One worker dead, two Malaysians in ICU after inhaling poisonous fumes while cleaning Singapore Waterworks tank

SINGAPORE: A 40-year-old worker has died after inhaling a poisonous gas while carrying out routine tank cleaning at national water agency PUB’s Choa Chu Kang Waterworks on Thursday (May 23).

The worker – an Indian national – was one of three men aged between 24 and 40 who had collapsed and were found unconscious at the plant at about 11.15am.

All three were taken to hospital unconscious, where the worker died. The two surviving workers are in the intensive care unit at Ng Teng Fong General Hospital, said PUB in a statement.

The two men are Malaysians who are aged 24 and 39, and employed as general workers, said the Ministry of Manpower (MOM) in a statement.

MOM added that the man who died was a cleaning operations manager and, along with the older Malaysian, was employed by Supersonic Maintenance Services. The younger Malaysian works for Stargroup Est.

The ministry said it is investigating and has instructed PUB to stop all tank cleaning work.

PUB, in a statement, said early investigations suggest that the workers had inhaled hydrogen sulphide – a gas produced from sludge, which is a by-product of the water treatment process.

Cleaning works are carried out at the plant routinely once every three months.

In response to queries, the Singapore Civil Defence Force (SCDF) said it was alerted to a hazardous material (hazmat) incident at 51 Nanyang Drive at about 11.25am.

Firefighters and hazmat specialists in personal protective equipment used two water jets to disperse the poisonous gas.

After about an hour of “vapour dispersion”, there was no more hydrogen sulphide detected in the plant, said SCDF. It added that cardiopulmonary resuscitation, or CPR, was performed on one of the workers on the way to hospital.

The police have ruled out foul play.

Hydrogen sulphide is a colourless gas that gives off the odour of rotten eggs, according to an entry on the United States National Institute for Occupational Safety and Health (Niosh) website.

Exposure to the gas can cause irritation to the eyes and respiratory system, and can lead to issues like falling into a coma.

Workers in wastewater treatment industries are a group at risk, the Niosh website states.

MOM said that as a general safety measure, proper ventilation must be provided to prevent the accumulation of toxic vapours.

Workers should also be equipped with gas monitoring devices and personal protective equipment for their safety, it added.

Choa Chu Kang Waterworks is a key plank in Singapore’s goal of achieving water security, and supplies 80 million gallons of safe drinking water to the western part of the island, said an environmental impact assessment published in 2022.

Upgrading of the plant began in 2022, and the works are slated to be completed by 2026.

PUB said it has called a safety time-out for similar operations in confined spaces and is reviewing the associated safety measures.

It said: “Safety and health at all our workplaces are of utmost importance to PUB. We will cooperate fully with the investigation.”

The agency expressed its condolences to the family of the worker who died and said it was in touch with its contractors and would provide support to the workers’ family members.

Responding to queries, PUB said this is the first time such an incident has occurred. – The Straits Times/ANN