PCB were discovered in the 19th century. At that time, cars became widely used and the demand for gasoline was increasing. Gasoline is refined from crude oil, and large amounts of chemicals, such as benzene, are released in the process. When benzene is heated, chlorine is added to produce a new chemical called Polychlorinated biphenyls (PCB). So far, there are 209 related substances in PCB, numbered according to the number of chlorine ions they contain and where they are inserted.

Nature and Use

PCB is an industrial chemical with the following properties:

1. Heat transmission is strong, but no electricity transmission.

2. Not easy to burn.

3. Stable property, no chemical change.

4. Does not dissolve in water, is a fat soluble substance.

Because of these properties, PCB were initially considered a godsend by the industry and were widely used as dielectric, in electronic devices such as capacitors and transformers, or as a heat-exchange fluid to regulate the temperature at which instruments operate.

In the early days, people did not know about the toxicity of PCBS and did not take precautions, and dumped a large amount of PCB waste into the ocean. It was not until workers who produced PCB began to fall ill and environmental scientists found PCB content in Marine organisms that people began to pay attention to the problems caused by PCB.

How does PCB enter the body

A lot of PCB waste accumulates in landfills, which can release gas. Over time, the waste can end up in lakes or oceans. Although PCBS are insoluble in water, they are soluble in oils and fats, which can accumulate in Marine organisms, especially larger ones such as sharks and dolphins. PCBS are inhaled when we eat such deep-sea fish or other contaminated food, including dairy products, meat fats and oils. PCB ingested is mainly stored in human adipose tissue, can be transmitted to the fetus via the placenta during pregnancy, and also released in human milk.

Effects of PCB on human body

Damage to the liver and kidneys

Skin causes acne, redness and affect pigment

Eyes are red, swollen, uncomfortable and secretions increase

Nervous system reaction retardation, paralysis of hands and feet tremor, memory decline, intelligence development blocked

Reproductive function interferes with hormone secretion and reduces adult fertility. Babies are more likely to suffer from birth defects and slow growth later in life

Cancer, especially liver cancer. The International Organization for Research on Cancer has classified PCBS as possibly carcinogenic

Control of PCB

In 1976, Congress outlawed the manufacture, sale and distribution of PCBS.

Since the 1980s, several countries, such as the Netherlands, Britain and Germany, have imposed restrictions on PCB.

But even with the restrictions in place, global production was still 22 million pounds a year in 1984-89. It does not seem feasible to stop PCB production worldwide.

conclusion

PCB pollution, accumulated over the years, can be said to be global, almost all food is more or less contaminated, it is difficult to completely avoid. What we can do is pay attention to the food we eat, raise awareness and concern about environmental protection, and hopefully encourage policy makers to take appropriate controls.