Meteorologists debate cause of fog in Ho Chi Minh City hinh anh 1Thick haze shrouds downtown Ho Chi Minh City early Tuesday morning (Photo: VNA)

HCM City (VNS/VNA) -
Meteorologists are debating the cause of the thick fog that has blanketed HCM City and some southern provinces in recent days, which has triggered concerns of residents about worsening air quality.

Smog has covered a wide area of the city, especially in the area adjacent to the Sai Gon River of Binh Thanh, District 1 and 2, since early September 21 morning. 

Poor visibility was reported as buildings could not be clearly seen from further than 100 metres at 10am.

The air quality index (AQI) was measured between 111 and 153 on September 20-22 by AirVisual, levels which have bad impacts on human health.

The AQI measured 128 and 132 on September 23 and 24 respectively. Southern provinces such as Binh Thuan and Ca Mau reportedly suffered the same situation.

Ho Quoc Bang, head of the air pollution and climate change office at the HCM City National University’s Institute for Environment and Natural Resources, said the office has applied an air quality model with a simulation of how air pollutants disperse and react in the atmosphere to trace the cause of the foggy weather.

The results showed the fog was mainly caused by forest fires in Indonesia.

On September 18, widespread fires engulfed Indonesia’s forests, spewing toxic haze across the region, including HCM City. Thus, the city’s air quality index (AQI) was alarmingly high on September 20.

Four days later, the AQI remained high.

Other elements, including high humidity, the tropical convergence zone caused by low daytime temperatures stopping pollutants rising, and emissions from people’s everyday activities, also contributed to the thick fog.

However, Le Dinh Quyet, deputy head of Centre of Hydrological Forecasting for the southern region, told Vietnam News Agency there was not enough evidence to claim the forest fires in Indonesia were to blame.

From a meteorology perspective, he said high humidity measuring between 95 and 100 percent, low daily temperatures and heavy rainfall have caused the haze.

He suggested an environmental agency measure dust levels in the air and assess its health impacts.

Deputy director of the Vietnam Environment Administration Nguyen Hung Thinh said more reliable evidence is needed to determine the impact of Indonesia’s forest fires on the city’s smog.

The sudden change of weather from hot to cold due to cold spells would lead to a change of humidity, causing fine dust pollution.

Hanoi and HCM City are being affected by the northeast monsoon, which has caused weather phenomena of air pollution and seriously affected human health, the Vietnam Environment Administration has said.

The recent concentration of fine dust has reportedly increased dramatically and the AQI was measured high by many air quality monitors.

In Hanoi, the AQI level was at 150-170 on September 15-16. The level was 128 and 132 in HCM City on September 23 and 24. Outdoor exercise should be limited for children and people with respiratory problems.

According to the Ministry of Natural Resouces and Environment, several measures need to be implemented to reduce air pollution in big cities. 

Public transport should be used instead of personal vehicles, solutions to restrict vehicles to operate in the inner city should be studied and the production and use of eco-friendly means of transport should be promoted.

It is necessary to relocate industrial businesses from the inner city to industrial parks in suburban areas and minimise waste produced by construction activities.

In addition, it is important to inspect vehicles that cause air pollutants. 

A comprehensive system of equipment and software for modelling air quality should be employed to improve the monitoring capacity, it said./.