In 2023, the world’s air pollution crisis hit a new high, with New Delhi, India’s capital, ranking as the most polluted capital city. According to the World Air Quality Report from IQAir, New Delhi’s air had an average PM2.5 concentration of 92.7 micrograms per cubic meter, which is over 17 times the limit recommended by the World Health Organization (WHO). PM2.5 particles, the most harmful pollutants in the air, are so tiny—less than 2.5 micrometers across—that they can easily enter the lungs,...