The widespread use of polychlorinated biphenyls or PCBs has made it tedious to enumerate all the possible source of toxic Monsanto PCBs (Monsanto being the only domestic PCB producer in North America). Basically, however, PCB contamination can occur through its production, and as a by-product of its use.

PCBs are synthetic, which means they do not occur in nature. The first PCB-like substance was a by-product of coal tar. By 1881, German scientists were producing 209 different types PCBs. These differentiated by the number and position of chlorine atoms attached to the two benzene rings (the “biphenyl” in polychlorinated biphenyl), which is the basic composition of the compound. Each type or congener has a different toxicity level, and can range from a thin and light-colored liquid to a black, waxy solid. It depends on the intended use. All PCBs are stable, heat resistant, and non-flammable with a high boiling point. This is what made it such a valuable industrial component.

About 1.5 million tons of PCBs have been produced worldwide, and in its production, thousands of pounds of waste has gone into the rivers and landfills of the surrounding area. This is the primary source of toxic Monsanto PCBs in the US. A secondary source is when it leaks or separates from components or products that used PCB as a coolant, insulator, stabilizing agent, or flame retardant. Industrial transformers are good examples of this type of release. The ground under industrial transformers tested for high levels of PCB contamination, presumably when the PCBs leaked when the temperature inside the transformer rose enough.

Old machines, components, newspapers, PVC pipes, and paint that have been sent to landfills are also a major source of PCBs. As they degrade, they release the PCBs into the ground and the air, which eventually makes it way to the water. From there it is just a fish net away from entering the human system.

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