Health experts have warned that air pollution in India's capital Delhi has reached dangerous levels following Diwali celebrations, with hospitals reporting a sharp rise in patients suffering from respiratory illnesses, The Independent reports.

Hospitals across the city have seen an influx of patients experiencing breathing difficulties, persistent coughing and other respiratory problems since the weekend, when fireworks during the Hindu festival of lights further worsened air quality.

The Central Pollution Control Board recorded an Air Quality Index (AQI) above 400 in several parts of Delhi on Sunday evening, placing the city in the severe category. Meanwhile, readings from private monitoring platforms reportedly exceeded 2,000, reaching hazardous levels.

The national AQI scale maintained by the central pollution board is capped at 500. At such severe levels, air pollution can cause respiratory problems even among healthy people and seriously affect those with existing heart and lung conditions.

Dr Vijay Hadda, a professor of pulmonary medicine and sleep disorders at the All India Institute of Medical Sciences in Delhi, expressed concern over the worsening situation.

“I am honestly surprised that we are still alive. I don’t think this kind of air is suitable for human survival,” he was quoted as saying in local media.

He warned that residents were continuously exposed to polluted air, making everyday life increasingly difficult.

“This happens every year but somehow we all forget. The general public forgets, and even policies remain somewhat in a grey area,” he said.

According to doctors, breathing Delhi's severely polluted air in previous years has been compared to smoking 25 to 30 cigarettes a day.

The pollution has worsened despite measures introduced to limit the impact of Diwali fireworks. In October, India's Supreme Court mandated the use of approved green firecrackers under specified conditions, allowing fireworks for three-hour periods on Saturday and Sunday.

Although green firecrackers produce fewer emissions than conventional fireworks, they still release particulate matter and other pollutants.

According to Swiss air quality monitoring agency IQAir, concentrations of fine particulate matter known as PM2.5 reached 879 micrograms per cubic metre in some parts of Delhi on Monday. The level was nearly 59 times the World Health Organization's recommended daily limit.

PM2.5 particles are small enough to penetrate deep into the lungs. Prolonged exposure can increase the risk of respiratory infections, cardiovascular diseases and lung cancer. Emerging research has also linked exposure to pregnancy complications, fertility problems and type 2 diabetes.

Children, pregnant women, older people and those with existing health conditions are particularly vulnerable. However, doctors have warned that healthy adults are also experiencing the effects.

Dr Arjun Khanna, head of pulmonology at Amrita Hospital, said repeated exposure to air pollutants could trigger chronic inflammation and damage lung tissues, gradually reducing breathing capacity.

Dr S Chatterjee, a senior consultant in internal medicine, said people aged between 20 and 50 were also experiencing pollution-related health problems.

He warned that high pollution levels could trigger symptoms in otherwise healthy individuals within four to six hours, adding that the effects could persist even after initial exposure.

The impact on children has also raised concern among medical professionals.

Paediatrician Sameer Maqsood told The New Indian Express that he was seeing more than 35 to 40 children with respiratory problems every day.

“Newborns are requiring frequent nebulisation and even hospitalisation. Apart from cold and cough, lots and lots of kids are coming with breathing difficulties,” he said.

Delhi and its surrounding National Capital Region, home to more than 30 million people, routinely experience severe air pollution during winter.

The situation is aggravated by Diwali fireworks, cooler temperatures and smoke from agricultural residue burning in neighbouring states, particularly Punjab and Haryana.

A 2024 study published in The Lancet estimated that air pollution was linked to 3.8 million deaths in India between 2009 and 2019.

Amid the worsening conditions, doctors have advised residents to limit outdoor activities and wear N95 masks when going outside.

The government has also asked schools in and around Delhi to shift classes online and encouraged people to work from home to reduce exposure to the polluted air.