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Polychlorinated Biphenyls

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Polychlorinated biphenyls (PCBs) are a group of manmade chemicals. They are oily liquids or solids, clear to yellow in color, with no smell or taste. PCBs are very stable mixtures that are resistant to extreme temperature and pressure. PCBs were used widely in electrical equipment like capacitors and transformers.

The commercial production of PCBs started in 1929.

Since the 1970s and 80s use has been banned or severely restricted in many countries  because of the possible risks to human health and the environment.

Polychlorinated Biphenyls (PCBs) compounds were used as additives in paint, carbonless copy paper, and plastics.

They were used as a plasticiser to make plastics more flexible.

Commercial production of PCBs ended in 1977 because of health effects associated with exposure. In 1979, the U.S. Environmental Protection Agency (USEPA) banned the use of PCBs; however, PCBs are still present in many pre-1979 products.

Of the 209 different types of PCBs, 13 exhibit a dioxin-like toxicity. Their persistence in the environment corresponds to the degree of chlorination, and half-lives can vary from 10 days to one-and-a-half years.

From the 1920s until they were banned in 1979, the U.S. produced an estimated 1.5 billion pounds of these industrial chemicals. They were used in a variety of manufacturing processes, particularly for electrical parts, across the country. Wastes containing PCBs were often improperly stored or disposed of or even directly discharged into soils, rivers, wetlands, and the ocean.

Exposure to PCBs is through food

  • Food: PCBs in food are probably the single most significant source of exposure for people.
  • Surface Soils: 
  • Drinking Water and Groundwater: PCBs are not very water-soluble so it is quite rare for them to be found in groundwater.
  • Indoor Air: Older fluorescent lights found in schools, offices, and homes may still contain transformers or ballasts that contain PCBs. 

Case Studies ( almost complete) from the world bank website

PCBs are toxic to fish, killing them at higher doses and causing spawning failures at lower doses. Research also links PCBs to reproductive failure and suppression of the immune system in various wild animals, such as seals and mink.

Large numbers of people have been exposed to PCBs through food contamination. Consumption of PCB-contaminated rice oil in Japan in 1968 and in Taiwan in 1979 caused pigmentation of nails and mucous membranes and swelling of the eyelids, along with fatigue, nausea, and vomiting.

Due to the persistence of PCBs in their mothers’ bodies, children born up to seven years after the Taiwan incident showed developmental delays and behavioral problems. Similarly, children of mothers who ate large amounts of contaminated fish from Lake Michigan showed poorer short-term memory function. PCBs also suppress the human immune system and are listed as probable human carcinogens.”

Dioxins are classed as a persistant organic pollutants, (POPs), also known as PBTs (Persistent, Bioaccumulative and Toxic) or TOMPs (Toxic Organic Micro Pollutants.)

Find out more about dioxins here.

POPs are a small set of toxic chemicals that remain intact in the environment for long periods and accumulate in the fatty tissues of animals. You can find out more about POPS here

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