The odd-even plan will be implemented in the national capital territory from November 13 to November 20 to curb air pollution, Delhi’s Environment Minister Gopal Rai said on Monday as air quality remained in the “severe” category for the fifth consecutive day despite mitigation efforts.

The rule, which allows vehicles with odd-numbered licence plates on the road on dates with odd numbers and those with even-numbered plates on others, will be enforced a day after Diwali. “After studying the situation following the implementation, a decision will be taken on future actions,” he added.

Rai said that the decision was taken considering the likelihood that pollution levels will rise after the festival, during which firecrackers, even though banned, are often set on fire.

Air quality plunges 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, low wind speed and emissions from industries and coal-fired plants contribute to air pollution in the region.

At 3 pm on Monday, Delhi’s air quality index stood at 411, according to real-time figures from the Ministry of Earth Sciences’ SAFAR, or System of Air Quality and Weather Forecasting And Research.

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 261 micrograms per cubic meter. Particulate matter 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.

At a press conference on Monday, Rai said that all schools will be shut across the national capital till November 10. This is excluding students of Classes 10 and 12 preparing for board examinations.

On Sunday, the Commission for Air Quality Management put the Graded Response Action Plan, a set of anti-pollution measures, into effect at its highest level in Delhi and surrounding cities to tackle the crisis. This includes a ban on entry of trucks into Delhi, with some exceptions.

Further, light commercial vehicles registered outside Delhi will not be allowed to enter the city, with exceptions in place for vehicles that run on compressed natural gas, electricity or BS-VI diesel. A ban has also been imposed on construction and demolition activities related to linear projects such as roads, flyovers and pipelines.

On Sunday, Delhi-based think tank Centre for Science and Environment said in its report that the early start of the national capital’s smog episodes this year as compared to 2022 may be attributed to the low rainfall in September and October. At least three consecutive days of air quality index being in the “severe” category is considered one smog episode.

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