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Greenery and fine dust
By Nguyen Minh Hoa
Sunday,  Jan 12, 2020,12:29 (GMT+7)

Greenery and fine dust

By Nguyen Minh Hoa

In this situation, real trees will give much better comfort than artwork of greenery - PHOTO: THANH HOA

After green trees have been felled, fine dust will go straight into the city, instantly and directly into people’s mouths, noses and lungs.

From December 8 to December 15, 2019, Hanoi suffered from multiple outbursts of air pollutants, in fact they were the worst in the city’s history. The air quality index (AQI) was constantly at the purple level (very unhealthy), sometimes even reaching the highest pollution threshold—the brown level (hazardous). This level gives a warning that air pollution affects the health of all residents, especially the elderly, children and those with chronic respiratory diseases. Such heavy pollution has emerged in recent years and worsened over time. Despite this, the government of Hanoi seems helpless when it comes to taking immediate countermeasures, able to do little other than giving citizens advice to wear masks when going out, and those with respiratory diseases to stay home.

Where is fine dust from?

Air pollution in a city is caused by several factors, and the severity varies with weather and seasons. There are 12 sources of air pollution, said Chairman Nguyen Duc Chung of the People’s Committee of Hanoi, including the permanent pollutants emitted every day from millions of cars and motorbikes, along with dust clouds from construction sites and manufacturing plants. There are also seasonal particulate pollutants, for instance when Hanoians burn joss paper all at once. Furthermore, scholars have identified some “incredible” causes, such as the streets in Hanoi have not been washed for a long time, or the city is covered in dust as a result of too many households doing year-end cleaning at the same time, etc.

The most dangerous thing from environmental pollution in Hanoi is currently fine dust. According to experts, in addition to emissions, organic and inorganic dust, there is a special kind of dust in the air of Hanoi—fine dust. There are two types of fine dust, PM10 and PM2.5, with the latter being the most harmful. In this sense, tiny particles float freely in the air—they are around 2.5 microns or smaller, approximately 30 times finer than a human hair. This kind of dust may penetrate deep into the lungs, badly affecting human health. It is the cause of many respiratory diseases such as pneumonia, bronchitis, or asthma, etc.

Then, where does fine dust come from? Among the 12 sources of air pollution in Hanoi, the first and direct cause relates to factories and industrial parks across the city, said Chairman Chung. Tran Dinh Sinh, deputy director of Green ID, said, “Dust clouds from factories are brought to Hanoi by the wind. From cement plants in Ha Nam, Ninh Binh and Lang Son—if there is tailwind—the dust will scatter everywhere, gathering in Hanoi causing air pollution.”

The question is cement and coal-fired power plants have been around for decades, but how come they are only sending fine dust into the capital city now. The cement factories of

Vissai Group in Ninh Binh, for example, were set up in 2007-2009 and located about 90 kilometers from Hanoi.

As per the results of the state-level research project coded 07.11, led by Pham Ngoc Dang, after 10 years of development (1986-1996), the four former urban districts of Hanoi lost 12% of their greenery, and the water surface of ponds and lakes shrank by 64.5%. Meanwhile, the area of buildings increased 22.4%. There have been no statistics for the period from 1996 until now, but activities like erecting rows of high-rise blocks, expanding the streets and building a tangle of bridges that looks like a bowl of spaghetti (like how urban planners describe) have resulted in a drastic reduction in greenery and water surface. For instance, 1,300 trees were cut down to expand Ring Road No. 3 in 2016; 500 trees along the To Lich River were felled in the development of Ring Road No. 2 in 2018; and numerous trees along the streets, in residential areas and around office buildings have fallen victim to urban development, most of which were perennials with a great height and canopy.

Scientifically speaking, all trees up to four meters tall or more and a dense canopy help prevent fine dust both vertically (from the sky) and horizontally (from one place to another), cast it away faster and reduce its movement speed. When there is rain or water from water trucks, fine dust is easily washed into the sewerage system. Trees with a thick canopy and the green belt around a city serve as an umbrella, or, so to speak, an armor to protect all of its residents. When trees have been chopped down, fine dust will go straight into the city, instantly and directly into people’s mouths, noses and lungs. Notably, on cold days, when there is no wind, no rain, and the temperature is low and humidity is high, the air will be congested and pollutants cannot come higher or move away.

In such an environment, fine dust remains at the lower layers of the atmosphere for a long time, hovering at 2-3 meters above the ground, just about the range for it to be breathed in by humans. If one looks down at the city of Hanoi on foggy days aboard an airplane, they will see the dust form a very curious pattern. High-rise buildings around the downtown cause Hanoi to look like a bowl placed upside down. Fog and smoke create a thick layer of air that resembles a lid on the bowl, keeping fog and smoke within. If this situation repeats time and again, many Hanoians will fall ill due to dust and emissions as in annual reports by the Ministry of Health.


To tackle air pollutants, Hanoi should learn from Beijing, China. Beijing was one of the 20 most polluted cities in the world, but in recent years, the situation has improved significantly. The city is determined to strictly deal with sources of air pollution by imposing a restriction on private transport means, forcing people not to use coal for cooking or heating in winter, shutting down 2,500 factories that discharge smoke into the air, relocating all polluting facilities, and especially on March 18, 2017, shutting down Beijing’s last coal-fired power plant. Beijing’s fine dust concentration has declined 35% and is on track to fall further. Lately, Beijing has been removed from the list of the 20 most polluted cities in the world.

To avoid facing the same situation as Hanoi, HCMC should also review its environmental protection strategies. Before 1990, the city was protected by a green belt combined with rivers and canals, but now there are only small fragments of them left. In addition, if the reclamation program to develop a city in Can Gio with a scale of nearly 3,000 hectares, for 300,000 new residents (who are not Can Gio people) and 1.2 million tourists each year, is not properly controlled, it will have a severe impact on Can Gio Mangrove Forest, which has been long considered the shield of HCMC. Recently, a leader of HCMC said urban development would take place in four out of the city’s five suburban districts. If this is true, the ecological, agricultural belt surrounding the city would be abolished, like how skin and fat are removed from one’s body. Then, HCMC would meet the same fate as Hanoi, or even worse for thermal power plants to be set up in Long An are just 30 kilometers from the city to the south and industrial parks in Binh Duong and Dong Nai are only 40 kilometers to the north.

The best measures are to eradicate the facilities that are the source of harmful emissions. Still, it seems to be far from simple to immediately abandon coal-fired power plants, shut down those cement plants with a vertical shaft kiln, get rid of hundreds of thousands of honeycomb charcoal stoves in Hanoi, ban millions of farming households from burning straw post-harvest, and prohibit the use of millions of motorbikes, etc. That said, one thing can be done now—stop the demolition of urban greenery and find ways to recover and expand it effectively.

At the scientific conference named “40 Years of Can Gio (Duyen Hai) and HCMC—Achievements and Experiences” held in December 2018, HCMC Party Secretary Nguyen Thien Nhan said, “If we (the city’s leadership) take a wrong decision, the consequences may not be apparent in 5-10 years, but the devastation will be terrible after that, and the future generations will curse us.”

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