The increasing amount of airborne fine dust has been posing public health risks to urbanites in Vietnam’s southern and northern metropolises of Hanoi and Ho Chi Minh City in recent times, experts have warned.
A number of Hanoi people experienced dust-related breathing difficulty and coughing when a high traffic volume was noticed last month, resulting in a concentration of tiny dust particles that was at some points double Vietnam’s maximum safety limit and exceeded the WHO ceiling by four times.
A Hanoi resident said she and her colleagues had to close all company doors and windows, filled every opening in the doors and purchased an air purifier to keep the pollution at bay.
Dust was kicked up by running vehicles and gathered in thick layers on the façade of the houses along an under-construction overpass on Pham Van Dong Street in the capital city.
The road is notorious for its poor air quality as it has always ranked first in terms of air pollution across Hanoi, according to the municipal natural resource and environment department.
The capital’s air quality had declined distinctively within the six days of late January, with a number of locations under air pollution observation categorized as ‘bad’ and ‘very bad’ – the lowest levels.
Particulate pollution is also worrisome in Ho Chi Minh City even though it is not as severe as in Hanoi.
“The two metropolises are facing dust pollution as the concentration of particulate matter is still high,” Nguyen Thi Anh Thu, a worker at Vietnamese non-profit Green Innovation and Development Center.
Particulate matter, or PM, is a mixture of solid particles and liquid droplets suspended in the air, many of which are hazardous. PM is reportedly the deadliest form of air pollution due to their ability to penetrate deep into the lungs and blood streams unfiltered.
Thu attributed the high concentration of PM in Hanoi in part to the currently rising amount of road traffic and construction.
Another cause, she said, is the presence of numerous high-rise buildings and dust carried by winds from neighboring industrial factory areas and from other countries.
|Workers repair a sidewalk in Hanoi, Vietnam, in late 2018. Photo: X. Long / Tuoi Tre|
A point in this view was echoed by Hoang Duong Tung, director of the Vietnam Clean Air Partnership, who said Hanoi's air quality plummeted after the number of vehicles moving there surged in January.
Playing a major role in the pollution, Tung underlined, was a phenomenon called inversion, during which warmer air stays above cooler air.
This is the reverse of the normal change pattern where air temperature decreases commensurately with a rise in altitude.
“Inversion traps pollutants close to the ground, causing their concentration to grow above cities,” he said.
He stressed airborne PM2.5, tiny dust particles smaller than 2.5 micrometers in diameter, about one-thirtieth the diameter of a human hair, can pass completely unobstructed to the lungs.
It can cause deadly conditions such as cancer and respiratory and cardiovascular diseases, he said, adding this type of particulate matter comes from carbon dioxide, sulphur, nitrogen and metal chemical compounds.
South Korean suffered a similar particulate pollution but quickly put stringent measures in place whenever the concentration of minuscule dust reached 50 milligrams per cubic meter.
But authorities in Vietnam have been tardy in solving the problem over the past three years, when air pollution has become a real headache.