The vast majority of plastics are composed of polymers of carbon and hydrogen alone or with oxygen, nitrogen, chlorine or sulfur in the backbone. The backbone is that part of the chain on the main “path” linking a large number of repeat units together. To vary the properties of plastics, both the repeat unit with different molecular groups “hanging” or “pendant” from the backbone.
Some plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point and one or more glass transitions. Semi-crystalline plastics include polyethylene, polypropylene, poly (vinyl chloride), polyamides (nylons), polyesters and some polyurethanes. Many plastics are completely amorphous, such as polystyrene and its copolymers, poly (methyl methacrylate), and all thermosets.
BPA (bisphenol A) is the chemical found in plastic food containers, eyeglass lenses and CDs, and researchers fear it may cause heart disease and diabetes. Some of the constituents of plastic such as
benzene and vinyl chloride are known to cause cancer.The chemical Bisphenol A, used to harden plastics in baby bottles, food containers, cling wrap, toys, CDs, sunglasses, and thousands of other products, may be harmful. Tests on animals and other research indicate that it can be toxic even at very low doses.
Past studies found that this chemical, also known as BPA, may cause a wide range of health problems, including breast and prostate cancer, infertility, diabetes, brain damage, even obesity. It is part of a class of chemicals that scientists say disrupt the hormonal system, mimicking the effects of hormones such as oestrogen and testosterone.
The discovery of plastics revolutionized our society by introducing an enormous and expanding range of products and have displaced many traditional materials—such as wood, stone, horn and bone, leather, paper, metal, glass and ceramic—in most of their former uses. We use plastic in an innumerable ways in our daily life such as food storage containers, water and milk bottles, packaging and carry bags, pipes, electronic items, frames, electric wiring, toys, furniture, cloths, injection syringes and other several thousands of items.
But plastic is one of the major toxic pollutants today. Plastic is a non- biodegradable substance, composed of toxic chemicals, plastic pollutes
earth, air and water. Plastic causes serious damage to environment both during its production and disposal. The major chemicals that go into the making of plastic as ethylene oxide, benzene and xylenes are highly toxic and pose serious threat to living beings of all species on earth. These chemicals can cause an array of maladies ranging from birth defects to cancer, damage the nervous system and the immune system and also adversely affect the blood and the kidneys. Also many toxic gases are emitted during recycling of plastic.
More than a 100 million tonnes of plastic is produced world-wide each year. Disposal of plastic through recycling, burning, or landfilling is a myth because it does not undergo bacterial decomposition. Once plastic is produced, the harm is done once and for all. Plastic wastes clog the drains and thus hit especially urban sewage systems. The plastic wastes being dumped into rivers, streams and seas contaminate the water, soil, marine life and also the very air we breathe. Choked drains provide excellent breeding grounds for
disease-causing mosquitoes besides causing flooding during the monsoons
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