NEW DELHI — With air quality reduced to ‘‘very severe’’ near the Indian capital, authorities are bracing for a major Hindu festival featuring massive fireworks that threatens to cloak New Delhi with more toxic smog and dust.

India’s pollution control board on Friday said New Delhi’s air quality had plummeted to the worst possible category. The level of tiny particulate matter that can dangerously clog lungs was 187, more than six times higher than what is considered safe.

The board warned people to avoid jogging outdoors in the early morning and after sunset, and to keep medicine nearby if asthmatic.

The most recent air pollution data from the World Health Organization released in March gave India the dubious distinction of having the world’s 10 most polluted cities.

India’s capital, which once was the world’s most polluted city, ranks sixth. But experts say the data does not suggest that New Delhi’s air quality has improved, but rather that other Indian cities’ air has worsened.

Associated Press