Polychlorinated Biphenyls (PCBs)
What are they?
Polychlorinated Biphenyls (PCBs) are human-made chemicals that are highly toxic and persistent in the environment. They were once widely used in electrical, heat transfer and hydraulic equipment, and in some commercial products like paint, plastics, adhesives and surface coatings. In the 1970s and 1980s, their use was severely restricted due to their harmful environmental impacts, and in 1980 Canada banned their import.
Because PCBs are very stable and do not break down easily, they are still present in the environment today. PCBs can still be found in industrial equipment and electrical installations, and may be released (along with other toxic chemicals) through fires. PCBs can enter aquatic ecosystems through leaks and spills, industrial effluent, and leaching from uncontained landfills. PCBs can also become airborne and travel long distances on wind currents before they are deposited back to land and water in rain and snow.
PCBs are organic molecules that contain chlorine atoms. There are 209 numbered congeners or subtypes of PCBs. These can be organized into groups according to the number of chlorine atoms in each molecule (e.g., monochlorobipenyls have one chlorine atom per molecule, trichlorobiphenyls have three chlorine atoms per molecule).