Instead, Delhi’s air quality in January-June was far better compared to the year-ago period, the environment minister said.

Environmentalists cautioned that it was early days yet and the government would have to step up efforts to control pollution with the winter approaching in a few months.

In December 2016, the Supreme Court had approved GRAP to tackle air pollution in Delhi and adjoining regions. The plan’s main objective was to institutionalize measures to tackle air pollution emergencies in the city, giving a clear direction about steps to be taken by central and state authorities.

GRAP was then notified by the union environment ministry in January 2017. It classifies air pollution into four categories of air quality—moderate to poor, very poor, severe, very severe or emergency.

Moderate to poor is the air quality when particulate matter (PM) 2.5 and PM10 levels are between 61-90 µg/m3 (microgram per cubic meter) and 101-250 µg/m3 respectively; very poor is when PM 2.5 or PM 10 levels are between 121-250µg/m3 and 351-430 µg/m3 respectively; severe is when ambient PM 2.5 or PM 10 levels are more than 250µg/m3 and 430µg/m3 respectively and very severe or emergency is when PM 2.5 or PM 10 levels are above 300µg/m3 and 500µg/m3 respectively, and persist for 48 hours or more.

“Since the launch of Graded Response Action Plan, there has not been a single day with severe level of air pollution. As far as other levels of air pollution are concerned such as very poor, poor or moderate, the government has taken a number of measures for controlling air pollution in addition to Graded Response Action Plan,” Harsh Vardhan said in reply to a query in Rajya Sabha on Monday.

Explaining further, the environment minister said that the data available for the last three years shows that “exceedance is mainly observed with respect to particulate matter, though the analysis of time series data relating to particulate matter does not show any significant rising trend during last three years despite rise in population, number of vehicles and other economic activities.”

“The Air Quality Index (AQI) data of Delhi for the period of January-June for 2016 and 2017 shows that there were no days with severe level of air pollution in 2017, whereas there were seven days with severe level of pollution during 2016,” said Harsh Vardhan.

Similarly, the minister added that the data also highlights that days of moderate pollution have gone up from 29 days in 2016 to 56 days in 2017”.

“Very poor days have reduced from 64 in 2016 to 36 during 2017. The above data shows improvement in air quality in Delhi in 2017 for the first six months in comparison to 2016,” he added.

The Central Pollution Control Board (CPCB) and the State Pollution Control Boards (SPCBs) monitor ambient air quality in the country under the National Air Quality Monitoring Programme (NAMP). Three air pollutants—sulphur dioxide (SO2), nitrogen dioxide (NO2) and particulate matter (PM10)—are monitored at 684 manual monitoring stations in 302 cities/towns in 29 states and five union territories, out of which 10 are in Delhi.

“After the horrible smog that Delhi saw after Diwali, the plan for a graded plan was catalysed. This improvement that we are seeing ...gives confidence that it is possible to arrest rising pollution but it is too early to say whether this decline is a trend or not,” said Anumita Roychowdhury, executive director at the Delhi-based Centre for Science and Environment (CSE), a non-governmental organization working on health and environmental issues.

“For this decline to continue, we have to ensure that action is now stepped up even more as we are going to face winter soon. Our preparedness needs to be much stronger so that we can truly bend the pollution curve,” she added.