Vehicles are stuck in a traffic jam in Hanoi's Nguyen Trai Street, May 11, 2020.
Photo by VnExpress/Ngoc Thanh. 

Hanoi had the most polluted air in Vietnam last month, with the highest PM2.5 levels and AQI, a recent government report showed. 

The report by the Vietnam Environment Administration (VEA) published on Wednesday showed that its PM2.5 level was 22-48 μg/m3, while for Ho Chi Minh City it was 8-30 μg/m3.

The capital recorded AQI of 45-92 last month while HCMC recorded between 18 and 61, the report showed.

The report used data collected from several stations in Hanoi, HCMC, Ha Long, Viet Tri in the northern province of Phu Tho, Da Nang, Hue, and Nha Trang.

PM2.5, also described as super fine particles, is a fraction of the width of a human hair and comes from vehicles and factories and natural sources like dust.

The World Health Organization (WHO) Air Quality Guideline recommends an annual mean exposure threshold of 10 μg/m3 to minimize health risks.

Air Quality Index (AQI) is used by government agencies to tell the public how polluted the air is or could be. AQI levels above 100 are considered unhealthy.

Hanoi’s AQI levels showed that the city enjoyed either good or average air quality for around 90 percent of May, though it varied in different parts.

Vietnam as a whole, however, enjoyed better air quality last month compared to April, with lower levels of PM2.5, according to the report.

VEA cited the beginning of the rainy season as a factor affecting air quality in May.

Vietnam ranked fourth in the number of pollution-linked deaths in the Western Pacific region, the Pollution and Health Metrics report by the Global Alliance on Health and Pollution said last December.

An estimated 71,365 Vietnamese lost their lives to pollution in 2017, the latest year for which data was available, according to the report. The number included 50,232 killed by air pollution.

The World Health Organization (WHO) said that more than 60,000 deaths in 2016 from heart disease, stroke, lung cancer, chronic obstructive pulmonary disease, and pneumonia in Vietnam were linked to air pollution.