– Thick toxic smog enveloped New Delhi for a second straight day on Wednesday, forcing schools to shut down, halting traffic on highways and sending residents scurrying to buy air purifiers and filtration masks.

Chief Minister Arvind Kejriwal, the leader of Delhi, a megacity of around 20 million people, called the capital a “gas chamber” as his government sought meetings with adjoining states to address the issue.

By midafternoon, the deadly level of carcinogenic pollutants in New Delhi’s air was roughly 10 times the reading in Beijing, a city more globally infamous for its air pollution. Experts are calling the situation in New Delhi a major public health emergency.

The crisis was “the worst that I have seen in my 35 years staying in the city of Delhi,” said Arvind Kumar, a lung surgeon at Sir Ganga Ram Hospital. “The situation today is a public health emergency. If you want to protect people, we should be ordering the evacuation of Delhi.”

Shikha Gupta, 32, an IT professional in Delhi, has kept her children and elderly parents inside and has stopped taking her morning walks. “I just stepped out of my office a couple of minutes ago and my eyes are burning already,” she said.

The levels of the deadliest, tiny particulate matter — which lodge deep in a person’s lungs — soared overnight Wednesday to 726, according to a U.S. embassy monitor.

World Health Organization guidelines suggest exposure to levels of about 10, while anything less than 50 is considered healthy and levels above 300 are considered “hazardous.” Wednesday afternoon, Beijing had a level of around 76 while pollutants in Delhi’s air measured 833.

The organizers of an international half-marathon scheduled Nov. 19 said they are constantly monitoring the situation but have decided to hold the race. To minimize the impact of pollution, the organizers will wash the entire course with effluent water mixed with salt.

India’s Supreme Court last month banned the sale of fireworks ahead of Diwali, the Hindu festival of lights, in an attempt to reduce pollution.

Jai Dhar Gupta, who sells a pollution-filtering brand of facemasks in India, is dealing with a sudden deluge of orders. He said demand shot up 3,000 percent starting Sunday as the pollution began to worsen.

“The sad part is that people don’t take the polluted air threat seriously until they ‘see’ it,” he said.

Kejriwal blamed farmers in neighboring states for burning crop residue — an annual tradition to clear fields that combines with vehicle and industrial emissions — as well as road and construction dust for Delhi’s pollution.

A day earlier, a senior member of Prime Minister Narendra Modi’s Bharatiya Janata Party blamed the pollution on Kejriwal’s “failure to maintain” working relationships with nearby chief ministers — one of whom belongs to the ruling Bharatiya Janata Party.

Anumita Roychowdhury, executive director of research at advocacy group Centre for Science and Environment, said this year has seen fewer polluted days than last year. She blamed westerly winds for bringing crop smoke, while easterly winds reduced temperature and trapped fumes.

Last year, NASA satellite imagery showed thick plumes of smoke rising across north India and covering Delhi — similar to when the agency tracked fires from Indonesia’s Sumatra, which regularly drift over and pollute Singapore.

“During winters, the pollution problem is always atmosphere driven,” Roychowdhury said. “The important thing now is what can be immediately done.”