Delhi air quality worsens ahead of Diwali as firework restrictions enter force

Delhi is once again battling worsening air pollution as the onset of winter brings a familiar deterioration in air quality to India's capital.

The city's air quality index (AQI) - which measures PM2.5, fine particulate matter that can clog lungs - has crossed 300, entering the "very poor" category and raising health concerns for millions of residents.

Breathing such polluted air over prolonged periods can cause respiratory problems and worsen existing illnesses, with children and older people particularly vulnerable.