Stations report drop in air pollution during lockdown 

Choki Wangmo 

Confinement measures imposed to slow the spread of the Covid-19 pandemic last month have resulted in an unprecedented fall in air pollutants across the country.

All four air quality monitoring stations reported about 50 percent drop in the particulate matter during the nationwide lockdown. The records with the National Environment Commission (NEC) showed comparative improvement in the air quality this year.

In Thimphu, the lowest concentration was recorded on August 17 where the particulate matter (PM10) level was only 2.08 µg/m3 which is the lowest recorded so far for PM10. Last year, the lowest concentration was recorded at 3.62 µg/m3.

The concentration level decreased drastically within a few days of the nationwide lockdown, said an official with the Climate Change Division in NEC.

“The PM10 concentration for 2020 was observed to have decreased drastically in comparison to 2019,” she said.

Particulate Matter is one of the most important causes of health impacts in urban areas across the world. The concentration of particulate matter less than 10 µm in diameter (PM10) is the parameter measured and monitored through all four NEC stations.

In Rinchending, although the PM10 concentration level for April 2020 was higher than that of 2019 by 15 percent, in May, the concentration dropped by more than 50 percent compared to 2019.

The concentration in June and July was similar in both years but the concentration level dropped almost by 50 percent in August this year, the official said.  The PM10 concentration for 2020 was observed to have decreased drastically in comparison to 2019.

In Dewathang, the highest concentration was observed in December 2019 and February 2019 with concentration levels exceeding 111.93 µg/m3 and 110.05 µg/m3 respectively compared to the permissible limit of 100 µg/m3 on a 24-hour average basis.

While the PM10 concentrations for February, March, and April were lower compared to 2019, the PM10 concentration in May and June this year showed an increase in the concentration by 30 percent and 24 percent compared to 2019, before drastically dropping in July 2020.

The data for August, however, couldn’t be obtained due to lockdown in Samdrupjongkhar during the data collection period.

Air pollution in Bhutan is still largely particulate matter and comes from a variety of sources such as vehicular emissions, space heating using wood and other fuels, forest fires, and open burning of agricultural debris, among others.

The current Ambient Air Quality Standard 2020 sets the permissible limit of total suspended particulate matter of PM10 in a day at 500 µg/m3 in an industrial area, 200 µg/m3 in a mixed area, and 100 µg/m3 in a sensitive area.

“Mixed Area” refers to areas where residential and/or commercial activities take place. And similarly, “Sensitive Area” refers to areas where there are places such as hospitals, schools and sensitive ecosystems.

The overall concentration of PM10 in Bhutan is within the permissible limit of the ambient air quality standard of 100 µg/m3 on a 24-hour average basis.

The first international day of clean air for blue skies was celebrated on September 7 to boost cooperation to tackle air pollution and provide clean air for all.

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