The air quality in Delhi on Tuesday slipped to “severe” category, according to the Central Pollution Control Board data.

At 10 am, the national capital’s Air Quality Index, or AQI, stood at 429. An air quality index ranging between 401 and 500 falls under the “severe” category. A reading of above 400 can affect healthy people and seriously impact those with existing illnesses.

Levels of the PM2.5 fine particles was 247 micrograms per cubic meter on Tuesday morning, showed real-time figures from the Ministry of Earth Sciences’ SAFAR, or System of Air Quality and Weather Forecasting And Research.

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

To be considered safe, the National Ambient Air Quality Standards require PM2.5 concentration in air to be less than 60 micrograms per cubic metre in any given 24-hour period.

The air quality in Delhi is likely to remain between “severe” to “very poor” category for the next six days, according to the Central government’s Air Quality Early Warning System.

Larsen & Toubro fined

Delhi Environment Minister Gopal Rai on Tuesday said that construction firm Larsen and Toubro has been fined Rs 5 lakh for violating the ban on construction and demolition work. “Workers said that the construction may have been related to the BJP’s headquarters,” he said. “We are finding out the details.”

Rai alleged that stone-cutting work was being carried out at the site, and that soil was lying in the open there.

The Delhi government minister alleged that the ideology of the Bharatiya Janata Party favours rising air pollution levels, according to PTI.

“Punjab would have seen a large-scale reduction in stubble burning had the Centre supported the state government’s initiative to provide a cash incentive to farmers for not burning crop residue,” he added.

Rai also said that BJP leaders supported the burning of firecrackers during Diwali. “They too live in Delhi,” he said. “All of us should work together to fight air pollution.”

The Aam Aadmi Party government in Delhi had announced on Sunday that it has formed 586 teams to ensure strict implementation of the ban on construction and demolition activities to prevent the air quality from deteriorating.

The Commission for Air Quality Management has directed authorities in the National Capital Region to immediately implement restrictions under stage three of the Graded Response Plan Action – a step-by-step emergency measures to fight the pollution.

Air quality deteriorates sharply in the winter months in Delhi, which is often ranked the world’s most polluted capital. Stubble burning in Punjab and Haryana, along with falling temperatures, decreased wind speed and emissions from industries and coal-fired plants contribute to air pollution.

On Tuesday, satellite images from the National Aeronautics and Space Administration, or NASA, showed a dense cluster of red dots – signifying farm fires – in Punjab and parts of Haryana, according to PTI.

The Indian Agricultural Research Institute said that there were 2,131 farm fires in Punjab on Monday, the highest so far in this season.