Hourly PSI readings would allow for better decision-making

Amid the annual haze, I would like to again strongly make the case for the National Environment Agency (NEA) to provide hourly Pollutant Standards Index (PSI) readings instead of three-hour averages.

Singapore is a small country and a slight shift in prevailing winds can cause sudden significant changes in air quality. With a three-hour-average PSI, lower PSI levels for the earlier two hours can lower the reading when the haze has already reached a hazardous level in the third hour.

The NEA’s FAQs on PSI webpage states that its health advisory is based on the 24-hour PSI as it is a “better reflection of the total exposure”, and health effects have been mostly studied based on this measure. In comparison, the three-hour PSI is only “an indicative measure” that the public may use “to make adjustments to their daily activities if they wish to do so”.

I understand that public health planning is more effectively done on a daily, 24-hour basis. However, logically and given a choice, most people would refer to a shorter time frame to avoid exposure to the worst hours of the haze.

While the use of three-hour averages may moderate PSI readings and prevent undue panic, it is irresponsible not to provide a more accurate hourly measure for Singaporeans to protect themselves, especially when the NEA has the data.

This is particularly incongruous given that the hourly PM2.5 readings are available on the NEA website, which are equally “highly variable when the wind drives smoke haze from place to place” as stated by the NEA.

Furthermore, there exist websites (such as http://by.originally.us/psi/real) that calculate hourly PSI readings from the official three-hour averages.

Such websites have received positive coverage on new media outlets, increasing their reach.

Rather than allowing questionable sources to provide possibly inaccurate information that may cause the very panic we want to avoid, the NEA would do better by releasing the official hourly readings.

Schools, the Singapore Armed Forces and some companies regulate activities based on 24-hour PSI readings, but hourly readings would also provide teachers, commanders and employers with additional information with which to make decisions on the ground regarding outdoor activities, to minimise unnecessary exposure.

Such information is also invaluable for those working in essential services, such as security officers at our land checkpoints and key installations.

Thus, I sincerely hope the NEA would reconsider its stand on hourly PSI readings.