Around 20 million people in India’s capital woke up on Wednesday breathing the most polluted air of any major city in the world, a day after celebrations for the Diwali festival, during which revelers typically set off fireworks and firecrackers.

With people across the national capital celebrating Diwali with fireworks on Monday night, Delhi’s air quality deteriorated, with most of the monitoring stations marked in the ‘red zone’.

“Over the past decade, researchers have been uncovering the biological mechanisms by which air pollution can contribute to autoimmune diseases like rheumatoid arthritis (RA), lupus, and multiple scler...