Wind and rain won't save Hanoi from fine dust

Aware of the health risks, locals try to protect themselves with masks and air purifiers.

My friends and family often complain about the pollution, and sometimes hope for heavy rain to clear the air in the mistaken belief that rain can wash away air pollution.

A 10-minute downpour may briefly reduce fine dust, but it does not solve the problem. If rain were effective against air pollution, Vietnam's high annual rainfall would have already done that.

At best, rain offers temporary relief, not a solution.

Hanoi shrouded in unclear sky at noon on Nov. 18, 2024. Photo by VnExpress/Pham Chieu

A study in China found 27-36% of fine dust is blown away by winds that come with rain, but returns afterward.

Fine dust is a persistent pollutant. It accumulates in the air year after year, making pollution progressively worse.

PM2.5 particles are so small they are invisible, meaning Hanoi's haze is not just from PM2.5.

The main culprits are PM10 particles and larger pollutants, including dust, pollen and ash. While PM10 is harmful, PM2.5 is even more dangerous, reaching deep into the lungs and bloodstream, increasing the risk of heart disease, stroke and lung cancer.

The city's pollution may be worse than it appears—about 60% of household dust comes from outdoor air, while the remaining 40% has built up over the years despite regular cleaning.

When I bought an air purifier in Vietnam, PM2.5 levels in my home stayed below 10. But after deep cleaning, the dust got stirred up, and using a fan to dry the house made it worse. PM2.5 levels shot past 100, sometimes exceeding 200. A level below 10 means clean air, while over 100 is unhealthy, and 200 is hazardous.

No matter how much I clean, dust keeps returning.

Many think air pollution is just about dust, but airborne metal particles and harmful microbes pose even greater threats. Dust can cause respiratory issues, but bacteria and viruses in the air spread infections and diseases.

A 2006 U.S. study found up to 1,800 bacterial species in the air. When walking past garbage dumps, people do not just inhale bad odors; they breathe in six types of harmful microbes that affect the lungs and heart.

Traditional ceremonial paper burning exposes people to high levels of carbon monoxide and metal particles like aluminum and copper.

To tackle fine dust, we must first recognize this is not just Hanoi or HCMC's problem.

National fuel and vehicle standards need to be stricter.

Between 1998 and 2018 China made emission standards increasingly strict five times and upgraded fuel quality six times. High-emission vehicles were identified and gradually phased out.

By 2013 all such vehicles were banned, cutting pollution by 40% from 1998 levels. Yet Beijing continued to suffer from smog, leading officials to acknowledge that air pollution was a regional issue.

The Chinese government then formed an anti-pollution alliance of 28 cities, including Beijing, Tianjin and Hebei. By 2021 Beijing met China's air quality standards, with PM2.5 levels averaging 30 μg/m3.

The World Bank estimates that only a third of Hanoi's fine dust comes from within the city—the rest blows in from nearby provinces and even across borders. A regional alliance may be necessary to control pollution at its source.

Stronger action is also needed against other pollution sources. Open burning of waste and straw in Vietnam must be banned nationwide, not just in residential areas and along highways. Once airborne, fine dust can travel hundreds of kilometers.

Vietnam must also enforce construction dust regulations more strictly.

Water spraying and barriers help, but construction sites remain far dustier than for instance in Australia. Better materials and filtering systems can reduce dust, but enforcement matters most.

In Australia, projects violating dust regulations are shut down immediately, and Sydney fines polluters up to AUD5 million (US$3.16 million).

These penalties force compliance.

In Vietnam, contractors often ask residents to simply tolerate hazardous dust.

Half-measures will not solve the country's air pollution problem. Some cities have experimented with large outdoor air purifiers, but those can only clear a 20-meter radius and are expensive. Hanoi needs more green spaces, a better drainage system and frequent street cleaning. Regulations should require residential and commercial buildings to maintain a minimum green area, also known as green plot ratio.

China's experience shows that without strong and decisive enforcement of regulations, Vietnam's pollution will worsen by 15-20% annually.

No amount of wind or rain will fix it for us.

*To Thuc is a lecturer at James Cook University in Australia.