Just found this - very interesting. Pro's and Con's of polythene - including the carcenagenic materials that would be released should a fire occur!!!
Harmful effects of polythene bags
by S. Vasantharuba , PGIA University of Peradeniya
Polythene is a product of the plastic family. Linking together of many ethylene molecules gives polyethylene or polythene. This process is called polymerization-linking together of monomers to give a polymer.
Usually polythene is manufactured by gas phase polymerization. The manufacturing process of polythene does not yield complete polymerization but create different kinds of monomeric vinyl chlorides. Heavy concentration of these substances is highly toxic and may even cause cancer. Polythene is made with presence of benzyl peroxide an organic solution, for example benzene liquid, butane or propane. Polymers provide polythene with improvements in ridigity and flexibility, toughness, scuff and heat resistance and clarity.
The molecules of polymers are so small that bacteria or fungus cannot get through. Moreover they are very tightly bound. Polythene is a very durable thermoplastic product. It does not get decomposed in any natural process even in hundred years. It is not therefore biodegradable and thus not environment friendly. By changing the production process we can get different plastic commodities. Normally low-density polyethylene (LDPE) is used in packaging, lamination and bags preparation. It is more flexible than high-density polyethylene. (HDPE).
The polythene bags were first introduced in our country in the early eighties. The people, who were using paper bags and cloth bags, switched over to the disposable polythene bags step by step. Earlier people had to buy the bags and they had a habit of reusing. But recently the bags are so readily available, cheap and thin that shopkeepers provide polybags with almost all items. Therefore people started to discard the bags just after one use. According to the statistics from Bangladesh, more than 6.5 million polybags are used daily and nearly 5.2 million used polybags are discarded in their capital city Dhaka.
Polythene is said to be one of the major inventions of mankind, which have greatly helped in packing foods and carry things especially kitchen and domestic goods. Polythene bags have many advantages over the traditional cloth and paper bags. Polybags does not tear like paper bags. It does not become filthy like the cloth bags. And even if it does get wet accidentally, it protects the contents within it, like a mother hen protecting its roost from rain. It is strong, sturdy, and reliable. And it comes in different ranges of colours, sizes and quality.
People use polythene their daily life but they are not aware of the procedure of managing it properly. The people habitually throw polythene bags indiscriminately and carelessly in the streets, open spaces and the drains. This will put burdens on the nature's assimilating capacity. In the long term polybags can cause serious environmental hazards and harmful effects on human health. These harmful effects are commonly called as polythene menace. The following reasons will ensure the reduction of polythene bag usage.
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Plastic bags are non-biodegradable. When they are thrown away, they cause potentially eternal havoc - clogging drains, crating backflow in sewage pipes, causing bad smells, water logging and floods.
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Polythene bags are responsible for spreading various diseases through pond like accumulation of sewage. There are more than 80 diseases caused by water borne germs. These germs generate from contaminated and stagnant sources of water. Contamination of water occurs due to irresponsible disposal of polythene bags into the drains and sewage lines. Polythene bags are also used as breeding places for mosquitoes by storing stagnant water.
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The effect of the polybags is deadly in the waters too. Being light they are carried afar and even into the sea, causing immeasurable harm to marine life. Streams and rivers are affected too.
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Polythene will block the rainwater seeping into the soil and greatly reduce recharging of ground water.
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Burying the polythene bags in the mountainous regions continuously may reduces the vegetation and hence soil binding. This will increases the risk of landslides. They also destroy the local eco-system, and retard the soil's carrying capacity.
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The dumping of polythene on ground has no chance to degrade into soil, which becomes unsuitable for any type of construction.
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When dumped in soil polythene does not allow emission of the toxic gases and pollutants from the earth. Sunlight, its ultra violet ray in particular, which acts, as 'vitamin' for natural fertilization of soil cannot pass through the polythene into the soil, subsequently the capacity of soil to yield agricultural produces is diminished. Due to their non-porous nature they seal off air, thus affecting plant life. International Rice Research Institute found that polythene destroys the bacteria of soil causing loss of soil fertility.
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Polybags have harmful effects on animals. Our Dehiwala national zoo has lost many animals to the polythene menace, a gorilla in the eighties, thirty-six deer since 1997, two wallabies, three ostriches, one giraffe and recently an albino deer. Many street roaming cattle and goats and some wild deer also lost their life due to this polythene menace. These animals had eaten polythene with foods little by little over a long period of time. The contents had solidified inside their abdominal cavity pressing against their intestines resulting in their death.
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The use of polythene bags for preserving foods in the refrigerator is dangerous. Some polythene may contain carcinogenic chemical Dethal Hexane due to incomplete polymerization. This chemical may leaches to foods when foods are refrigerated for a long time. Some plastic bags contain toxic dyes that can pass into foodstuffs endangering consumer health. Most of the brightly colored polythene is contain lead and cadmium.
These toxic substances may destroy the human immune system and causes skin diseases.
- Burning polythene bags is dangerous as they release Dioxin and Hydrogen cyanide, the most carcinogenic and toxic substances. Inhalation of the poisonous gas causes severe and chronic health problem. These gases will pollute the air also.
The above-mentioned harmful effects can be minimized by adopting some alternative options. Those are as followed.
- Awareness should be grown through demonstration of the impact of polythene on human health and environment. This will lead the people to be ecology conscious. Government can undertake campaign programme. Government can publicize its anti-plastic campaign through hoardings, posters, banners, newspapers and electronic media.
So that people in general become conscious about their behaviour while they dispose of solid waste including polythene bags. The 3R principle (reduce, reuse and recycle) can adopted for the control and management of polythene bags.
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Another option is to provide with suitable and affordable alternative. Common alternatives is to choose cloth or paper bag.
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Recycling of polythene bags can be encouraged but should be in a controlled and hygienic way without causing any adverse impact on health and environment. But plastics cannot be continuously recycled. Since most polybags are already made of recycled materials, further recycling them is difficult.
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Burning of polythene bags should be done in a closed chamber reducing the chances of releasing poisonous gases into atmosphere and other processes should be done in an environmentally should manner.
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One alternative can be biodegradable plastic and polythene, which are widely used in the developed countries. One such alternative is biodegradable plastic eco foam. Eco foam is similar to polystyrene, which readily bio degrades, dissolves in water and is made from corn. Another biodegradable plastic and polythene is biopol made from renewable materials such as cotton and cornstarch.
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The newly innovated food grade polythene technology can be shared from developed countries. The technology and incentives can be provided to the polythene manufacturers for producing health and environment friendly product.
Government can resort to economic policy instrument like tax, fine, penalty to address the use of polythene bags and proper disposal of solid waste including polythene bags. These can be implemented in holy places (eg: Sripada, Kataragama), tourist spots ( world's end) and national zoo. Government can set up many collection points for the disposal of plastic wastes in major cities.
Then these wastes can be recycled or burned in a closed
chamber.