Air Quality to be reported hourly instead of 3 hourly; near real-time estimates
Singapore, June 2016 – The National Environment Agency (NEA) has introduced bands and descriptors for the 1-hr concentration readings for fine particulate matter (PM2.5). This will help the public to better interpret the 1-hr PM2.5concentration readings and plan their immediate personal activities.
Since 2014, NEA has been publishing the 1-hr PM2.5concentration readings on an hourly basis for the five regions in Singapore. The 1-hr PM2.5concentration readings are a better indicator of current air quality than the 24-hr Pollutant Standards Index (PSI) and 3-hr PSI readings, especially during periods of haze. This is because the 1-hr PM2.5concentration reading reflects the average concentration of PM2.5, in micrograms per cubic metre (µg/m3), measured in the air over the past 1 hour while the 24-hr and 3-hr PSI are rolling averages of the PSI readings over the past 24 hours and 3 hours respectively.
Although there have been recent studies on sub-daily or shorter PM2.5exposure, the results of these studies, as of now, do not constitute a sufficient evidence-base for the development of health advisories for the 1-hr PM2.5concentration readings. Hence, at this juncture, NEA will only introduce bands, with corresponding descriptors that describe the current air quality, and a general guide for the 1-hr PM2.5concentration readings.
While the 1-hour PM2.5concentration reading can be volatile and tends to fluctuate through the day, especially during periods of transboundary haze, it serves as a useful reference to help the public plan their immediate personal activities.
Phasing out the 3-hr PSI
With the introduction of bands and descriptors for the 1-hr PM2.5concentration readings, the public will be able to better interpret the 1-hr PM2.5concentration reading, which is a near real-time indicator of the current air quality. Hence, the 3-hr PSI will no longer be relevant and NEA will phase it out before the end of 2016.
Changes to the haze microsite and myENV app
NEA will be providing additional information on the haze microsite (www.haze.gov.sg) and myENV app, to include the new bands and descriptors.
Since 2013, NEA has been publishing a 24-hr PSI daily forecast during periods of haze on the homepage of the haze microsite. The 24-hr PSI forecast is the forecast of the 24-hr PSI over the next 24 hours. It is based on NEA’s expectations about the air quality and informs the corresponding health advisory. This forecast will continue to be used to advise major decisions, e.g. school closure. To help more members of the public receive the forecast, NEA will be incorporating the 24-hr PSI daily forecast in the myENV app during periods of haze.
Singapore’s air quality readings are taken from 22 air quality monitoring stations across the island. Members of the public can visit our NEA website (www.nea.gov.sg), the haze microsite (www.haze.gov.sg), follow us on NEA Facebook (www.facebook.com/NEASingapore) and NEA Twitter (@NEAsg), or download the myENV app.
 PM2.5 is the dominant air pollutant in smoke haze.
Bands and Descriptors for the 1-hr PM2.5concentration readings
The 1-hr PM2.5concentration reading reflects the average concentration of PM2.5, in micrograms per cubic metre (µg/m3), measured in the air over the past 1 hour.