Hanoi, the bustling capital of Vietnam, has taken an unwelcome title this January: the world’s most polluted city. According to air quality monitoring platforms such as IQAir and AirVisual, the city’s air quality index (AQI) repeatedly reached hazardous levels throughout the month, with PM2.5 readings soaring well above safe thresholds.
The city’s pollution problem highlights both environmental challenges and the health risks faced by its nearly 8 million residents.
On multiple days in January, Hanoi recorded PM2.5 concentrations exceeding 250 micrograms per cubic meter.
These tiny particles, which are 30 times smaller than the width of a human hair, pose a serious threat to human health by penetrating deep into the lungs and entering the bloodstream.
At its worst, the AQI in Hanoi surpassed 400, a level classified as hazardous and posing risks even to healthy individuals.
Despite this, Vietnam’s capital attracted more than 25 million people in 2024 and is tipped to exceed that number in 2025.
The spike in pollution has been attributed to several factors: heavy traffic congestion, emissions from coal-powered industries, and the widespread burning of agricultural and household waste. Winter weather patterns, including temperature inversions that trap polluted air close to the ground, have exacerbated the situation.
The air pollution crisis has triggered widespread concern among Hanoi’s residents, with hospitals having reported a surge in respiratory-related illnesses, including asthma, bronchitis, and cardiovascular complications.
Authorities say that vulnerable groups such as children, the elderly, and those with preexisting health conditions are bearing the brunt of the crisis. Many parents have kept children home from school on days with particularly poor air quality, while others have scrambled to purchase air purifiers and high-quality face masks.
Other cities across South East Asia such as Ho Chi Minh City, Phnom Penh, and Bangkok have also experienced severe air quality deterioration in recent weeks. Ho Chi Minh City, for example, ranked as the second-most polluted city globally on several days in January, while Bangkok experienced record-breaking smog levels linked to vehicle emissions and industrial activity.
The Vietnamese government has acknowledged the severity of the crisis and is ramping up efforts to address pollution. Key initiatives include stricter regulations on vehicle emissions, the promotion of electric vehicles (EVs), and curbing industrial pollution.
One of its proposals aims to transition at least 50% of buses and 100% of taxis in Hanoi to electric vehicles by 2030. Additionally, the city has committed to increasing green spaces and improving waste management to reduce the harmful practice of burning garbage.
Hanoi’s air quality crisis underscores the urgent need for international collaboration to combat urban pollution. Experts suggest that while individual countries can implement policies to reduce emissions, cross-border air pollution caused by shared weather systems and regional industrial activity also demands collective solutions.
Global organisations, including the United Nations Environment Programme (UNEP), have called for expanded investment in renewable energy, public transportation, and cleaner industrial practices to address Southeast Asian pollution.