PCB were found in the 19th century. Automobile came into widespread use at that time, people's increasing demand for gasoline. Gasoline is distilled from crude oil, in the refining process releases a lot of chemical substances, such as benzene. When heated, benzene, chlorine when coupled, will result in a new chemical called polychlorinated biphenyls (Polychlorinated biphenyls, PCB). So far, PCB there are 209 kinds of related substances according to the chlorine ion number and insert positions but have different numbers.
Properties and uses
PCB is an industrial chemical, properties are as follows:
1. heat transfer ability, but does not conduct electricity.
2. not easy to burn.
3. stable chemical is likely to change.
4. not soluble in water, is a lipid-soluble substances.
Based on the above property, industry first heaven-sent treasure for PCB, is widely used as dielectric, placed in electronic devices such as capacitors and transformers, or as the temperature of the heat exchange fluid to adjust the instrument operation.
Initially, people don't know that PCB toxicity, is not prevented, while large amounts of PCB waste dumping in the sea, until the production of PCB industry workers have been sick, and environmentalists found PCB content in the marine creatures, people start looking at PCB problem.
PCB enters the body
Accumulation of PCB wastes within the land-landfill, will release the gas. Over time, these wastes will flow into lakes or oceans. Although the PCB do not dissolve in water, but insoluble in oil, resulting in the accumulation of marine biology, especially larger organisms, such as sharks and dolphins. This type of deep sea fish that we eat, or eating contaminated food, including dairy products, meat, oil, PCB the air we breathe. PCB intake is mainly stored in human adipose tissue, to her fetus through the placenta during pregnancy, also released in human milk.
PCB effects on the human body
Liver and kidney damage
Cause acne, redness of skin, effect pigments
Eye swelling and discomfort, increased secretions
Nervous system unresponsive, limbs paralysis, tremors, memory loss, intellectual development
Reproductive function interfere with hormones, reduced reproductive capacity in adults, newborn baby in captivity suffer from birth defects, future growth will slow
Cancer, especially liver cancer. International cancer research organization, the PCB has been classified as possibly carcinogenic substances
Control of the PCB
In 1976, the US Congressional legislation banning the production, sale and distribution of PCB.
Since 1980, a number of countries, such as the Netherlands, the United Kingdom and Germany, to impose restrictions on the PCB.
However, even with the restrictions, in the 1984-89 years, global production of 22 million pounds a year. PCB seems to be global to stop production, may not be feasible.
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