It is recommended that in order to protect themselves from exposing to the dangers of ultra-fine dust, adults, children, pregnant women, people suffering from respiratory diseases should wear masks and glasses when working outdoors.

Hanoi residents warned about air pollution. Photo: Pham Hung 

As concern is prevailing among Hanoi residents about the ongoing air pollution, the Ministry of Natural Resources and Environment (MONRE) has warned people to refrain from outdoor activities at this time, according to local media.

The MONRE reported from September 12 to September 29, PM2.5 dust particles in Hanoi’s air exceed the permitted level and reach the highest over the last five years.

PM2.5 particle concentration increases and maintains at high level especially at night and early morning (AQI> 100), sometimes even reaches bad level (AQI> 200). In the mornings from September 25 to October 1, it was reported that at some AQI monitoring stations, the PM2.5 concentration exceeded 200,  a bad level.

 Data from automatic air monitoring points in recent days show that air quality in many northern localities of Vietnam, especially in Hanoi, is at an alarming level.

 However, the MONRE said that bad AQI appears only at certain locations and at certain time, mainly in Hoan Kiem, Thanh Cong, Pham Van Dong, Hang Dau, Minh Khai, and the US embassy where the stations are located, from 0:00 am to 6:00 am.

 The ministry said that temperature inversion is one of the factors causing poor air quality in recent days coupled with little air circulation in the atmosphere during the transition between summer and fall.

 Temperature inversion contributed to the capital’s poor air quality in the way that thermal radiation is dispersed from the ground into the atmosphere, which causes fog at low altitude, preventing it from rising up into the atmosphere, the MONRE noted.

 It stressed that as air could not rise high by convection, so there is no cloud formation to produce rain and cleanse the atmosphere nor wind to disperse the polluted air.

 It is recommended that in order to protect themselves from exposing to the dangers of ultra-fine dust, adults, children, pregnant women, people suffering from respiratory diseases should wear masks and glasses when working outdoors, the ministry said.