PCBs

Polychlorinated biphenyls (PCBs) are a group of synthetic chemicals that can have severe health effects on humans. There are many different types of human-made PCB molecules, but they have similar chemical structures, with the formula of C12 H10−x Clx. PCBs were once popular in industry because of their chemical stability, flame resistance, and insulating properties, and were used in a variety of manufactured products. Although there has been much public and legal attention given to their toxic nature, which has resulted in a ban on their production in many countries since the 1970s, PCBs endure in the environment. PCBs are classified as persistent, bioaccumulative, and toxic chemicals. They are considered persistent because they remain in the environment for a long time and break down very slowly. They are soluble in fats, which also makes them bioaccumulative, meaning that these chemicals concentrate, or build up, as they move up the food web.

There are no known natural sources of PCBs, and their appearances range from oily liquids to waxy solids. Before being banned in many countries, these mixtures were commonly used in the electrical industry as cooling fluid or lubricants for transformers and capacitors because they are stable compounds and do not burn easily. In addition, PCBs were used in paints and caulk materials because they increased the durability of paints and provided resistance to water, heat, and chemicals. They have also been used in a wide variety of other materials, including lightbulbs, flame retardants, and carbonless copy paper.

PCBs enter the environment in various ways and have been found in air, water, and soil. When they were used in manufacturing, they entered air, water, and soil during their use and manufacturing processes, as well as their disposal. Also, accidents, fires, and spills have led to PCB contamination. In addition to PCBs that are already present in the global environment, they are still released from improper dumping of industrial wastes and leaking of older electrical transformers that contain PCBs.

Some factories have deposited PCB contaminants into bodies of water over many years. Given that PCB can contaminate the soil, surfacewater like rivers and lakes, groundwater, and even air, the remediation of this pollution is complex. In Pittsfield, Massachusetts, for example, PCB contamination is widespread, and the causes are multiple. For one, when mixtures spilled in the factories of General Electric, workers would commonly put soil on the spill to absorb it. This almost never-ending stream of topsoil was given to the community [Page 308]as a benefit, and it was used in gardens, for building houses and schools, and in parks and playgrounds. In addition, underground lakes were formed by over a million pounds of contaminated oil that was dumped down drains at factories, which resulted in the contamination of a large river and the groundwater. In addition to such localized examples of extreme PCB contamination, there have been multiple international large-scale incidents involving PCBs.

PCBs do not degrade readily, so they persist in the environment. In addition, PCBs bind strongly to soil and can be carried by water or air. In bodies of water, they attach to the sediment, which is the loose material that settles at the bottom, and they can stay there for a long time. They also spread through aquatic habitats as they become absorbed by bottom-dwelling organisms and small fish, and then begin to pass along the food web and accumulate in larger fish and marine mammals. This process is called bioaccumulation, which means that toxins are stored in the tissue of animals. PCBs can also travel through air, and thus the environmental transport of PCBs is nearly global as PCBs move through the atmosphere.

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