The latest forecast from HanoiAir, an AI-powered air-quality model developed by the Intelligent Geospatial (GEOI) research group at Vietnam National University, shows the current smog wave began on Nov. 28 and may linger until Dec. 5.
On Monday, the citywide average AQI hit 143, a "poor" level that reflects PM2.5 concentrations of 77 µg/cu.m, roughly five times higher than the World Health Organization’s guideline of 15 µg/cu.m.
Monitoring stations operated by the Environment Department also recorded readings rising quickly into the "unhealthy" and "very unhealthy" ranges across several districts. These numbers track PM2.5, the microscopic pollutant now considered the most dangerous component of urban smog.
A widely cited 2015 study by Berkeley Earth found that breathing air with PM2.5 at 22 µg/cu.m for 24 hours causes lung and cardiovascular damage similar to smoking one cigarette. By WHO’s standard of 15 µg/cu.m, the "exposure equivalent" is roughly 0.7 cigarettes. The comparison is rooted in health impact, not chemistry: fine dust and tobacco smoke are different, but their cumulative harm overlaps in troubling ways.
Using this conversion and PM2.5 data collected by ward and commune in 2024, GEOI researchers estimate that the average Hanoi resident is effectively "inhaling" two cigarettes’ worth of fine dust every day, tied to an annual average PM2.5 concentration of about 41 µg/cu.m. On heavily polluted winter days, that figure can spike sharply.
The scale of the problem is far from abstract. WHO has repeatedly called air pollution a "silent killer." World Bank data from 2021 show that 40% of Hanoi’s population, some 3.5 million people, were exposed to PM2.5 levels above 45 µg/cu.m, five times the global benchmark. PM2.5-linked causes accounted for an estimated 32% of all deaths in the capital, or around 5,800 fatalities per year.
Doctors are already seeing the consequences. Doan Du Manh of the Vietnam Vascular Disease Association says breathing outdoor air during severe pollution episodes "causes harm comparable to smoking two packs of cigarettes a day."
PM2.5 particles, about 1/30 the width of a human hair, can slip deep into the lungs, inflame the trachea and bronchi and lodge in the alveoli, where they trigger long-term scarring. Spikes in respiratory infections, strokes, and heart attacks reliably emerge between September and December, the collision point of winter weather and peak pollution.
Sensitive groups are hit hardest. Older adults, children, pregnant women and anyone with respiratory conditions are prone to recurring sinusitis, sore throat, or even acute bronchopneumonia on the worst days.
The exposure burden is not unique to Hanoi. Data from AirVisual and GEOI since 2019 show that during peak pollution months, residents effectively inhale the equivalent of three to four cigarettes per day.
Globally, Hanoi ranks seventh in AirVisual’s 2024 report, with PM2.5 levels of 45.4 µg/cu.m. New Delhi tops the list at 91.8 µg/cu.m, roughly 4.2 cigarette equivalents, followed by N’Djamena in Chad at 91.6 µg/cu.m.
Air pollution in Hanoi between 2019 - 2024
Still, experts caution against over-literalizing the cigarette comparison.
Manh stresses that Berkeley Earth’s formula is a reference tool; real health impacts vary based on genetics, climate, and individual exposure patterns.
"Office workers face lower risks than people working at construction sites," he notes. Vietnam, he argues, needs more local research tailored to Vietnamese physiology and environmental conditions.
Associate Professor Nguyen Thi Nhat Thanh of the GEOI team warns that air-quality deterioration is no longer limited to Hanoi or northern provinces. Ho Chi Minh City and its neighboring regions are also seeing worsening patterns.
"When a major city lands on the global pollution rankings, it forces us to pay attention; but by then, it’s often too late for meaningful prevention," she says.
Forecasting tools can help. Today, air pollution can be predicted 7–9 days in advance, and experts say checking AQI should become as routine as checking the weather. That shift in daily habit, they argue, is essential for self-protection.
Authorities are responding with emergency measures. Since Nov. 27, the Ministry of Agriculture and Environment has urged the Ministry of Industry and Trade to direct steel, chemical, fertilizer and thermal-power plants in northern Vietnam to cut output or delay major maintenance during days when AQI exceeds 200. The Ministry of Education has advised schools to limit outdoor activities whenever air quality reaches "unhealthy" levels.
Under Vietnam’s National Action Plan for Air Quality Management (2026–2030), Hanoi must cut PM2.5 concentrations by 20% from 2024 levels and increase the number of "good" or "moderate" air-quality days to at least 80%. By 2045, the city is required to meet the national annual PM2.5 standard of 25 µg/cu.m.
(From L) Heavy smog in Hanoi in 2019, 2023 and 2025. Photos by Thanh Hai
Quang Tue, Phung Tien, Thanh Ha
