Delhiites have been breathing easy this year, with the national capital at present witnessing its cleanest air in the last eight years.

In a city, which has been tagged as the most polluted in the world, the average air pollution level in the first seven months of the year have been the lowest, compared to the corresponding period of previous years since 2012, data provided by the Delhi Pollution Control Committee (DPCC) showed.

Even as experts attributed the drop in pollution levels to a series of anti-pollution measures initiated both by the Centre and the Delhi government, they cautioned that the levels of particulate matter (PM) in the city’s air was still around two to three times higher than the prescribed limits and pollution checking measures should be enforced stringently.

‘The levels of PM10 and PM2.5 – the two critical pollutants of Delhi – have been the lowest for the period of January to July when compared to previous years. This has been possible because of several measures that have been undertaken over the past two years at least,’ said MP George, a scientist with the DPCC.

While the average concentration of PM2.5, during the first seven months (January to July), has steadily dropped from 133ug/m3 in 2012 to 101ug/m3 in 2019, the level of PM10 has also come down from 326ug/m3 in 2012 to 237ug/m3 in 2019.

The daily and yearly prescribed limits of PM10 are 100ug/m3 and 60mg/m3 respectively. The daily and yearly prescribed limits of PM2.5 are 100ug/m3 and 60mg/m3.

According to the Central Pollution Control Board, the PM2.5 levels in Delhi dropped by 7.3% in 2018 when compared to 2017 and by 14.8% over 2016. Similarly reduction in PM10 levels in 2018 is 8.6% over 2017 and 16.5% over 2016.

‘In August, we have been experiencing ‘satisfactory’ air quality in the last ten days. The AQI has been staying between 55 and 70 over the past few days mainly because of meteorological conditions – rain and winds. The best air quality of this year so far was experienced on August 12, when the AQI dropped to 57,’ said a CPCB official.

On a scale of 0 – 500, an AQI value less than 50 is considered as ‘good’ quality air. At present Delhi is enjoying ‘satisfactory’ air quality. During winter months, the AQI shoots up to nearly 500, indicating severe levels of pollution and prompting authorities to shut down construction and industrial activities.

‘Pollution levels in Delhi-NCR depend primarily on ground-level human activities and meteorology. If we can check and control our ground level activities, much of the pollution can be brought down. Some measures have already been initiated and the results have started showing,’ said D Saha, former head of the CPCB’s air quality laboratory.

According to environment department officials in Delhi, the drop in pollution levels is the cumulative effect of a series of measures that have been undertaken over the past two years at least – introducing upgraded fuels such as BS-VI, CNG and PNG (for industries), shutting down of Badarpur power plant, implementing measures under GRAP, launching of eastern and western peripheral expressways, addressing pollution related complaints lodged by citizens on social media and banning fuels like coal and kerosene.

‘Even though pollution levels have dropped compared to previous years, the average air quality throughout the year is still not good because pollution is still two to three times above the prescribed limits. Just like we try to tackle our pollution sources during extreme events, we need to concentrate on the average air quality throughout the year by check sources. The number of good quality days need to be increased,’ Vivek Chattopadhyay, senior program manager (Clean Air Program) at the Centre for Science and Environment.

An earlier study by scientists from IIT-Delhi had revealed that over the past two decades almost, the average level of PM2.5 – pollutants that can penetrate deep inside the lungs – in Delhi has remained more than two times above the annual permissible limits.

According to CPCB data the number of ‘good’ to ‘moderate’ days had increased to 159 in 2018, as compared to 152 in 2017, and the number of ‘poor’ to ‘severe’ days had reduced to 206, compared to 213 in 2017.