Air pollution in Hanoi worsened sharply on Friday, returning to very unhealthy levels after a short improvement, renewing public health concerns and pressure for sustained intervention.
At 8am, the Air Quality Index at the monitoring station outside Hanoi University of Science and Technology on Giai Phong Street reached 228, classified as very unhealthy. The reading had entered this range as early as 3am. Other locations also recorded unhealthy air, including Nhan Chinh Park on Khuat Duy Tien Street with an AQI of 182 and the Nguyen Van Cu Street station with 177.
By 11:30am, Swiss air quality technology company IQAir ranked Hanoi as the world’s fourth most polluted city, with an overall AQI of 193. The city ranked behind Kolkata at 220, Delhi at 211, and Baghdad at 196. Dozens of sites across Hanoi showed very unhealthy air, including Thanh Xuan, Minh Khai, Vinh Tuy, Ha Dong, and Tay Ho.
Real time data on January 9 confirmed persistent pollution. IQAir reported an AQI⁺ of 179 at 5 pm, with PM2.5 concentrations at 96.2 micrograms per cubic metre, around 19.2 times higher than the World Health Organization annual guideline. Other monitoring stations recorded values ranging from 163–231.
PM2.5 was identified as the main pollutant. According to IQAir, morning concentrations peaked at 142.7 micrograms per cubic metre, equivalent to 28.5 times the WHO safe value.
Hanoi had experienced moderate to poor air quality earlier in the week as cold air surges helped disperse dust. Since Thursday, however, stabilised cold air and large day night temperature differences have created temperature inversions that trap pollutants close to the ground.
Very unhealthy air was also recorded in nearby Hung Yen Province, with AQIs of 214 on Nguyen Van Linh Street and 215 at Thai Binh Bridge. Elevated pollution extended to Thai Nguyen Province and Hai Phong City.
The Ministry of Agriculture and Environment’s Department of Environment expects very unhealthy air to persist in Hanoi on Saturday. Vietnam National University Hanoi’s air quality forecasting system predicts the pollution episode will last until 14th January, peaking on 11th January.
Vu Huu Liem, director of the Center for Agricultural, Natural Resources and Environment Monitoring under the National Telecommunications Administration, said high resolution and ultra high resolution satellite imagery is used to monitor pollution hotspots across the city. The system covers construction sites and craft villages and can detect emissions from smokestacks and open burning.
The centre also deploys Matrice 300 RTK unmanned aerial vehicles to conduct detailed real time monitoring at hotspots such as garbage and straw burning sites, supporting inspection and enforcement.
Authorities have prioritised monitoring at 68 construction sites and 14 plastic and steel recycling villages. Construction dust has been linked to failures in complying with material coverage regulations.
Speaking at a government press conference in Hanoi on January 8, Deputy Minister of Agriculture and Environment Phung Duc Tien said air quality remains a serious issue, with PM2.5 pollution requiring urgent attention, particularly in Hanoi and the northern key economic region.
Data from the first nine months of 2025 showed mostly moderate to good air quality, followed by a sharp deterioration from October to December, peaking on December 12. Pollution typically intensifies at night and early morning due to strong temperature inversions, and during peak hours between 9 and 11 am and 3 and 5 pm because of traffic and industrial activity.
Authorities cited unfavourable weather conditions such as fog and prolonged inversions as objective factors, while traffic emissions, construction, road expansion, spontaneous waste burning, and emissions from craft villages and industry were identified as major human driven causes.
The ministry is coordinating with relevant agencies to implement stricter controls, including weekly monitoring reports submitted every Friday for review and reporting to the prime minister. Plans include expanding the monitoring network with rapid sensors in Hanoi and neighbouring provinces, and issuing forecasts and warnings two to three days in advance.
Emergency measures activated in late November include increased street cleaning, stricter construction controls, and bans on open burning. Longer term efforts include amendments to the Law on Environmental Protection, development of inter regional regulations, and strengthening the national steering committee on air pollution remediation.
Investment priorities include a synchronised monitoring network, digital transformation, and development of a national emissions database. Authorities are also promoting public communication, international cooperation, low emission zones, and transitions to greener transport.
Hanoi has reiterated that it will not sacrifice environmental protection for economic growth. Low emission zones are being established as a core emissions control measure under Resolution No. 57/2025/NQ HDND and the 2024 Capital Law.
At a seminar on January 6, Truong Manh Tuan, Deputy Head of the Division of Environmental Quality Management under the Vietnam Environment Agency, warned that PM2.5 pollution during the dry season often exceeds safety limits, posing heightened risks to children, older adults, and people with respiratory or cardiovascular conditions.
The national action plan for 2026 to 2030 aims to reduce PM2.5 levels in Hanoi by 20% by 2030 compared with 2024 levels, targeting concentrations below 40 micrograms per cubic metre. Neighbouring provinces are expected to achieve reductions of more than 10%.
Officials and participants stressed that lasting improvements will depend on long-term coordination between authorities, businesses, and the public.
About the Author
