Air pollution returned to Bangkok, Thailand, on Thursday (January 14) as a cold weather front from China weakened.

Footage shows the toxic smog formed from harmful PM2.5 particles filling the air of the capital during morning rush hour.

Atthaphol Charoenchansa, director-general of the Pollution Control Department, warned residents of an increase in PM2.5 dust in the atmosphere.

He said that the weakening of the cold front will slow air circulation, causing airborne dust particles to accumulate and drop to a lower altitude, which will worsen on Friday.

He urged motorists not keep the engines of their cars running while parked and farmers not to burn agricultural waste in open fields, while everyone should reduce outdoor activity.