Some Singaporeans might have noticed the poorer air quality in the past two days.
have actually noticed a bit of haze here in Singapore over the last few days— Andrew Janes (@AndrewJanes4) February 23, 2021
On Feb. 27 evening, the National Environment Agency also reported that the 24-hour Pollutant Standards Index (PSI) was at the "Unhealthy" level.
Is Haze back in Singapore? pic.twitter.com/Af2k6dAfOH— Kallang Wave (@Kallang22) February 27, 2021
In particular, the 24-hour PSI level was above 100 in the north at 7pm.
Spike in ozone
The 24-hour PSI is computed based on these six air pollutants: PM2.5, PM10, ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide.
PM2.5 is the dominant pollutant during haze episodes.
According to NEA's website, the reason behind the spike in the PSI level is likely due to an increase in ozone during that period.
There is no anomaly in the readings of other pollutants including PM 2.5 and PM10 and therefore the drop in air quality is unlikely due to the forest fires in the region.
What is ozone?
Ozone at ground level is formed when pollutants (hydrocarbons as well as nitric oxide and nitrogen dioxide) emitted by cars, refineries, chemical plants, and other sources react chemically in the presence of sunlight.
Ozone can reach unhealthy levels on hot days in urban environments.
Mothership has reached out to NEA for comments.
Top image via Unsplash by Christoph Theisinger