As planned, Hanoi will add 33 air monitoring stations next year, raising the total to 44. It will also require industrial parks and factories across the city to install their own stations.

All data collected from the stations will go to the environment department, which will make the air quality predictions, Luu Thi Thanh Chi, deputy head of the department, said at a conference on air pollution held in Hanoi Friday.

So far, the department has provided air quality information on the website moitruongthudo.vn, with updates of the air quality index every day and in coming days, the index is expected to be updated every hour.

The air quality in Hanoi has gone from bad to worse in recent weeks with the capital consistently topping the list of cities with the worst air quality in the world among more than 10,000 monitored by the app IQAir AirVisual.

The city of 7.5 million has around seven million vehicles, with two million more coming in from other places every day, creating severe traffic congestion during rush hour.

Mai Trong Thai, head of Hanoi's environment department, said they were working with the World Bank (WB) to identify the main sources of air pollution in the city, and will announce the results next May.

World Bank official Nguyen Thi Le Thu said the organization was studying air pollution causes in several cities of seven nations, including China, Egypt, South Africa and Vietnam.

In Vietnam, besides Hanoi, the bank is conducting studies in the two northern provinces of Hung Yen and Bac Ninh. Based on its findings, it hopes to suggest solutions to help the localities improve their air quality.

"The project is expected to help Hanoi find out where the fine dust comes from. We have been talking about the busy traffic, factories, the burning of straw on the city's outskirts, the emissions from craft villages, but specific figures are needed to identify the main sources of the PM2.5," she said.

The PM2.5 particulate level in Hanoi reached a five-year high last month and environment officials urged residents to limit outdoor activities.

Between September 12 and 30, PM2.5 levels – described as superfine particles with 3 percent the diameter of a human hair – were consistently above 50 μg/m3, according to a report from the Ministry of Natural Resources and Environment.

Vietnamese standards prescribe safe PM2.5 limits of 50 µg/m3 for 24 hours and 25 µg/m3 over a year, opposed to corresponding figures of 25 and 10 by the World Health Organization (WHO).

PM2.5 particles are discharged by vehicles, industry and natural sources like dust and can easily pass through lung tissue and be absorbed into the bloodstream, causing adverse health effects.

Hoang Duong Tung, president of the Vietnam Clean Air Partnership (VCAP), said aside from looking for the main pollution sources, Hanoi should devise timely solutions to deal with the ongoing situation.

Many countries in the world have been collaborating with motorbike manufacturers and set up systems to check their emissions. Motorbikes with emissions beyond prescribed levels are banned till they meet set standards, he said. Many countries also have marked out areas where all vehicles are required to meet certain emissions standards.

Hanoi needs to apply such measures, he noted.

WHO representative Kidong Park said Hanoi should learn from Beijing measures it can take to improve air quality, including strengthening the air monitoring system and improving citizens access to the mainstream information sources, and applying emergency measures when the air pollution index exceeds thresholds in specific areas.

Chronic air pollution can trigger strokes, heart attacks and chronic pulmonary obstructions as also affect the reproductive system. In 2016, an estimated 60,000 Vietnamese citizens died of diseases related to air pollution, according to WHO.