At Sunday noon, three monitoring stations run by the municipal Environment Department showed Air Quality Index (AQI) of above 200.
The AQI is a metric used to measure how polluted the air is. An AQI level above 100 is considered unhealthy for humans. Children, seniors, and individuals with respiratory and heart diseases are recommended to avoid sustained and high-intensity outdoor exercises when AQI levels reach 150 or above.
The stations in the districts of Bac Tu Liem, Ba Dinh and Dong Da had index readings of 232, 231 and 211, respectively. Another station in Cau Giay District recorded an index of 134.
The weather station of the U.S. Embassy in Hoan Kiem District revealed an index of 176.
Hundreds of stations of the Vietnamese environment monitoring app PAM Air, developed by Hanoi-based D&L Technology Integration and Consulting Joint Stock Company and launched in Vietnam in February, recorded the AQI index in most areas of Hanoi at "red" and "purple," which mean "bad" and "very bad," respectively.
The AQI readings at Ha Dong was 254, and Hoan Kiem 267.
The Switzerland-based air quality monitoring facility, IQAir AirVisual, ranked Hanoi the fourth most polluted city in the world with a Sunday AQI of 188.
It has forecast that air quality in the capital city will improve on Monday with an AQI of around 127 and increase again by Wednesday.
Hanoi is in its winter season now and the typical weather is dry with very little rain, which has contributed to the increase of fine dust.
Researchers from the University of Engineering and Technology under the Vietnam National University in Hanoi said earlier this month that Hanoi had the highest annual average fine particulate matter (PM2.5) concentration of all Vietnam localities in 2020.
The researchers were citing Vietnam's first national-scale study using the machine learning statistical model combined with satellite imagery to evaluate air quality even in areas without air quality stations.
From the beginning of November, the department has coordinated with a number of units to organize a pilot emission inventory with about 5,000 motorbikes. The results will be the premise for the city to come up with specific methods to reduce air pollution from traffic.
The Hanoi Department of Natural Resources and Environment has recommended that people limit the burning of garbage and reduce cooking with honeycomb charcoal. Suburban districts, meanwhile, should not burn straw to limit pollution, it said.