At the monitoring station at No 556 Nguyen Van Cu Street, the air quality index (AQI) was 210. The station at the US Embassy reported the AQI at 6 am on the same day at 262, very harmful to health.

PAMAir showed that the AQI in 60 points in Hanoi were 150-200 (red level) and 200-300 (violet).

According to the US classification, an AQI at 200-300 means the air quality is very bad, and that sensitive groups of people (elderly, children and people with respiratory disease) should stay at home. According to the Australian classification, air quality is very bad when AQI is just over 150.

Experts think air pollution recently had relations with temperature inversion which occurs in winter. A similar period of serious air pollution occurred in late September.

Le Thanh Hai, General Secretary of the Vietnam Association of Meteorology and Hydrology, said in the atmosphere layer of 300-1000m in height, there is low-layer fog.

Experts think air pollution recently had relations with temperature inversion which occurs in winter. A similar period of serious air pollution occurred in late September.

As a result, the pollutants cannot diffuse, but stay close to the ground. This mist forms at night and in the morning, but dissipates in the afternoon. The pollution is most serious at night and early morning, and improves in the afternoon.

When the spell of air pollution occurred in September, Hoang Duong Tung, chair of the Vietnam Clean Air Network, commented that this is an abnormal phenomenon and it is necessary to conduct thorough monitoring and further research.

Currently, Vietnam still cannot take stock of polluting sources, so it cannot place priority actions. Vietnam also lacks facilities to carry out long-term solutions to mitigate air pollution.

There are only two fixed monitoring stations in Hanoi which can provide reliable figures, while there is no such station in HCM City. Vietnam still cannot give forecasts about air quality because of the lack of monitored figures.

The air pollution in Vietnam is mostly PM 2.5 dust pollution. Direct contact with PM2.5 can lead to serious respiratory, cardiovascular and neurological diseases. PM2.5 pollution index at 12 micro-grams per cubic meter is considered a safe level for health. This index is equivalent to AQI level of 50.

Thien Nhien

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