HANOI – Toxic smog has returned to Vietnam’s capital, blanketing the city and prompting authorities to urge residents with respiratory conditions to stay indoors while setting out urgent measures to tackle air pollution.

Hanoi authorities plan to use remote monitoring systems, including security cameras and AI-integrated traffic cameras, to track and clamp down on polluting or expired vehicles, according to a statement on the local government website.

The authorities will also monitor for illegal burning of garbage, straw and agricultural by-products.

Monitoring data shows Hanoi has hit the red “unhealthy” level on the IQAir Index for nine straight days.

The capital has consistently ranked among the world’s ten most polluted cities in recent days and conditions are forecast to deteriorate further.

The capital’s air pollution spikes each winter due to a mix of traffic emissions, industrial and construction dust, and smoke from agricultural burning in surrounding provinces.

Seasonal weather patterns trap these pollutants over the city, creating thick smog and dangerously high PM2.5 levels that pose serious health risks to residents.

All building contractors will need to implement strict dust-control measures, plant more trees, build dust-monitoring systems at all large projects over 10,000 sq m.

Construction projects that do not meet the requirements will be suspended, according to the statement.

Hanoi’s health department has also been urged to advise residents particularly the elderly, children and individuals at risk to limit outdoor activities and wear masks during high air pollution periods, the statement said.

It is also preparing for a possible surge in respiratory cases.

Schools have been told to limit outdoor activities for students when the air quality is at the “poor” level or higher.