Pollution in the Indian capital, New Delhi, rose to a “severe” level on Thursday after revellers let off fireworks long into the night to mark the Hindu festival of Diwali.
Two federal government pollution indices showed air at “very poor” and “severe” levels, indicating that prolonged exposure could lead to respiratory illnesses.
The indices mostly measure the concentration of tiny poisonous particulate matter, or PM 2.5, particles that are less than 2.5 microns in diameter, which can be carried deep into the lungs.
The US embassy said PM 2.5 levels in its part of central Delhi had soared to 689, indicating emergency conditions, posing a serious health risk.
A level of 50 or less is considered safe.
A taskforce under the federal pollution control board was scheduled to meet to assess the situation, a city government spokesperson told Reuters.
After the Diwali festival, levels of airborne PM 10 and PM 2.5 touched 470 and 322 respectively, up from 438 and 180, the Central Pollution Control Board said in a bulletin.