Around 20 million people in India’s capital woke up 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. New Delhi’s PM 2.5 concentration—a measure of pollutants in the air—was more than 40 times the World Health Organization’s annualized guideline level, according to Swiss air quality monitoring company IQAir. In 2020, authorities enacted a complet