Clarification: A picture of fire damage at a factory in Pasir Gudang Industrial Park, which was used with this report earlier, has been replaced. The picture is not related to this report.
ISKANDAR PUTERI: An increase in Methyl Mercaptan readings due to fumes from burnt chemical containers has been identified as the source of air pollution that affected 24 students at SK Sungai Tiram in Ulu Tiram near here, today.
Methyl mercaptan known as methanethiol, is a toxic, extremely flammable, colourless gas with a smell similar to rotten cabbage.
The Occupational Safety and Health Administration (OSHA) permissible exposure limit of methanethiol is 10 parts per million (ppm), while the reading recorded was 50ppm.
The Hazardous Material Unit (Hazmat) and Johor Department of Environment (DoE) officers conducted an intensive 12-hour operation before they found source of the pollution.
Following the foul chemical stench, 24 pupils from the school suffered dizziness, nausea and vomiting.
Two teachers and two of the school's canteen operators also experienced the same symptoms.
The primary school's administration instructed the students, teachers and staff to evacuate the school premises immediately.
In a follow-up operation today, lead by Johor Jaya Fire and Rescue Department Senior Fire Officer Salleh Mohamed determined
a factory within a 5km radius of the school had indiscriminately burnt intermediate bulk containers (IBC) containing solid sludge and liquid waste, and disposed its residue into Sungai Tiram.
He said the department despatched 17 personnel including their Hazmat unit to the primary school.
Also deployed to the school were 11 officers from the DoE, 15 Health Ministry medical officers, police, officers from the municipal council and the village community members.
Upon their arrival, they initiated a preliminary assessment to identify the source of the stench believed to be chemical odour pollution.
Hazmat and DoE officers conducted a gas analysis systems and emission monitoring (gasmet) procedure to measure the gaseous emissions at an illegal palm oil processing facility and a plantation nearby.
However, the periodic air quality readings recorded at both locations were within normal ranges.
The Hazmat officers conducted a final detection operation about noon today.
A long-range Scanning Infrared Gas Imaging System (SIGIS 2) was used to remotely sense the surrounding areas, but failed to detect any pollutions.
Salleh said the health ministry medical officers mapped out the victim's symptoms, in an effort to establish the distance the victims were with the source of the pollution.
The mapping efforts established that the victims would have been within a 5km radius to be affected by the pollutions.
He added based on the ministry's findings, the radius was marked into five sectors of a kilometre each.
"We used multiple air pollution detection equipment but the reading in sector one to four, did not record any abnormalities.
"In sector five, located near a factory, the gasmet temperature gas analyser indicated an increase in methanethiol readings," he said, adding it was then that they determined the pollution source.
Meanwhile state DoE director Dr Mohd Famey Yusoff said appropriate actions will be taken against the factory operator, including a "Stop Work Order" (SWO) if deemed necessary.