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Mythbuster on air quality reporting in Malaysia and Singapore

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Picture is sourced from

It’s interesting and perplexing to note that air quality index in Johor Baru is moderate yellow alert while Singapore is unhealthy orange alert on 23 September 2015 from the information published at (

The narrow Tebrau Strait should not be a physical barrier for air current flow in the atmosphere between Johor Baru and Singapore. Do not be misled to believe that air quality in Johor Baru is better than Singapore on that day.

The difference in readings and alert flags is mainly due to the different methodology used by both countries.

PM2.5 is more critical in air quality measurement

Singapore is using PSI (The Pollutant Standards Index) to issue air quality warning or alert to public members. The PSI is based on a scale devised by the United States Environmental Protection Agency (USEPA) which included fine particulate matter (PM2.5) since 1 April 2014.

Singapore PSI is taking into account PM2.5 particulates while Malaysia AQI (a.k.a API) is only measuring PM10 particulates. PM2.5 particulates (<2.5 micron) are more harmful than PM10 particulates (<10 micron) for their smaller size which can go deeper and absorb into […]