'API system includes 5 major air pollutants which could cause potential harm to human health should they reach unhealthy levels. The air pollutants included in Malaysia's API are ozone (O), carbon monoxide (CO), nitrogen dioxide (NO), sulphur dioxide (SO) and particulate matter with a diameter of less than 10 micron (PM10). - FAQ section, http://apims.doe.gov.my/v2/faq.html.
While Malaysia is using PM10 in its API, its neighbour Singapore is using PM2.5 instead (particulate matters with size equal or less than 2.5micrometers). PM2.5 is known to be more dangerous since it can travel deeper into our respiratory system (eg. lungs) and PM2.5 is also known to contain higher percentage of hazardous material (eg. heavy metals, toxic organic).
The concentration for PM10 is alsways higher than PM2.5 concentration, since PM10 measures particulates with size less or equal to 10micron which includes particulates of 2.5micron size or less. However when converted into air pollution index, API based on PM2.5 is usually higher than API that is based on PM10. This is due to different breakpoint values used for PM2.5 and PM10, to calculate the index. That's why when 'Good' or 'Moderate' API is given, I do question if the index is correct coz when I gaze outside, I still see the haze.
|Source : Guidelines for the Reporting of Daily Air Quality – the Air Quality Index (AQI), USEPA|
Agak pening jugak lah kalau tengok calculation. Just need to remember that PM2.5 is more dangerous than PM10, hence giving a higher index number. Too bad Malaysia is still measuring the API based on PM10. They can say the API is Good/Moderate but bottom line, trust your eyes & nose too.
'DOE is in the midst of finalising the new Malaysian Air Quality Guidelines to include the standard limit of PM2.5 in the ambient air which based on World Health Organisation (WHO) 2006 Guidelines. Subsequently, we will need to come up with PM2.5 Air Quality Index System and data integration with the existing system in Environmental Data Centre (EDC) prior to including it in API calculation.
- FAQ section, http://apims.doe.gov.my/v2/faq.html.'