The air quality in Delhi improved marginally on Tuesday, showed real-time data by the System of Air Quality and Weather Forecasting and Research, or Safar. On Monday, the air quality was in the “severe” category while on Tuesday it was in the “very poor” category.

At 3 pm on Tuesday, Safar recorded the air quality index at 379 in Delhi. According to the Central Pollution Control Board, any reading of the air quality index or AQI above 100 on a scale of 500 is progressively unsafe for health.

Levels of the most dangerous particles, PM2.5, was 223 micrograms per cubic meter on Tuesday.

“Today’s share of crop residue burning is 30 per cent in PM2.5,” Safar said, according to ANI. “AQI is likely to improve further but remains in very poor category.”

Particulate matter smaller than 2.5 microns (or about a ten-thousandth of an inch) is particularly dangerous to human health. Such particles are small enough to travel deep into the respiratory system, potentially impairing lung function.

Air pollution in Delhi typically worsens in October and November due to farmers burning stubble in neighbouring states, unfavourable wind speed and emission of fumes by the local traffic in the city. Firecrackers ignited for Diwali add to the problem.

The Central Pollution Control Board on Monday issued a notification, suggesting measures to curb the worsening air quality in Delhi, the Hindustan Times reported. The board recommended mechanically cleaning roads, sprinkling water on the streets and shutting of brick kilns in the region.

“Intensify public transport services,” the Central Pollution Control Board said. “Introduce differential rates to encourage off-peak travel. States to disseminate information about air pollution levels and for creating awareness among citizens regarding steps to minimise air pollution.”

Meanwhile, the North Delhi Municipal Corporation has stopped construction and demolition activities at 54 private sites for violating environment norms, an unidentified official said, according to PTI. People who were violating the environment pollution guidelines were fined Rs 16 lakh.