SINGAPORE - A strong burning smell detected in eastern Singapore on Thursday evening was likely caused by unusual industrial activity or the burning of rubbish, a research scientist told The Straits Times on Friday.
Residents of Pasir Ris, Tampines and Bedok had complained of the stench, which some described as being like burning plastic.
But research scientist Erik Velasco of the Singapore-MIT Alliance for Research and Technology's Centre for Environmental Sensing and Modelling ruled out haze as a possible cause, saying it was an "isolated event".
"The smoke-haze from fires blanketed, in major or minor proportion, the whole island and not only one region like in this case," he explained.
He believed that the smell could have been caused by the burning of rubbish or unusual industrial activity, such as illegally using material like old tyres, plastic bottles and oil for electric transformers as fuel.
"By 11 am (on Friday), the PM2.5 (a type of pollutant particle) concentration in the east had dropped to typical levels," he said. "However, if the spike on PM2.5 and bad smell occurs again, the authorities will have to investigate the origin."
The National Environment Agency (NEA) said on Friday that it had contacted its Malaysian counterparts to enquire if any changes have been observed in the air quality in Johor. It added that the Pollutant Standards Index (PSI) - a measure of air quality here - has remained in the moderate range.
"NEA will continue to monitor the air quality readings and notify the public if there are any changes to the PSI," a spokesman said. The Singapore Civil Defence Force (SCDF) also confirmed that there had been no fires reported in the affected areas.
At 9pm on Thursday, the east had a PM2.5 reading of 44, while the north, west and central Singapore hovered at 16. The south had registered a reading of 5.
PM2.5 dropped to 24 in the east at noon on Friday. That hour, the rest of Singapore registered readings ranging from 21 (north) to 34 (south and west). And as of 5pm on Friday, the hourly PM2.5 readings stabilised in the 'good' range across Singapore.
Dr Velasco said the PM2.5 concentration spike in the east is likely to be a "very local emission source" and not caused by wildfires in neighbouring islands.