|A street in downtown HCMC is empty on the second day of the nationwide social distancing campaign, April 2, 2020. Photo by VnExpress/Quynh Tran.
The air quality from March 20 to April 10, which partly coincided with the nationwide social distancing campaign to curb the spread of the COVID-19 pandemic, saw an improvement compared to January and February, VEA said in a report published recently.
In Saigon, for instance, the daily PM2.5 levels from March 20 to April 10 was consistently below 20 μg/m3 on average, a stark reduction from January or February, when they were 40-60 μg/m3 on average, it said.
PM2.5, also described as super fine particles, is a fraction of the width of a human hair, which is released from vehicles, industry 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.
In Hanoi the PM2.5 levels in the first quarter were lower on average than in previous months too, VEA said.
In January and February, the air quality in Hanoi was bad around half of the time, but that did not happen any day in March, the administration said.
"It shows that sources of emission like traffic and production had considerably influenced urban air quality," the administration said.
Other air quality metrics, including the levels of carbon monoxide (CO), have also seen improvements. For example, average CO levels in Hanoi from April 1 to 10, when the nationwide social distancing campaign was on, fell remarkably from the first quarter.
Daily CO levels were on average 500-1,300 μg/m3, whereas in January-March it rose to 2,000 μg/m3 at certain times.
"Social distancing measures, which led to reduced or suspended production, traffic and construction, helped improve air quality," the report concluded.
The campaign required people to stay at home and prohibited gatherings of more than two people.
It was first introduced from April 1 to 15, and has since been extended to at least April 22 in 12 localities with a high risk of COVID-19 infection, including Hanoi and Ho Chi Minh City.
In Vietnam there have been 268 COVID-19 patients so far, including 67 currently in hospital.
The pandemic has spread to 210 countries and territories and claimed more than 160,700 lives.