Along with DDT, the initials PCB have come to symbolize the hazards of chemical pollution in the environment. PCBs, or polychlorinated biphenyls, are a class of synthetic compounds that were first commercially produced in 1929. The chemical was marketed in the United States until the mid 1970s when the sole domestic commercial manufacturer voluntarily discontinued production. Although the chemical has many uses, the most widespread application was as a fire-resistant dielectric fluid for electrical equipment such as transformers, capacitors, switches, circuit breakers and related gear.
More than one billion pounds of PCBs were produced and used between 1929 and 1979, when the federal EPA banned their production and strictly regulated their usage. However, that did not end the problem of what to do with the hundreds of thousands of transformers already in use.
Because of the pervasiveness of transformers, the PCB issue has become a significant financial risk factor for many industrial plants, government facilities, electric utilities, and other facilities such as hospitals, educational institutions, large office buildings, retail complexes, and others. Among industrial facilities, PCBs are especially likely to be found in the plants of power-intensive industries such as pulp and paper mills, metal smelters and fabricators, chemical plants, oil refineries and similar operations.
Passage of the Toxic Substances Control Act (TSCA) in 1976 declared PCBs to be an "extremely toxic and carcinogenic" substance. Although PCB exposure may cause a severe form of acne, the National Cancer Institute has said there is no evidence that PCBs induce cancer in humans. In TSCA, Congress directed the EPA to ban all future manufacture of PCBs and to regulate most materials containing PCBs.
It is the fire retardant nature of PCBs that made them particularly well suited for use by the electrical industry. Askarel type fluids (manufactured under a variety of trade names and generically called askarel) are comprised of 40-80 percent PCB (400,000 to 800,000 ppm) and 20-60 percent Trichlorobenzene and were produced specifically as "pure" PCB fluids. Askarels are dielectric fluids containing many different PCB cogeners. They are very stable and exhibit low flammability, high heat capacity and low electrical conductivity. Askarel-filled transformers were used in areas where fire safety was a concern, such as inside or near buildings.
The problem with askarels is that when burned they can be converted into far more toxic substances such as dioxins and furans. A series of major building fires in the United States gave national media attention to the problem and resulted in extensive cleanup costs and litigation related to PCB exposure. Subsequently, more stringent EPA regulation occurred. The pressure and expense of meeting EPA deadlines, combined with the threat of millions of dollars for cleanup costs and litigation, has presented all transformer owners with a critical risk management task.
Mineral oil-filled transformers also present potential risk, and are subject to stringent regulation, depending upon the level of PCBs present. During the 50-year period of unregulated PCB use, large numbers of mineral oil units were inadvertently contaminated with PCBs... usually as a result of using common servicing equipment between askarel and mineral oil transformers. Most of these units have under 3000 ppm of PCBs, although much higher concentrations have been found. Unlike askarel-filled transformers, mineral oil-filled units are typically located outdoors in substations and are usually the larger, higher voltage units.
Under EPA definitions, any transformer containing more than 500 ppm/PCB is classified as a "PCB transformer." Those containing 50-500 ppm are classified as "PCB-contaminated transformers," and those containing less than 50 ppm are classified as "Non-PCB transformers."
There is much confusion among transformer owners regarding PCB terminology as, historically, it has been the askarel-filled transformers (600,000 to 800,000 ppm) that have been called "PCB transformers." Additionally, technologies for reducing PCB levels in transformers typically revolve around the type of fluid (askarel vs. mineral oil) and not the 50 or 500 ppm cutoff points.
Transformer owners must recognize that an EPA-defined "PCB transformer" may be an askarel unit or a mineral oil-filled unit with over 500 ppm/PCB.
Options for "solving" askarel-type transformer problems include total disposal and replacement or retrofill/reclassification to "Non-PCB" status (less than 50 ppm/PCB). For mineral oil units, the options include total disposal and replacement, retrofill/reclassification with drained oil being incinerated or chemically treated, or chemical treatment directly on the transformer.
In its PCB rules issued in 1982, the EPA prohibited after October 1, 1985 the use of PCB transformers and PCB-filled electrical equipment (with PCB concentrations of 500 ppm or greater) that pose an exposure risk to food or feed and required weekly inspections of such equipment for leaks. Under the July, 1985 PCB rules, many commercial buildings have an October 1, 1990 deadline to reclassify or dispose of PCB transformers (greater than 500 ppm/PCB whether askarel or mineral oil).
