Heavy traffic as people return to Hanoi after the Lunar New Year holiday,
January 29, 2020. Photo by VnExpress/Ngoc Thanh. 

Hanoi will get 70 more air monitoring stations this year as it continues to be plagued by poor air quality, authorities say. 

Fifty would be set up at various locations by the first quarter, the city Department of Natural Resources and Environment said at a meeting on Wednesday.

The remaining 20 will be installed by the end of the year. They will take the total number to 81.

The installation will be done by THT Development Company Limited, owned by South Korea's DaeWoo E&C Vina company.

According to the department, the air quality was at "good" levels, the best in many years, during the Lunar New festival from January 23 to 29 thanks to the long spells of rain and people leaving the city.

But as people returned to work after the holiday, the AQI levels worsened again.

Air Visual's AQI ranking on Thursday showed Hanoi to be the 11th most polluted city in the world with a reading of 142. A reading of above 100 is considered unhealthy for humans.

Air quality was at unhealthy levels at various spots in Hanoi at 4 p.m.
on February 6, 2020, according to Air Visual.

Vietnam’s capital has been suffering from long periods of severe air pollution since September last year.

The PM2.5 particulate level reached a five-year high in September and environment officials urged residents to limit outdoor activities. PM2.5 refers to superfine particles that are 3 percent the size of a human hair.

The capital’s AQI went past 200 for four consecutive days starting on November 7 before topping 300 on November 12, according to the department. 

Authorities have blamed the pollution on vehicle emissions, domestic cooking coal, construction, and livestock.