Experts term this to be late onset of asthma, which is otherwise a chronic disease, due to the increasing levels of air pollution in Indian cities.

"More and more patients who have never got asthma before are coming to us with this disease. This can be only attributed to the rising levels of pollution in the air," Ujjwal Parikh, consultant chest medicine, Sir Ganga Ram Hospital, told IANS.

"Incidents of asthma overall are also increasing. Air pollution is one of the triggering factors. People who are exposed to vehicular pollution and dust are most prone," he added.

Rajesh Chawla, senior consultant with the Indraprastha Apollo Hospital, told IANS: "Pollution definitely aggravates asthma. It is one of the major triggers. Incidents of asthma have in fact increased over the years."

Echoing this, Vivek Chhattopadhyay of the Centre for Science and Environment (CSE) said that several research studies also indicate that pollution triggers asthma as well as low lung function, especially in children.

"Air pollution is a rising concern. It definitely aggravates asthma. Studies indicate that there is a variety of health impacts of air pollution," he said.

A study conducted in Delhi by the Central Pollution Control Board (CPCB) and Kolkata-based Chittaranjan National Cancer Research Centre found that every third child in Delhi had reduced lung function due to air pollution.

Chhattopadhyay said children in the national capital, where CPCB found "critical" particulate levels, are the most vulnerable.

"Poor air quality affects kids' capacity to breath leading to increase in respiratory problems. It affects their growth," Chhattopadhyay told IANS.

Citing a scientific judgement, Chhattopadhyay said children's breathing depends on per kg of body weight.

"Kids breath more for each kilogram that they gain during the growing age. While they breath more, they inhale more pollutants. And they also play outdoors. Keeping all these factors together, children are the most vulnerable group along with older people," Chhattopadhyay said.

Vivek Singh, consultant at the pulmonology department at Gurgaon's Columbia Asia Hospital, told IANS: "Even the normal population these days gets affected due to air pollution."

Asthma is a chronic disorder of the lungs, where inflammation and narrowing of the airways happen. And when the air is polluted the allergens present like smoke, dust, toxic gases like carbon monoxide and nitro-oxide affect asthma patients with aggravated levels of asthma.

"Air quality these days is pretty bad due to the ongoing construction work in and around Delhi NCR, vehicular pollution and industrial pollution," Vivek Singh said.

"Burning of crops has also led to increased smoke in the air making it difficult for people suffering from asthma and worsening their condition and losing control of their asthma," he added.

According to the World Health Organization, Indian cities, including Delhi, are among the most polluted.

Taking note of the rising levels of air pollution, the National Green Tribunal has taken steps like banning diesel vehicles older than 10 years from entering the capital and making burning of waste a punishable offence.

Although the fundamental causes of asthma are not completely understood, the strongest risk factors for developing asthma are inhaled asthma triggers, which include indoor allergens (house dust mites in bedding, carpets and stuffed furniture and pollution), outdoor allergens (such as pollens and moulds), tobacco smoke and chemical irritants in the workplace.

During an asthma attack, the lining of the bronchial tubes swell, causing the airways to narrow and reduce the flow of air into and out of the lungs.

Doctors say that though there are no particular ways of preventing the disease, it can be effectively managed by taking certain precautions.

According to Parikh, unnecessary travel should be avoided during peak traffic hours and care must be taken to drive with the car window up.

"While travelling in a car, the air conditioner should be put on the re-circulate mode so that the outside air does not come in," he said.

The majority of the first time patients, according to Parikh, are youngsters.

Vivek Singh said: "There are some ways with which people can keep asthma under control."

"Once in a while, go to places with clean air quality like hill stations where clean air is available. I have personally seen some patients coming back from places with clean air and no episodes of asthma.

"Educative efforts of awareness need to be done on both individual and organizational levels. People need to avoid maximum exposure to such polluted conditions; or wear an N90 mask for protection or wear a wet handkerchief to filter dust particles," Vivek Singh added.