Air Quality: PCBs

PCBs

What are PCBs?
PCB stands for Polychlorinated biphenyls. PCBs are categorized as long-lasting, non-corrosive and relatively non-flammable chemicals. They were first manufactured for commercial use back in 1929. For over four decades PCBs were widely used in a variety of industrial products including cutting oils, sealants, caulking compounds, inks, carbonless paper and paint additives. One of the most common uses for PCBs was in coolants and lubricants in closed electrical applications, such as transformers and capacitors.

In the early 1970s, issues were raised regarding the impact of PCBs on the environment. By 1977, PCB use was banned in North America. The chemical could no longer be manufactured or imported. The use of PCBs in electrical applications has been gradually phased out and there are now strict guidelines for the handling, storage and disposal of the chemical.

Where are PCBs found?
Studies have found that there are trace levels of PCBs throughout the environment around the world. It is believed this resulted from the improper disposal of the chemical, accidental releases from the 1930s to the 1970s and the long-range movement of PCBs by global air currents. After PCBs have been released into the environment they remain there for many years and are not easily broken down. Another concern with PCBs is that they are inclined to bioconcentrate as they advance up the food chain, and tend to collect in the fatty tissues of both animals and human beings, where they can remain.

Exposure to PCBs
Exposure to small quantities of PCBs occurs through food and to a smaller degree through air and water. Consequently, there will be a trace amount of PCBs in both body fat and blood. However, it is not likely that these amounts will cause any negative health effects. It has been estimated, based on results from Canadian Market Basket Surveys and other sources, that the intake of PCBs from all sources on a day-to-day basis is equal to less than one microgram per day for the average Canadian. Exposure to PCBs can increase through the consumption of certain tainted foods such as sports fish, wildlife or marine animals.

Another source of exposure can result from inadvertent releases, such as fires involving PCBs. The fire results in the release of PCBs into the environment and can create an additional threat of exposure. As well, when PCBs are burned, there is a chance that they will be converted into a variety of harmful chemicals. After a fire, airborne particulates holding these harmful chemicals may end up on a variety of surfaces, including water and soil, creating the possibility for people to be exposed.

PCBs Impact on Health
Most of what is known about the impact of PCBs on health is tied into higher levels of exposure (i.e. - occupational or accidental). Some of the more negative impacts on health include a severe type of acne, swelling of the upper eyelids, numbness of limbs and weakness and muscle spasms. However, these health effects mentioned occur at far higher levels of exposure than those that are typically encountered in the environment. Currently, members of the scientific community agree that short-term, low-level exposure to PCBs is not likely to have a great impact on health.

Health Canada has implemented a series of PCB exposure limits for several foods eaten by Canadians. They along with other federal regulatory agencies also watch "average" Canadian diets, certain foods, air and water to ensure that individuals are not exposed to levels of PCBs that would create a health risk. As well, research is continuing to investigate the impact on health of prolonged low-level exposure to PCBs.