Hospitals across New Delhi reported a sharp rise in patients with breathing difficulties on Friday as a thick layer of smog settled over the Indian capital. Readings at several monitoring stations approached the 'severe' category two days before Diwali. Doctors at AIIMS New Delhi and Safdarjung Hospital said outpatient chest clinics were seeing noticeably more people with asthma attacks, bronchitis and flare-ups of chronic obstructive pulmonary disease.

The Central Pollution Control Board's 24-hour average air quality index for Delhi stood well above 350, in the 'very poor' band, according to the board's daily bulletin. Several stations, including Anand Vihar and Wazirpur, recorded readings above 400. Concentrations of PM2.5, the fine particles that lodge deep in the lungs, ran many times above the safe limit set by the World Health Organization.

The India Meteorological Department said calm winds and falling night-time temperatures were trapping pollutants close to the ground. Satellite data cited by the Indian Agricultural Research Institute showed continued crop-residue fires in Punjab and Haryana, whose smoke drifts towards the capital each autumn. The Commission for Air Quality Management kept emergency curbs under its Graded Response Action Plan in force across the National Capital Region and warned that tighter measures would follow if readings worsened.

Physicians urged children, older people and those with heart or lung disease to limit time outdoors, avoid early-morning exercise and wear N95 masks. Paediatricians in the city said they were treating more young children for persistent coughs and wheezing. Delhi's health department advised hospitals to keep respiratory beds and nebulisation services ready over the festival weekend.

The pollution spike came as Diwali celebrations on Sunday threatened to add firework smoke to an already toxic mix. Air quality in Delhi has deteriorated after the festival in most recent years, and forecasters at the Ministry of Earth Sciences' Air Quality Early Warning System said conditions were likely to remain 'very poor' or worse into next week.