A view shows the city of Hanoi amid air pollution, Vietnam, December 11, 2025. REUTERS/Thinh Nguyen
HANOI, Dec 11 (Reuters) - Industrial plants in the Vietnamese capital of Hanoi have come under renewed pressure to scale back their operations as authorities respond to a week of heavy and hazardous smog in the city.
Vietnam's Ministry of Health earlier this week urged power, steel and chemical plants to cut output when the air quality index exceeds 200. The index gauges the volumes of hazardous small particles known as PM2.5 that are in the air.
The AQI hit 243 midday on Thursday, putting Hanoi fourth on the list of the world's most-polluted cities, according to AirVisual, which provides independent global air pollution information via a phone app.
The city has topped the list on a number of occasions this week, according to the app, a position it also held in January.
The Southeast Asian country, a regional manufacturing hub which is urbanising rapidly, has been suffering from severe air pollution for years, especially in Hanoi.
"My eyes are itchy, and there's always a blanket of smog that blocks my vision," said Hanoi resident Pham Thu Giang, 30. "I have to wear a mask all the time."
The authorities have identified transportation, industrial production, construction activities and the burning of garbage and agricultural residue as the main sources of air pollution in the city.
"Gasoline-powered motorbikes are used widely in Hanoi, making them a major source of air pollution," Le Thanh Thuy, an official of the city's department of agriculture and environment, told local media on Thursday.
The city will impose partial bans on gasoline-powered motorbikes in downtown areas from mid-2026 and will gradually expand the ban thereafter to fossil-fuel-powered cars.
"The current air conditions are very dangerous for the capital Hanoi," said 75-year old resident Luong Van Toi. "I feel very tired."
If Hanoi's AQI is converted into actual PM2.5 concentrations, the pollution this week could be as much as 50 times the 5-microgram/cu m level recommended by the World Health Organization.
(Reporting by Thinh Nguyen; Writing by Khanh Vu; Editing by David Stanway)
