Union environment minister Prakash Javadekar on Saturday accused Delhi chief minister Arvind Kejriwal of “politicising” the National Capital Region’s problem of air pollution, referring to his encouragement to schoolchildren to write to the Punjab and Haryana chief ministers.

“It is unfortunate that Delhi CM Arvind Kejriwal is politicising the issue of air pollution and instigating students to write a letter to Haryana and Punjab CMs to show them in bad light and present them as villains,” Javadekar tweeted.

Punjab has a Congress chief minister while Haryana has one from the BJP.

Air pollution over the NCR remained in the highest hazard category on Saturday with concentrations of the tiny particulate matter (PM) sized 2.5 microns and 10 microns reaching four times the safe limits.

Kejriwal had on Friday told schoolchildren in Delhi that smoke from the burning of crop stubble in Haryana and Punjab was causing the pollution, and asked them to write to the two states’ chief ministers urging them to control the practice.

“Please write letters to Captain (Amarinder Singh) uncle and (Manoharlal) Khattar uncle and say: ‘Please think about our health’,” Kejriwal had told children at a school after distributing facemasks among them, a PTI report said.

The Delhi government has procured five million facemasks for distribution among children at public and private schools, the report said.

Javadekar said in his Twitter posts that the problem of air pollution had got aggravated over the past 15 years and was “now being effectively remedied” by the Narendra Modi government.

“We have started inter-state meetings of NCR ministers and officials. All stakeholders need to act together and not blame each other,” Javadekar said.

“I appeal to all agencies to work together in combating air pollution and give relief to people and not indulge in cheap politics.”

Data available with a central government agency that tracks the air quality over the NCR indicate that stubble burning contributed significantly to the air pollution on October 31 and November 1.

“The stubble share in Delhi’s PM2.5 touched a season’s high of 44 per cent on October 31 and 38 per cent on November 1,” the agency, System for Air Quality Forecasting and Weather Research (Safar), which functions under the earth sciences ministry, said.

The contribution of stubble burning to PM2.5 over Delhi was expected to fall to 17 per cent on Saturday as a result of changes in the wind direction and a fall in the number of stubble fires, Safar said.

Javadekar said the Modi government had helped nearly 3,000 industries shift to piped natural gas, an alternative to the polluting fossil fuels, and nearly 3,000 brick kilns to adopt cleaner technology.

He added that the Modi government had completed expressways that allowed nearly 60,000 heavy trucks to bypass the capital, and had “fast-paced” the Metro’s development to encourage public transport.

Javadekar underlined that the Delhi government “did not give their share” towards these initiatives and that a court had to intervene for the payments.

Strong winds are expected to disperse some of the accumulated pollutants and push the air quality from the current “severe” to the “very poor” category by November 4, Safar said.