The measures, to be taken by Delhi, Rajasthan, Punjab, Haryana and Uttar Pradesh, include sprinkling of water by helicopters, shutting down of stone crushers and construction activities and transportation of construction material until air quality standards are brought below the severe level.

NGT noted that whenever particulate matter (PM) 10 and PM 2.5 are above the 431 g/m3 and 251 g/m3 mark, air quality is labelled as “severe”. This is the level at which even healthy people can develop respiratory problems and those with existing diseases are seriously impacted.

“Even if we give it a little bit of margin, once these values reach 500 and 300 respectively, it’s a case of environmental emergency. The states owe a Constitutional, statutory and public law obligation to provide to its citizens at least breathable if not absolutely clear air to breathe,” said the NGT bench headed by chairperson justice Swatanter Kumar.

The bench said if the situation reaches that level, all the states, and particularly Delhi, shall have to take emergency measures in addition to other preventive and controlling measures indicated in orders and judgments already passed by the apex court and the green tribunal.

The green tribunal’s order came just hours before the Supreme Court was scheduled to hear the central and state governments, which were asked to prepare a common and comprehensive plan to tackle air pollution. NGT pointed out that the Supreme Court had declared nearly a decade ago that Article 21 of the Constitution should be expanded to include clean environment as a fundamental right.

NGT’s order follows a slew of petitions filed after pollution reached hazardous levels in Delhi and the national capital region (NCR) after Diwali. Post-harvest stubble burning by farmers in the neighbouring states was partly blamed for the rise in pollution to 15 times of the safe limit.

The NGT passed a series of orders in 2014 and 2015 to control air pollution from vehicular emissions, waste burning, crop burning and construction dust but their implementation has been ineffective.

On poor air quality in Delhi for 10 days post Diwali, NGT’s bench remarked that, “it adversely affected public health and all generations without exceptions”

“The state owes a constitutional duty to protect public health and to provide at least clean air for its citizens to breathe. The children of today have a right to breathe clean air and play in playground rather than to be ordered to be shut down in homes. The present generation in any field, including in field of governance, owes a duty to provide cleaner and better earth to its next generation. Times have come when all concerned authorities irrespective of their stature must show concern to improve the ambient air quality in these states,” the,” the bench noted.

NGT also formed a committee headed by Union environment secretary that will include chief secretaries of the five states, member secretaries of the Central Pollution Control Board and State Pollution Control Boards and others.

This committee would have its first meeting on 17 November in Delhi and thereafter every two months in other state by rotation. It would supervise implementation of all anti-pollution orders of NGT passed in last two years particularly the one that is aimed at controlling agriculture residue burning.

Besides the central committee, the tribunal also ordered formation of five state-level committees who would meet every month. The state-level committees would be headed by chief secretary of the state and would include secretary environment, urban development and other important concerned departments. This committee would be responsible for implementing NGT’s orders at state level and the tribunal ordered for their first meetings on 24 November.

It also directed the Delhi government to ensure greenery on roads, under flyovers and around buildings.