New Delhi: Delhi’s air quality level of ‘very poor’ on Diwali day was best in past three years but the air quality was far from satisfactory as it climbed to ‘severe’ level on Friday evening — a day after the Diwali celebrations.

However, what is certainly a reason to cheer is that the noise pollution on Diwali this year showed a declining trend compared to 2016.

“The sound level data on Deepawali day monitored during last four years reveals that in 2017 the sound level recorded is the lowest at all stations, even in humid atmospheric conditions," said an analysis revealed by the Central Pollution Control Board (CPCB), which is India’s nodal pollution watchdog.

According to CPCB, the air quality index (AQI) of Delhi on Diwali this year was recorded at 326 (very poor) compared to 426 (severe) in 2016 and 327 (very poor) in 2015.

“In spite of non-favourable meteorological conditions, the air quality on Deepawali this year has shown an improvement (compared to) last year, 2016. The air quality was not so good during previous two days of Deepawali, due to intrusion of humid air coupled with prevailing calm wind conditions," the CPCB analysis said.

But according to the System of Air Quality and Weather Forecasting and Research (SAFAR) of the Union ministry of earth sciences, the city’s air quality was ‘severe ‘on Friday evening and it is expected to remain the same on Saturday.

On Friday morning, the Particulate matter (PM)10 and PM2.5—the two deadliest components of air pollution— were at “poor" and “very poor" levels respectively. The level of PM10 was 256µg/m³ and PM2.5 was 154µg/m³—over two and half times the satisfactory levels.

By Friday evening, the PM10 level reached 595 µg/m³ (nearly six times the satisfactory limit) and PM2.5 was 407µg/m³ (over six times the satisfactory limit).

The satisfactory limit of PM10 is 100µg/m³ and PM2.5 is 60µg/m³. These fine particles can settle deep in the lungs and be absorbed in the bloodstream, which can lead to respiratory problems, cardiovascular diseases and lung cancer.

Disturbingly, PM10 and PM2.5 levels—during and after Diwali celebrations in some parts of the national capital—went as high as over 24 times and nearly 15 times, respectively, the satisfactory limit even this year.

Meanwhile, as per SAFAR, Delhi’s neighbourhood towns like Noida and Gurgaon too saw ‘severe’ air quality level.

While overall pollution level on Diwali was ‘very poor ‘ on the day of the festival, the data recorded by air quality stations of the Delhi Pollution Control Committee (DPCC) showed that levels of PM10 and PM2.5 touched scary levels during and after Diwali celebrations.

For instance, Anand Vihar, which is one of the most polluted areas of the national capital, recorded PM10 at 2,402 µg/m³ early Friday morning (over 24 times the satisfactory limit) and PM2.5 at 626 µg/m³ (over 10 times the satisfactory limit).

Similarly, RK Puram, which regularly witnesses high levels of pollution, recorded PM10 at 1180µg/m³ (nearly 12 times the satisfactory limit) and PM2.5 at 878µg/m³ (nearly 15 times the satisfactory limit) on Thursday night. On Friday, the area recorded PM2.5 at 925µg/m³, which was nearly 15 times the satisfactory limit.

However, 2017 is still better than last year, when a day after Diwali, city’s air quality was ‘severe’ and it resembled a gas chamber. Last year, the PM10 and PM2.5 levels were recorded at over eight times and ten times (respectively) the satisfactory limit.

The union environment ministry said AQI on Diwali and post-Diwali day was 426 and 425, respectively last year and it has been 326 and 367 this year.

“Air quality in Delhi has been better compared to last year. The number of ‘good’, ‘satisfactory’ and ‘moderate’ (air quality) days has increased and ‘poor’ and ‘very poor’ category has reduced significantly compared to 2016," said Union Minister of Environment, Forest and Climate Change Dr Harsh Vardhan in a statement on Friday evening.

“The year 2017 has seen positive changes with respect to air pollution in Delhi due to a number of steps taken by Union Government, State Governments and Government of Delhi," he added.

Anumita Roychowdhury, executive director, Centre for Science and Environment (CSE), a Delhi-based environment think tank, said, “Delhi and NCR have experienced this winter’s first ever emergency level on Diwali night. It is clear that the Delhi-NCR region requires a longer term and systemic action than a one-off ban."

“The Supreme Court has already ordered a phase down strategy with the help of regulation of chemicals, standards, reduced quantum of crackers, controlled bursting of crackers through community events, locational controls etc. This must be implemented without delay for a longer term solution to this problem," she said.

Roychowdhury said that their analysis has shown that despite the ban on sale of crackers by the Supreme Court, the air pollution levels breached the emergency standards on Diwali night.

“But it is also clear that without the ban on sale of firecrackers, the levels would have been far worse. Calmer wind and more moisture in the air on the post-Diwali morning worsened the pollution build-up on Friday," she added.

On 9 October, the Supreme Court had banned the sale of crackers in Delhi and NCR area.

Now whether the low pollution levels—compared to last year—are due to the apex court’s ban on cracker sale leading to less people bursting crackers, awareness among people, favourable weather conditions or the graded response action plan (GRAP), it is yet to be finalized.

After the alarming levels of pollution in Delhi-NCR area last year, SC had approved GRAP to tackle air pollution in Delhi and adjoining regions.

The main objective was to institutionalize measures to tackle air pollution emergencies, giving a clear direction of steps to be taken by central and state authorities.

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