The hailstorm which hit certain parts of western Singapore is not toxic, a National Environment Agency (NEA) spokesman assured in a media conference.
The agency added that hail is caused by supercooled water droplets freezing on contact with particles in the air, such as dust, during a thunderstorm, and PM2.5 and PM10 are only hazardous when inhaled. NEA was unable to confirm if the hailstorm was brought about by the haze.
The last reported hailstorm in Singapore took place about five years ago, on 27 March 2008.
Residents in western Singapore reported seeing hail falling from the skies at about 3pm on Tuesday.
Heavy rain, accompanied by gusty winds, started around 3pm in areas including Jurong and Bukit Batok – a welcome respite for Singaporeans who only recently endured over a week of record-breaking haze caused by forest fires in Indonesia.
Musician Laura Tang, 24, was near West Coast Park when she noticed the hail.
"The wind suddenly turned very cold, and these crystal-like stones started raining down," she said.
"It was very frightening. I could not believe my eyes," she added.
Ms Caydence Woo, 24, said the substance felt like "very sharp droplets that were a little prickly, like sand, when it landed on my hand".
The banking executive was on her way to Clementi Mall when she noticed the sound of droplets bouncing off her umbrella was exceptionally loud, and decided to put her hand out to feel them.
“The droplets also looked weird. They were coming down in straight, solid lines, instead of one by one,” she said.