Singaporeans should focus on the 24-hour Pollutant Standards Index (PSI) because that is a better indicator of the haze's health impact, Second Minister for the Environment and Water Resources Grace Fu urged at a briefing on Friday.
She acknowledged that people were still concerned about the higher, three-hourly PSI which hit a record 401 at noon on Friday. But she said the haze's impact also depends on how long people are exposed to it.
"The 24-hour measurements are a better reflection of the total exposure of an individual to the particulate matter. It is important for the public... not to be too overly concerned with the three-hour PSI which may show spikes and drops from time to time."
From Friday, the NEA has also issued a rolling 24-hour PSI reading every hour on its website, in addition to the three-hourly updates, to give a better sense of the likely impact on people's health.
The 24-hour PSI is averaged form readings taken over the past 24 hours. The 3-hour PSI, which is averaged from readings in the past three hours, was introduced in 1997 to give people more current information.