Prolonged exposure to high air pollution, similar to what Delhi is experiencing now, is not only harmful to respiratory health but can also trigger cardiac, neurological and gastric problems, impacting productivity of people, experts said. The dust pollution from construction sites due to rampant ban violations also puts the health of people at risk, they said.

Exposure to high pollution levels worsens existing respiratory illnesses and contributes to new cases, said Dr Subhash Giri, medical director of Guru Teg Bahadur (GTB) and Rajiv Gandhi Super Speciality Hospital, two of the biggest state government-run hospitals in the city.

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Besides impacting the respiratory system, long-term exposure to air pollution, including dust from construction activities in this weather, also triggers heart and neurological problems such as cardiac arrests, strokes and gastric distress, he said.

Apart from emissions due to vehicles and heavy machinery such as nitrogen oxides and sulphur dioxide, silica dust pollution exposure around construction sites has its short- and long-term side effects.

“Spending long periods in such poor quality air would result in lowered work output and concentration levels, and people can also experience bouts of depression,” Dr Giri said. “One of the most dangerous results of long-term exposure to pollution is cancer.”

Every year at the onset of winter, air quality in the capital deteriorates, climbing to toxic levels. Smoke from stubble fires in the neighbouring states of Punjab and Haryana, emissions from Diwali firecrackers and Delhi’s local pollution sources are made worse by cooler temperatures and calm winds that do not allow the pollutants to disperse.

While the city experienced a fairly clean post-Diwali period this year, air quality over the past few days has touched alarming levels. Its impacts are being seen in the outpatient departments of hospitals, doctors said.

There is marked rise in cases of chronic obstructive pulmonary disease (COPD)—a chronic inflammatory lung disease that causes obstructed airflow—and asthma, according to Dr Neetu Jain, senior consultant, pulmonary, critical care and sleep medicine at PSRI Hospital. There is also a rise in patients coming in with pneumonia in both lungs, she said.

“Prolonged effects of pollution exposure would be a spike in the cases of lung cancer in the coming years,” Dr Jain said. “Longevity is also impacted by such exposure.”

Over half the cases of COPD in India is attributable to ambient and household air pollution, according to a 2018 Lancet Global Health research paper . In developed countries, 80% of COPD is caused by smoking, according to the paper.

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There was a 20% increase in the number of patients seeking emergency care for acute respiratory symptoms even when the air quality dipped slightly into the poor category, with PM2.5 (particulate matter less than 2.5 microns thick) levels recorded between 50 and 100 micrograms per cubic metre, a 2020 study by researchers at the All India Institute of Medical Sciences found.

At its peak, between October and January, when Delhi typically records PM2.5 levels of around 400 micrograms per cubic metre, this number goes up to 40%, according to the study.

Dr Vivek Nangia, principal director and head, pulmonology, Max Super Speciality Hospital, Saket, said people with comorbidities must avoid outdoor activities when the AQI crosses the 200-mark and healthy people must avoid outdoor exposure when the AQI crosses 300.

“If this is not possible, people must wear an N95 mask. Surgical masks don’t work in such high pollution levels,” said Dr Nangia.