Bau Lake remains arsenic


The view of the main Bau Lake and a signboard warning the public of the arsenic level in the water.

A SIGNBOARD warning the public against swimming, fishing and bathing in or drinking from Bau Lake because of the high arsenic content – still stands at lakeside.

It was put up by the Natural Resources and Environmental Board of Sarawak (NREB) several years ago. Apparently, some do not heed the warning.

A man was seen fishing from a concrete platform by the lake one morning, using a thin bamboo stem and a hook, specially designed to catch small fish, secured to a nylon line, and earthworms as bait.

When approached, he said he was fishing to pass time.

“Collecting small fish can be very interesting. There are different species in the lake – and some of them are very beautiful,” he added.

At that time, he had already hooked about 30 different types of small fish – still alive.  And he kept them in two bottles – an edible oil plastic bottle for the bigger fish like  tilapia and a smaller mineral water plastic bottle for the smaller fish that looked somewhat like goldfish.

The man did not say what he was going to do with his catch except he may sell some of the good ones to aquarium owners.

Asked if he fried and ate the fish, he replied tidak lah (no).

In fact, the fish in Bau Lake are not recommended for consumption because the water contains a high level of arsenic. If present in high dosage, arsenic has adverse effects on human health.

Going by the warning sign, Bau Lake – popularly known among locals as Tasik Biru – is also not safe for any kind of human activities.

Yellow-colour fish caught from the Lake.

According to NREB’s Annual Environmental Quality Report (2011), the level of arsenic in the Lake is 0.68mg/l – 13.6 times higher than the limit of Class IIB for arsenic in safe drinking water.

Arsenic is metallic mineral with a formula As, light to dark grey in colour. It’s toxic and of not much use except as a poison.

A geologist, who requested anonymity, said arsenic is found in the Lake because of its presence as a component of the mineral – Arsenopyrite (Fe AsS) – and as native arsenic (As), associated with gold mineralisation in Bau area, particularly the Lake.

“When gold was mined, these minerals were exposed. The arsenic was leached into the water body and contaminated it,” he said.

Arsenic can be treated to lower its level in the Lake by various methods, including neutralisation with lime and other chemical agents.

However, the geologist noted such treatment was expensive and had to be carried out over an extended period of time.

“This is because the source of the arsenic cannot be eliminated as long as it occurs naturally in the mineral deposit.

“The whole deposit has to be mined out and the influx of leaching water prevented to totally eliminate the arsenic contamination. As long as this is not done, the contamination will remain.”

He said as Bau Lake had never been “treated,” its water is not safe for human activities such as swimming or bathing, let alone drinking.

He said the safe arsenic level recommended for human activities is up to Class III of the National Water Quality Standard of Malaysia (NWQSM) – that is from 0.05mg/l to a maximum of 0.4mg/l.

“Above this level, activities can be carried out with minimal water contact with the skin.”

A section of the canteen and car park at Bau Lake.

On the arsenic level in Bau Lake, NREB controller Peter Sawal said regular tests carried out by the board between 2011 and now showed almost similar results.

Except for the Bau Jong Regatta, there are no other human activities in the Lake – unlike the old days when swimming and bathing were quite common.

Peter said the Jong Regatta could be held as long as there was minimal contact with the water.

He advised participants to take safety measures, saying: “Make sure no one falls in and accidentally swallows the water.”

However, he pointed out that if people jumped into the Lake just once, their health would not be affected but if it would be different if they swam, bath in or drank from the Lake long term.

The Jong Regatta is a mini-sailboat race – a traditional water sport, organised since 1950 during the colonial era, and is still being held annually.

Arsenic occurs in inorganic and organic forms. Inorganic arsenic compounds (such as those found in water) are highly toxic while organic arsenic compounds (such as those found in seafood) are less harmful to health, according to the World Health Organisation (WHO).

WHO said people were exposed to elevated levels of inorganic arsenic through drinking contaminated water, using contaminated water in food preparations, irrigation of food crops, industrial processes, eating contaminated food and smoking tobacco.

Long-term exposure to inorganic arsenic – mainly through drinking contaminated water, eating food prepared with this water and eating food irrigated with arsenic-rich water – could lead to chronic arsenic poisoning.  Skin lesions and skin cancer were the most characteristic effects, it added.

In addition to skin cancer, WHO noted that long-term exposure to arsenic may also cause cancers of the bladder and lungs.

It said other adverse health effects that might be associated with long-term ingestion of inorganic arsenic included developmental effects, neurotoxicity, diabetes and cardiovascular disease.

According to WHO, fish, shellfish, meat, poultry, dairy products and cereals can also be dietary sources of arsenic, although exposure from these foods is generally much lower compared to exposure through contaminated groundwater.

In seafood, arsenic was mainly found in its less toxic organic form, it said.

The International Agency for Research on Cancer (IARC) has classified arsenic and arsenic compounds as carcinogenic to humans, and also said arsenic in drinking-water was carcinogenic to humans.

There are fears the arsenic content in the Lake might pollute the drinking water in Bau and Kuching but Peter said consumers need not fear as the arsenic in the Lake did not affect the quality of water at the intake point in Seniawan and Batu Kitang.

He explained water from the Lake flowed into Sungai Sarawak Kanan below the intake point in Batu Kitang or Seniawan.

He said even if the Lake overflowed during flooding, the arsenic level at the water intake point in Siniawan and Batu Kitang would be lower than in the Lake due to the dilution factor and the volume in the river.

The serene surroundings and the greenish blue water made Bau Lake a popular picnic spot in bygone days.

The safe level in drinking water is 0.01mg/l by WHO standard and 0.05 mg/l or equivalent to Class IIB of NWQSM.

NREB carries out water quality monitoring in Bau Lake twice a year. The water sample is analysed to determine the arsenic level.

Peter said NREB had conducted a study on people said to have been exposed to arsenic in the Lake between 2004 and 2005. Nail and hair samples were collected from the participants.

“The study, however, did not detect any symptoms caused by exposure to arsenic. There was no indication arsenic had caused any adverse health effects to any of the participants involved in the study.”

Bau Lake was formed from an open cast gold mining pit known as Tai Parit mine, operated by the Borneo Company from 1898 until it was flooded in 1921. It was then known as Tai Parit Lake and subsequently became a popular picnic spot.

Some basic facilities were built around the lake way back in 1975, including a bridge across a narrow part of the lake for to get to the other side of the lake, several shades for visitors to rest and enjoy the beautiful scenery.

Two or three diving springboards were also provided.

After the upgrading, the Lake was renamed Tasik Biru as the water appears greenish blue – due the reflection of the surrounding green plants and the blue sky.

In the old days, Tasik Biru was a centre of attraction in Bau, located less than a kilometre from the town bazaar.

At one time, it was a popular place for swimming and bathing among visitors and picnickers, especially during weekends.

Tasik Biru was closed in June 1990 for dewatering works, carried out by a mining company extracting gold ore from the side and bottom of the lake.

Following the closure, Bau seemed to have lost its glory and reputation as a top tourist destination for locals as well as foreign visitors.

Tasik Biru was reopened to the public in 2009.

The facilities are much better today. There are a few stalls selling food and drinks, toilets, pontoon gangway, viewing platform, footpaths, railings by lakeside, a car park and landscaping.

The new lake resort or area is much bigger than previously. But Tasik Biru now is a farcry from its former appearance.

In the past, the Lake had more natural setting while now, the surroundings are rather bare as a result of mining activities.