In Delhi on Thursday, PM 10 concentration was 399 µg/m3 — almost five times that of Paris — but only one of the many measures that the capital’s Environment Pollution Control Authority had suggested is in place, the ban on diesel generators.

* Odd-even restriction in place.

* Public transportation made free.

* Health advisory for elderly and children issued.

* School children asked to not exercise outdoors.

On Thursday, Paris Mayor Anne Hidalgo met a delegation of pulmonologists from hospitals of the Ile-de-France to discuss the effects of high pollution levels over the last nine days.

“Immediate measures, including the introduction of vehicular restriction, were taken as pollution levels remain high for a very long duration in Paris,” said a statement issued by the mayor’s office.

Hidalgo later tweeted: “The #Alternatecirculation is not THE solution but 1 emergency measure that curbs the rise in particle levels #StopPollution #pollution.”

Air Paris, Paris’s air quality monitor, said the peak was due to the accumulation of pollutants because of anticyclonic conditions which result in a drop in wind speed and slow dispersion of pollutants.

A similar weather pattern caused a sharp dip in Delhi’s air quality for a week after Diwali in November.

This is the fourth time that the odd-even restriction was introduced in Paris to control air pollution since 1997, 2014 and 2015. According to news agencies, the restrictions are expected to remain in place till PM 10 levels fall below 80 µg/m3.

In Delhi, the odd-even restriction came into force for the first time in January this year after PM 10 levels cross 430 µg/m3. And, given the current levels of PM 10, the Supreme Court had mandated that parking fee be hiked 3-4 times, bus and metro frequency increased and the use of coal and firewood in hotels and open eateries stopped.

None of that has happened.

“The government is waiting for a detailed order from the Supreme Court. Once that happens, it will be notified and all governments concerned will have to follow the norms mentioned. We cannot delay the process. This is the time that is it needed the most as this is one of the most polluted months of the year and this is when action is needed the most,” said AnumitaRoychowdhury, executive director, Centre for Science and Environment.

“Many restrictions are already in place. The odd-even restriction takes a lot of effort to bring in. It is good that the Supreme Court has endorsed it,” said a senior Delhi government official.

According to air pollution experts in Delhi, the vast difference between air quality standards in India and cities in developed countries is because of the way pollution sources are managed.

“Our standards are still at an intermediate level as pollution is still very high. Each country’s aim is, ideally, to meet the World Health Organisation standards. Standardisation for every country is, thus, a dynamic process. Other countries have worked to improve emission levels from all sources of pollution, be it power plants, industry or vehicles. In 1952, during the

London Smog incident, their pollutant levels were worse than ours but they worked holistically to improve things,” said Roychowdhury.