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PCBs, or Polychlorinated Biphenyls, are man-made chemicals. Their use is strictly controlled or banned in many countries because they pose a threat to both human health and the environment. Polution from various types of PCB materials is a major problem around the world because the chemicals are persistent organic pollutants, meaning that although PCB manufacture is mostly banned across the world, their previous use is still having an environmental impact today.

What Are PCBs?
There are more than 200 different PCB compounds, all of which share several common properties. These include resistance to acids, bases and heat, being highly unreactive and not being very soluble in water, but very soluble in fats. Because of these qualities which aren't necessarily shared by natural chemicals, PCBs have been used in the manufacture of insulation, electrical appliances, inks, adhesives and components and in fire retardant products since 1929.

Why Do PCBs Pose a Threat to Health & The Environment?
PCBs have been banned in many countries worldwide since the 1970s because of the threat to human and animal health and the environment posed by their toxicity. Since 1929, 2 million tons of PCBs have been produced and according to the Green Facts website, around 10 percent of these remain in the environment.

How Do PCBs Enter the Environment?
PCBs enter the environment when appliances and other products of which they are part are disposed of in landfill. This releases PCB pollution into the air. PCBs can also contaminate water bodies and soil, contaminating the food chain, and may also evaporate into the air from large water bodies. North America's Great Lakes are polluted with PCBs according to the Green Facts website.

Where are PCB Traces Found?
Because of their tendency to bioaccumulate, meaning that once they are in the environment or in a living animal or person, it is difficult to get rid of them, PCBs can be found in many biological samples, such as human blood, milk and fatty tissue as well as in the tissue of many animals and fish and in dairy products. They can also be measured in water, the air, soil and sediment.