The chemical stench that cloaked the island on Monday came from the industrial town of Pasir Gudang in Johor, investigations have revealed.
The National Environment Agency (NEA) said yesterday that its Malaysian counterpart, the Department of Environment (DOE), had identified the source of the smell, and would be taking action .
"The DOE has deployed resources in identifying the source of the smell. It has traced the source to an industrial facility in Pasir Gudang, and is taking action against the operator," it said. The Malaysian authorities were not immediately available to comment on which facility was at fault, or the composition of the gas.
NEA stressed yesterday that air quality in Singapore has remained at safe levels since Monday, and it will continue to monitor the situation.
A large zone in the 311 sq km town of Pasir Gudang is dedicated to heavy industries, and fumes and pollutants have drifted to Punggol in past incidents. The industrial estate, established in the 1990s, is a little more than 1.5 km across the Strait of Johor from Punggol, and controlled burning to get rid of waste gases is a common occurrence there. The town is home to a port, power station and petrochemical companies, as well as those dealing with edible oils, steel and fertiliser.
On Monday, complaints poured in from residents in Sengkang and Punggol, and later in Ang Mo Kio, Yishun, Seletar and Bishan, about an acrid, chemical smell. The NEA said its officers and those from the Singapore Civil Defence Force were sent to affected areas to investigate and test air quality. Checks of factories in affected areas revealed no abnormal operations or any other possible sources of gas and chemical leaks.
Light winds over the northern half of Singapore at the time might have led to an accumulation and slow dispersion of smells, it added.
While those affected were afraid that the gas was toxic, the NEA assured the public that air monitoring stations here detected only low and safe levels of volatile organic compounds (VOCs) in the air. VOCs are chemical compounds that easily enter the air. "They are numerous, varied and commonly present, and each individual's reaction to VOCs may vary," the NEA said.