JOHOR BARU: The State Environment Department (DoE) detected unusually high levels of ammonia gas in Sungai Pandan and the surrounding area of Kampung Melayu Pandan here at 4pm yesterday.
DoE senior deputy director Mohd Rashdan Topa said air quality measurements taken with a multi-gas detector near Sungai Pandan indicated elevated parameter readings that exceeded the safe air concentration level (AEGL-1).
AEGL-1 refers to an airborne concentration level that, when exceeded, can cause discomfort, irritation, or asymptomatic effects in individuals.
Despite the initial detection of high ammonia levels, air quality readings returned to normal by 1am today.
"The specific chemical responsible for the high concentration detected in Sungai Pandan remains unidentified.
"However, our monitoring revealed that ammonia (NH3) levels were elevated, while other parameters remained within normal ranges," he said.
Residents in areas where ammonia gas was detected reported symptoms such as dizziness and nausea.
"We have also been informed that two residents from the village sought outpatient treatment, but no one has been hospitalised due to the air pollution," Rashdan said during a press conference after visiting the site and collecting water samples from Sungai Pandan.
He said that the gas could have been released by nearby premises or factories, or it might have been illegally dumped into the river.
DoE enforcement officers are focusing their inspection efforts on premises that use ammonia in their operations, such as ice and fertiliser factories.
However, thorough inspections will be conducted on approximately 100 factories operating in the area as part of the ongoing investigation to identify the source of the ammonia gas.
State DoE also deployed drones for aerial monitoring along a two-kilometre stretch of Sungai Pandan, while the Chemistry Department was tasked with analysing the soil and water samples.
Results are expected within a week.
Inspections were also carried out in Taman Daya and its surrounding areas to determine whether any chemical waste had been dumped into the river's source or headwaters, leading to the strong chemical odour in Sungai Pandan.
Despite the strong odour and the river turning black behind Tabika Kemas, drone surveillance did not reveal any visible black spots along the river.
Residents in three nearby housing estates – Taman Daya, Mount Austin, and Taman Istimewa – reported being alarmed by the strong chemical-like odour that persisted from midnight until the early hours of the morning yesterday.