A report from AirVisual showed that Hanoi ranked second on the list of the world’s most polluted cities on Wednesday morning, up from fourth place recorded yesterday.
The PAM air quality system also recorded dozens of air pollution hotspots in the capital this morning, and the agency advised people to stay indoors to avoid health problems.
Many people were seen wearing thick face masks on local streets.
Many buildings can only be seen from a short distance.
The pollution worsened in construction and road work areas.
The sky became clearer by noon but air quality centres still reported bad indexes.
It is forecasted that the pollution may continue in Hanoi as well as some other northern localities. The most severe air pollution in the region often occurs from October to March.