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Old 15th March 2006, 12:10 AM   #1
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Default Polychlorinated Biphenyls?

They're in the news lately.

Personally, I have to believe that the PPM and PPB limits of exposure most people out there worry over have to be off the charts. I have to believer this because I assume that in the course of our tinkering, we may have exposed ourselves to PCBs far in excess of the limits prescribed by those interested gov't agencies.

PCBs were used up till the seventies primarily in transformers, capacitors, and fluorescent light ballasts - as coolant (heat xfer), lubrication, and fire resistance.

Everyone jokes about the times something nearby has "lost it's magic smoke". Most likely, it was from one of those devices described above.

Not to alarm here.. I just thought it bears a little repeating that care should be taken when vintage electronics flame out; or when tinkering generally with this stuff.
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Old 15th March 2006, 12:52 AM   #2
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PCBs were mainly used in very high voltage gear, power station transformers etc, not common in consumer prodcts.
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Old 15th March 2006, 01:28 AM   #3
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PCB's -- the problem is this miniscule littlle contaminant -- also in DDT and a lot of other molecules in which a Cl is attached to a CH or a H2C=C2H
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Old 15th March 2006, 01:43 AM   #4
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The most likely consumer gear to have them will be capacitors. The ones Ive seen most of were motor run caps. Very often they will be marked as having "PCB trade nameol"(ei. Pyranol capacitor, GE), it was a feature and cost more. PCBs were used for a reason, they are tough and dont degrade, this is part of why they are a problem. If your cap smells like a johhny cake or menthol, suspect PCBs.

They are often still around as they havent failed yet...

Old light ballasts are one of the most common causes of PCB leaks (by numbers though not necessarily by volume). Under 50ppm PCB dielectric oil is considered not contaminated for use, rules may differ for disposal. Sometimes transformers had their oil replaced at some point so are no longer straight PCB, but PCB contaminated. Some industrial products have some amount of PCB as a reaction side product during production, such as some dyes. PCBs themselves are often contaminated with dioxins and furans. In addition to being present as a contaminant from production, PCBs can degrade to more toxic furan and dioxin compounds. PCB-> furans occurs readily with heat and air.

PCB trade names.

Quote:
PCB's -- the problem is this miniscule littlle contaminant -- also in DDT and a lot of other molecules in which a Cl is attached to a CH or a H2C=C2H
PCBs are themselves toxic, said contaminants are ~100+ times more toxic.
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Old 15th March 2006, 12:09 PM   #5
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Quote:
Originally posted by Tweeker
PCBs are themselves toxic, said contaminants are ~100+ times more toxic.
Sorry, I stand corrected. I recollect that chloracne and agent orange syndorme were (are) both attributable to the dioxin contaminant. You wouldn't want to drink bichlorinated biphenyls.
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