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Delhi’s air in November, December 2017 cleaner than 2016: CPCB

In this period in 2016, there were 11 days with Air Quality Index (AQI) at ‘severe’ level while there were seven days with this level in 2017.

delhi Updated: Dec 10, 2017 00:40 IST
Ritam Halder
Ritam Halder
Hindustan Times
delhi,delhi news,pollution
This year also witnessed the lone ‘moderate’ day in terms of air quality in this period and experts say this is because of the control on local emissions in the city.(Burhaan Kinu/HT PHOTO)

The air quality in the months of November and December 2017, till date, is cleaner compared to the corresponding months of 2016, the Central Pollution Control Board (CPCB) data has revealed.

In this period in 2016, there were 11 days with Air Quality Index (AQI) at ‘severe’ level while there were seven days with this level in 2017.

The AQI calculated on a scale of 0-500. An AQI between 0-50 is considered good, 51-100 satisfactory, 101-200 moderate, 201-300 poor, 301-400 very poor and 401-500 severe.

This year also witnessed the lone ‘moderate’ day in terms of air quality in this period and experts say this is because of the control on local emissions in the city.

“On December 7, we had the best air quality in winters, since the launch of our national air quality system. On that day, average PM10 was 170 and PM2.5 was 100. Considering 35% non-reactive crustal materials in PM10 and same in PM2.5 about 30% (natural dust), the estimated concentration values for PM10 and PM2.5 will be 110 and 70 microgram per cubic metre (μg/m3) respectively. And this is because of some control on local emission sources this year,” CPCB air laboratory chief Dipankar Saha told Hindustan Times.

Both PM10 and PM2.5 are ultra fine particles that are the dominant pollutants in Delhi. The acceptable levels of PM10, the larger particulate matter, and PM 2.5, which measures the finer and more dangerous particulate matter, are 100μg/m3 and 60μg/m3 respectively. The PM2.5 particulates, which can measure up to 30 times tinier than the width of a human hair can reach the bloodstream of a person through the respiratory system and pose serious health risks.

This year too, Delhi witnessed one of the worst smog episodes in recent times. In the week following November 7, the AQI remained in ‘severe’ levels. A dust storm from the Gulf area, and stubble burning in Punjab and Haryana were the main reasons behind the thick layer of smog that had engulfed Delhi and adjoining areas.

As the Supreme Court-mandated graded response action plan (GRAP) is in force this year, during this period, measures under ‘severe plus’ or emergency levels like shutting of construction sites and entry of trucks in the city were announced. As the air quality improved, stricter measures were rolled back but many like shutting down the Badarpur power plant, ban on diesel generator sets, closure of brick kilns, hot mix plants and stone crushers, among others, are still in place.

“In normal conditions, 70% of the total pollutants are emitted due to the ground level activities. If we follow the preventive measures, we can bring it down as demonstrated this winter by means of inspection, cross verification, adoption of stricter measures, fixing the accountability, entrusting responsibility and regular review. Next year, we will be better prepared,” Saha said.

Air turns ‘very poor’ again

On Saturday, however, the air quality became ‘very poor’ with the AQI touching 305. CPCB scientists said this was because of calm conditions during the day as the wind speed dropped substantially.

First Published: Dec 10, 2017 00:39 IST