The Commission for Air Quality Management on Sunday directed authorities in the National Capital Region to immediately implement restrictions under stage III of the Graded Response Action Plan – a step-by-step emergency measure to fight pollution, PTI reported.

Under stage III of the plan, the restrictions include a ban on construction and demolition activities, except for essential projects concerning national security, defence, railways and metro rail, among others.

The development came after the national capital’s 24-hour average air quality index stood at 407 at 4 pm, according to PTI.

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 213 micrograms per cubic meter on Sunday evening, 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.