Study reveals hazardous chemicals in 11 Malaysian rivers, posing cancer risk

SHAH ALAM - Perak River, Kuantan River and Terengganu River which are well-known among anglers, are among 11 rivers in the country detected to have the most hazardous chemicals, namely arsenic and benzo(a)pyrene from used motor oil, which could pose a cancer risk when exposed.

According to an analysis of polycyclic aromatic hydrocarbons (PAHs) by a collaboration of Universiti Putra Malaysia (UPM), Universiti Malaya (UM) and Tokyo University, Japan, the highest concentration of benzo(a)pyrene was found in the Klang River.

The study based on molecular fingerprints was able to prove that the main source of polycyclic aromatic hydrocarbons in the Klang River originated from used motor oil, making it the most polluted river with oil residues.

This is because the Klang River is exposed to various sources infiltrating from urban runoff.

Additionally, Malaysia's 'non-point' pollution sources did not receive treatment systems like in developed countries.

Furthermore, Langat River in Selangor; Pinang River in Penang; Kim Kim River and Muar River in Johor; Besut River and Terengganu River in Terengganu; Kuantan River in Pahang; Melaka River in Melaka; Kelantan River in Kelantan and Perak River in Perak were listed as rivers with the respective hazardous chemicals.

The 25-year study revealed that the main causes of river pollution were due to industries around the river areas such as machine repairs that release untreated used motor oil, thus contaminating the environment.

Environmental Pollution Expert, Cluster Task Force on Environment and Sustainability, Malaysian Professor Academy Professor Dr Mohamad Pauzi Zakaria said the remnants treated at the Sewage Treatment Plants that flow into the river could have adverse effects on the entire river ecosystem.

"The spilled motor oil from vehicle workshops is still not managed wisely and efficiently. These oil residues form part of the surface runoff water and flow into the drainage system, eventually entering the river.

"Urban runoff water that is not properly treated can have adverse effects on the river ecosystem.

"There are studies documenting that toxic chemicals in used motor oil can cause hormonal disturbances and hormone-mimicking (acting like natural hormones) effects on humans," he said.

He added that four components, namely benzo(a)pyrene, fluoranthene, benzofluoranthene, and benzo(ghi)perylene, have toxic properties that pose a cancer risk and have implications for human physiology and processes.

"The side effects can result in low immunity, changes to deoxyribonucleic acid (DNA) and genetics, and instability of terrestrial and aquatic life populations.

"If male children are exposed to food (aquatic life) from these rivers, they are feared to have feminine traits, known as the feminisation of boys," he said.

Benzo(a)pyrene accumulates in the tissues of fish, clams and shrimp.

Starting from 1999, the PAHs analysis study used the standard method of the United States Environmental Protection Agency (USEPA) by sampling sediment from the bottom surface of the water.

Pauzi, who was one of the researchers of the study, sampled sediment from rivers and conducted forensic analysis to search for molecular fingerprinting that could be used as the most hazardous indicator to human health.

From sampling to analysis, it took three weeks and was conducted with researchers and students from three different universities.

In addition, Pauzi said that using motor oil containing benzo(a)pyrene also causes accumulation in the living tissues of aquatic life such as fish, clams and shrimp, which ultimately poses a danger to consumers.

"The reason is that these substances can mimic human estrogenic hormones. These chemicals can pose health risks, including cancer, to humans if they consume seafood from these rivers.

"In addition to benzo(a)pyrene, other substances such as microplastics also have the same effects on humans and aquatic life. Microplastic pollution in rivers and coastal seas in Malaysia has reached a critical level and this is very worrying," he said.

Commenting on the best solution to resolve chemical pollution in rivers, which is mainly contributed by industrial factories, vehicle workshops, and agriculture, Pauzi suggested recycling used motor oil with more innovative management so that the substance did not spill into the rivers.

"Usually, used lubricating oil is recycled, stored improperly in workshops, and, on average, spills into the river during repairs or vehicle and engine servicing.

"In addition, every entity that spills oil needs to be heavily fined to provide a lesson. Formal and informal education to the younger generation at the school level about the dangers of used motor oil if disposed of into the environment is also very important."