The air pollutant index (API) information provided by the Department of Environment complies with international standards and protocol, the department says.
This comes after public insistence that the published API measures do not match actual conditions yesterday, when thick haze engulfed major cities nationwide and poor visibility forced closure of an airport.
In a statement, the DOE said API readings are not visibility measures.
It said visibility readings are measured in real time while API readings are measure of dust particulate matter smaller than 10 microns (PM10), in a span of 24 hours.
Visibility is measured by the Meteeorological Department in shorter time frames, it said.
"Therefore, the API would take time to show an unhealthy reading because it is an average measure of PM10 in 24 hours," it said in the statement issued early this morning.
PKR's Kelana Jaya MP Wong Chen (photo) in a separate statement today urged the government to measure particulate matter of 2.5 microns (PM2.5) instead of PM10, like Singapore and Indonesia.
By using PM10, he said, Malaysia is giving an "illusory picture of the state of our nation's air quality".
He also claimed that DOE has the PM2.5 data from its Putrajaya, Banting, Cheras, Langkawi and Kuching stations.
Earlier media reports note that DOE plans to implement the PM2.5 measure next year.
The haze scourge returned after a brief respite last week to cloak Klang Valley in unhealthy levels marking 201 to 300 on the API this morning.
Malacca, Negri Sembilan, Perak and Sarawak continued to suffer unhealthy readings, forcing hundreds of schools to close tomorrow, while Johor levels have dropped back to moderate levels.
An API reading of 0 to 50 indicates good air quality; 51 to 100, moderate; 101 to 200, unhealthy; 201 to 300, very unhealthy and 300 and above, hazardous.
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Worsening haze shuts down schools, flights
