “The deterioration in air quality was a combination of emissions from farm fires and slow wind speed, in addition to local emissions, such as fireworks that were noted on Wednesday and higher vehicular pollution due to festivities.”

Delhi’s 24-hour average air quality index (AQI) on Thursday was 450, the highest it has reached this season, as per data from the Central Pollution Control Board (CPCB). On Wednesday the AQI was 343. with the air quality in neighbouring NCR towns also hovering in the ‘severe’ category.

Reduction of mixing depth — height available in atmosphere for pollutants to disperse — lowered to around 500 metres on Wednesday due to calm winds and low temperature, as per a SAFAR bulletin.

“This led to the trapping of (farm) fire-related and local pollutants to a layer very close to the surface. Not-so-calm surface winds are forecast for the next two days, favouring dispersion of pollutants slowly. AQI is likely to improve to the lower end of ‘severe’ to higher end of ‘very poor’ category for the next two days,” the SAFAR bulletin said.

However, as winds are from the northwest direction, which favours transport of emissions from farm fires, the improvement in AQI could not be as expected if more fires are recorded, the bulletin added.

The concentration of PM10 and PM2.5 — fine particles suspended in the air — breached the ‘severe +’ or ‘emergency’ levels of 500 µg/m3 and 300 µg/m3 after midnight on Thursday in Delhi-NCR, against their 24-hour exposure limit of 100 µg/m3 and 60 µg/m3. As of 5pm on Thursday, the level of PM10 was 487 µg/m3 and of PM2.5 was 305 µg/m3.

SAFAR’s health advisory when the AQI hits ‘severe’ range is to avoid all physical activity, close windows, avoid burning candles, wood or even incense, and frequently using a wet mop to clean the room. It advises people to stop any activity that causes unusual coughing, chest discomfort and breathing difficulty.

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