With the haze officially back and a part of our daily lives, I’m sure that many of us would want to keep ourselves updated on the Pollutant Standards Index (PSI) readings.
The PSI level is constantly fluctuating, and it has been hovering between the “moderate” and “unhealthy” ranges for the past few days.
However, since there so many websites and platforms that tell us these readings every day, how do we know which ones are the most accurate?
NEA Addresses Why Other Websites’ Readings Are Inaccurate
Sometimes, the readings given by alternative air quality reading websites are higher than the one given by The National Environment Agency (NEA) for the same time period, and obviously this can be really confusing.
But NEA is here to clear all your confusion away, and also reveal why those websites’ PSI readings are inaccurate.
Time to spill some tea.
For instance, one popular website measuring air quality is called aqicn.org.
Dr Khairunnisa Yahya, a senior scientific officer who works at the Pollution Control Department at NEA, said in an interview with TODAYonline that the website uses the incorrect Particulate Matter 2.5 (PM2.5) reading to derive its final air quality index.
The website uses the hourly PM2.5 readings instead of the 24-hour average PM2.5 readings.
Hourly PM2.5 Readings Are Not As Meaningful
“You’re not supposed to use the 1-hour PM2.5 reading. If you took the 1-hour PM2.5, compared to the 24-hour average PM2.5 readings… of course it will be higher,” said Dr Khairunnisa.
The Air Quality Index (AQI) by the United States Environmental Protection Agency (EPA) has advised that the average 24-hour PM2.5 readings should be used when measuring air quality.
Dr Khairunnisa went on to explain that the hourly PM2.5 readings may not be that meaningful, as scientific findings on the effects of particulate matter on a person’s health are based on 24-hour exposure to PM2.5.
Other Alternate Readings Available
Apart from aqicn.org, there are also other websites and applications with air quality readings available, such as Originally US, which is a Singapore mobile app development agency founded in 2014.
It posted its own version of the “No bullshit PSI readings” to its Facebook page on Saturday, 14 September.
Their webpage reads:
“We have created what we think is a right implementation of NEA’s official PSI formula on haze.gov.sg to deduce the actual, hourly PSI measurements from hourly PM2.5 readings.”
However, NEA has not responded directly to the accuracy of Originally US’s readings.
NEA’s Has 22 Air Monitoring Stations
NEA has a total of 22 air quality monitoring stations, which are spread throughout Singapore. Each of these stations is equipped with six sensors, and the data from these stations are used to calculate Singapore’s 24-hour PSI.
“We would advise the public to look at our PSI readings, because those readings are based on measurements from our air monitoring stations,” said Dr Khairunnisa.
She also said that other sites may be using other devices, like “low-cost air-quality sensors that can be bought off the shelf”. Thus, their readings might not be as accurate as the ones from NEA, who’s sensors adhere to the US EPA standards.
So now we know that it’s best to just stick with the updates provided by NEA after all.
NEA provides both the 24-hour PSI and 1-hour PM2.5 on their website, and you can view them by clicking here.