The New Straits Times, January 29, 1998
Q: THE recent fire at the Hulu Langat rubbish dump was said to have been caused by methane gas explosion. Can you explain the danger of methane or other dangerous substances arising from such landfill areas?
A: BEFORE going into the subject matter, the fire at the Hulu Langat rubbish dump reflects the sad state of affairs of our waste management system.
Since the disposal method for municipal solid waste in Malaysia is largely through landfilling, the fire shows that the method being employed at Hulu Langat could have been mismanaged.
A proper system of landfilling includes, among others, covering the waste with adequate soil to prevent scavenging activities and minimise effects to the environment, proper release of decomposition products such as methane from the anaerobic process, and monitoring of the leachate to ensure that no contamination goes into groundwater and, subsequently, drinking water.
In the case of the Hulu Langat rubbish dump, proper release of methane has not been carried out adequately, thus leading to the fire. An earlier report revealed that brown leachate from the rubbish dump was going into Sungai Micu, one of the tributaries of the Hulu Langat river.
As has been highlighted in the media, methane is one of the gases produced from incomplete breakdown of organic materials under anaerobic or no-oxygen conditions. In such situations, carbon dioxide and water would be the final products released into the environment.
Being the simpest compound, methane exists exclusively as a gas at standard temperature and pressure. In terms of toxicity, methane is a simple asphyxiant; at high concentrations in the air it replaces the air in the lung, causing hypoxia or lack of oxygen.
Once in the lung, the gas easily crosses the alveolar-capillary membrane to be absorbed into the bloodstream, causing depression of the brain and the nervous system. The victim of methane intoxication goes into unconsciousness.
Besides methane, fires resulting from landfill areas have been found to release polychorinated biphenyls (PCBs) into the environment. PCBs, which are known to be chemically and thermally stable, have been found to cause problems because they have a long half-life and are readily taken up by living organisms, accumulating in higher levels of the food chain.
These compounds are readily absorbed when inhaled, ingested or absorbed through the skin. Once in the body, they remain deposited in fat tissues and can cross the placenta to the foetus in pregnant women. A single massive absorption of PCBs can cause a unique skin disease known as chloracne, damage to the liver, blindness, swelling, nausea, vomiting and abdominal pain.
Prolonged exposure to smaller doses of PCBs may cause cancer as PCBs are highly suspected carcinogens. Although additional study is needed to link PCBs with cancer in humans, animal studies have found these compounds to be carcinogenic, teratogenic, mutagenic (causing cancer, foetal death or mutation) and to have developmental effects on laboratory animals.
Besides the gases being released into the atmosphere, leachate from the landfills is also harmful to health as it may contain dangerous compounds originating from the rubbish. This liquid would normally be produced when rain or any water that falls on a landfill sinks into the waste, picking up chemicals as it seeps downward. The leachate, if not well contained, would then contaminate groundwater and eventually gets into our drinking water.
Among the most likely sources of toxic materials in landfills are household products like paint solvents, oils, cleaning compounds, degreasing compounds, and pesticides. In fact, studies have shown that some of the compounds being thrown into landfills may be even more toxic than the products from which they originated.
Although landfill liners are used to prevent the release of leachate from landfill areas, they are not full-proof. In some studies, it has been found that these liners will eventually leak and, in actual situations, may only slow down the release of contaminants into groundwater.
On a final note, the incident at Hulu Langat indicates that we should be putting a lot more attention to our waste management system. Looking at the strategies being employed globally, there is a need for us to adopt and incorporate other methods of municipal solid waste management.
An area that should urgently be looked into is the amount of waste generated - how we can reduce it through education as well as other innovative approaches such as home composting. - National Poison Centre
