NEW DELHI — Pollution has once again soared to hazardous levels in Delhi, with a top expert warning that India's toxic air will have a bigger impact on public health than the Covid-19 pandemic.

On Wednesday, the air quality was 35 times over the safe limit set by the World Health Organization (WHO), leaving residents complaining of breathing problems, as well as itching in their eyes and throat.

Authorities have urged people, especially children and the elderly, to stay indoors as much as possible, while doctors recommend wearing a mask.

But Frank Hammes, global chief executive of air technology company IQAir, warns this is just a short-term measure - and much more needs to be done.

"Alarming air pollution levels are a public health pandemic," he told the BBC, explaining how toxic air impacts everything from mortality to IQ levels.

"This is going to have a much bigger impact on public health than Covid-19."

Every winter, Delhi and nearby states face high pollution due to low wind speeds, vehicle emissions and the burning of crop remains and firewood.

According to IQAir, a Swiss air quality index, pollution in parts of Delhi surpassed the 550 mark on Wednesday morning, far exceeding even the "hazardous" level of 300.

London, in comparison, had a level of 26 early on Wednesday.

The Air Quality Index (AQI) measures the level of tiny particles in the air, also known as PM 2.5 - which Mr Hammes explains is "the most dangerous pollutant" and the "only determinant" for calculating pollution levels.

"It causes breathing difficulties, asthma attacks, heart and lung issues that send people rushing to emergencies," he said.

The Delhi government reintroduced strict pollution control measures on Tuesday, less than two weeks after the country's top court allowed them to be eased.

As per the curbs, which fall under stage four of the Graded Response Action Plan (Grap), most schools have shifted to hybrid mode, all construction and demolition activities are banned, while the entry of lorries and heavy vehicles, except those carrying essential goods, has been prohibited.

Manish Adhikari, a resident, told news agency ANI that it has now become difficult to survive the winter in Delhi with constantly rising pollution.

Another resident, Bhagat Singh, also expressed his frustration.

"Pollution has become an incurable disease, especially for Delhi. There is no solution to it," he said. — BBC