Indian authorities have ordered firefighters in the capital to sprinkle water from high-rise buildings to settle dust and stop garbage fires and have banned construction activity as hazardous air quality affects millions of people.

New Delhi recorded one of the highest pollution levels of the year on Sunday with the air quality index, measuring sulfur dioxide, carbon monoxide and nitrogen dioxide, touching 450.

The air started improving Wednesday with an increase in wind speed. However, the level of PM 2.5, tiny particulate matter that can dangerously clog lungs, exceeded 320 yesterday, more than 13 times beyond what the World Health Organization considers safe, according to the U.S. Embassy reading.

A government advisory asked people to avoid jogging outdoor and use masks. The government has banned diesel vehicles that are more than 10 years old. It also ordered builders to cover construction sites to stop dust enveloping the area.

"There are so many cars ... there is so much dust. It all goes inside [our body]. If we don't wear a mask then we face a lot of [health] problems," said Om Prakash, a traffic police constable wearing a protective mask on a New Delhi road.

India's air pollution comes mostly from diesel fuel-burning vehicles, coal-fired power plants and crop burning. It worsens in the dry winters, as winds die down and pollution pools over the Delhi plains.

Vehicular smog mixes with smoke from festival-season fireworks as well as countless illegal pyres of garbage burned by homeless migrants to stay warm as temperatures near freezing. And the construction sends up clouds of dust. NEW