PSI readings in Singapore edges up, peaking at 87

Singapore's 3-hour Pollutant Standards Index (PSI) reached this year's highest level at 8:00 p.m. Tuesday evening with a reading of 87, and Singaporeans were worried about whether haze is back.

The readings of 3-hour PSI had been rising steadily throughout the day, from 67 to 87, and it went down to 83 at 10:00 p.m. Tuesday evening. Although the readings of 24-hour PSI were still within the Moderate range, many Twitter users reported the smell of "haze" in the air in the evening.

"Is the haze back?" came crossed the minds of many people in Singapore when the skies turned grey with burning smell. The PSI readings have been from 40 to 60 in recent months, and this is the first noticeable spike in 2016.

According to the Straits Times, experts said it is unlikely to have been caused by transboundary haze, which crouched over the city state for a long period of time last year. Prevailing winds are expected to be from the north or north-west, while haze is generally blown in by south-westerly winds.

"Due to the transient nature of such smells, it is difficult to identify the cause or source of the smells," said National Environment Agency. The authority also added there is no correlation between PSI readings and burning smells in the air. Endit