Smoke is emitted from a factory chimney in Hanoi, March 10, 2021.
Photo by VnExpress/Ngoc Thanh.
 

Air quality in the Vietnamese capital Hanoi improved in 2020 but was still the 12th worst among cities in the world. 

Its average annual PM2.5 concentration improved after worsening for three straight years, according to the 2020 World Air Quality Report published by IQAir on Tuesday.

The report by the Swiss air quality technology and monitoring company said in 2020 the average pollution exposure in Vietnam fell by 18 percent from 2019 levels.

Strict measures to reduce the spread of Covid-19, including mass quarantines, a one-month nationwide social distancing and restrictions on mass gatherings and mobility contributed to an 8 percent reduction in PM2.5 in Hanoi, it said.

Favorable meteorological conditions accounted for the remaining 10 percent reduction.

However, in the world capital cities ranking based on descending order of annual average PM2.5 concentration, Hanoi was in 12th place.

The city's PM2.5 concentration of 37.9 μg/m³ remained nearly at four times the World Health Organization (WHO) target for annual exposure (10 μg/m³).

Fine particulate matter (PM2.5) is defined as ambient airborne particulates that measure up to 2.5 microns in size, just a fraction of the width of a human hair. The microscopic size allows these particles to be absorbed deep into the bloodstream upon inhalation, potentially causing health effects like asthma, lung cancer, and heart disease. Exposure to PM2.5 has been linked to negative health effects like cardiovascular disease, respiratory illness, and premature mortality.

At a regional level, the IQAir report said Southeast Asia faces air pollution challenges largely stemming from rapid population growth and economic development.

Its energy demand has increased sharply as a result, with electricity demand growing at around 6 percent a year. Many countries in the region continue to lack the equipment and expertise to monitor and report air pollution.

The region mostly relies on fossil fuels for energy, with oil being the leading source and coal the fastest growing.

PM2.5 emission sources in Southeast Asia vary by country and environment. On a positive note, 70 percent of cities in Southeast Asia enjoyed improved air quality in 2020.

PM2.5 concentration in Southeast Asian cities in 2020. Graphics by IQAir.

The report said while gains in air quality monitoring have helped raise awareness, most cities still lack public real-time data. In rural areas, the impact of open burning of rice straw and other materials for heating and cooking remains largely unmitigated.

Rapid urbanization and a growing economy also contribute to ambient PM2.5 levels. Without additional policy measures, PM2.5 concentrations in Vietnamese cities could increase by as much as 20-30 percent by 2030, it said.

The report made use of data from more than 15,000 ground-based monitoring stations in 106 countries.

Globally, Delhi of India, Dhaka (Bangladesh) and Ulaanbaatar (Mongolia) had the worst air quality last year, while Helsinki (Finland), Stockholm (Sweden) and Charlotte Amalie (U.S. Virgin Islands) were the cleanest.

Frank Hammes, CEO of IQAir, said: "The year 2020 brought an unexpected dip in air pollution. In 2021 we will likely see an increase in air pollution due to human activity.

"We hope this report will highlight that urgent action is both possible and necessary to combat air pollution, which remains the world's greatest environmental health threat."