Monday was the most polluted day after December 7, when air quality had first reached 'severe' level this month. According to data released by Central Pollution Control Board (CPCB), the highest average concentration of PM2.5 was 302.54 micrograms per cubic metre (g/m3) on Monday.

Air quality index (AQI) also peaked at 375 on Monday, compared to 190 on Sunday and 151 on Saturday. The value for PM2.5 prescribed by World Health Organisation (WHO) is 60g/m3. Thankfully, other pollutants, such as carbon monoxide, sulphur dioxide and oxides of nitrogen remained well below the prescribed values.

"Five days after December 7, AQI again reached 'severe' level on Monday. It was also more severe in the evenings, as that's when fog increases. Low temperatures and fall in wind speed are the main reasons behind it," said a Haryana State Pollution Control Board (HSPCB) official. While HSPCB held dip in temperature responsible for the rising pollution, experts put the blame on agricultural waste burning.

"Apart from diesel autos, I don't think the city has any other major source of pollution. Instead, the major pollution source has been stubble burning in and around the city. The PCB needs to adopt strict measures against farmers for the practice," said Deepak Chaudhary, professor of environmental sciences at Delhi University.

Niranjan Raje, a former member of the Environment Pollution (Prevention and Control) Authority, said, "Despite pollution levels going up on certain days, not many are talking about it as the days are relatively brighter. However, data shows things are indeed getting worse, with air pollution worsening as night approaches. The authorities should not wait for foggy days, but strictly implement anti-stubble burning norms to prevent a crisis."

"We are continuously inspecting fields and educating farmers about available alternatives to stubble burning. There are authorised companies that pick up the stubble, for example. Farmers just need to call their village's agricultural unit," he said.

Farmers, though, said these authorised dealers are inevitably late in arriving. "Last year too I had called the department to pick up stubble from my field. The authorised dealer arrived after 10 days. By that time, I had burnt it to be able to sow the next crop at the right time. I can't afford to wait for the company to pick up stubble and delay next season's produce in the process," Murid Lal, a farmer from Sultanpur, told TOI.

Weathermen predict the situation will remain the same for the next four days, and the situation may worsen thereafter. "It is going to be relatively foggier in the morning and evening on Tuesday and the Wednesday morning that follows. However, we will see bright sunny afternoons till Friday. With the temperature expected to fall below 9°C Saturday onwards, pollution levels are likely to remain high," said an official of the meteorological department.

Monday's minimum temperature was 12°C and maximum 25°C. The weather department forecasts temperatures to fall below 9°C Saturday onwards.