On Mon, 03 Jan 2005 20:02:00 GMT, (Harry
Chickpea) wrote:

"Doug Kanter" wrote:

Question 3: The oil in older, larger transformers was there for either
cooling or insulation - I don't recall, and it doesn't matter, since it's
just a point of interest. But, the PCBs were there as a byproduct, not
because they had a purpose.

Nope. The chemicals were there to facilitate heat transfer,
especially in larger grid transformers. Needless to say,
non-conductive liquids with a high boiling point are required for the
task.

http://www.ehso.com/EHSO_PCB.htm

Characteristics and Uses of PCBs

PCBs belong to a family of organic compounds known as chlorinated
hydrocarbons. Key characteristics include: high boiling point, high
degree of chemical stability, low flammability, and low electric
conductivity. Between 1926-29 and 1977, PCB-containing products were
manufactured for use in applications where stable, fire-resistant,
heat-transfer properties were demanded. The most extensive use of PCBs
occurred in dielectric fluids. Such fluids typically have the
following characteristics: a heavy oil appearance, high boiling point,
high chemical stability, high flash point, low electrical
conductivity, and low water solubility. PCBs were also used as
plasticizers and additives in lubricating and cutting fluids. Most
PCBs were sold for use as dielectric fluids (insulating liquids) in
electric transformers and capacitors. Other uses included heat
transfer fluid, hydraulic fluid, dye carriers in carbonless copy
paper, plasticizers in paints, adhesives, and caulking compounds, and
filters in investment casting wax. Although PCBs are no longer
commercially made in the United States, many electric transformers and
capacitors once filled with PCBs are still in service. Additionally,
PCBs currently are being inadvertently produced as byproducts during
the manufacture of certain organic chemicals. PCB Manufacturers and
Trade Names lists some of the manufacturers, who made PCBs and the
trade names of their products.

Why Are PCBs Harmful to Human Health and the Environment
When released into the environment, PCBs do not easily break apart and
form new chemical arrangements (i.e., they are not readily
biodegradable). Instead they persist for many years, bioaccumulate,
and bioconcentrate in organisms. Well documented tests on laboratory
animals show that various levels of PCBs cause reproductive effects,
gastric disorders, skin lesions, and cancerous tumors. Exposure to
PCBs in humans can cause chloracne (a painful, disfiguring skin
ailment), liver damage, nausea, dizziness, eye irritation, and
bronchitis.

While this is basically correct, I suspect it is somewhat out of date.
IIRC, electrical equipment containing PCBs had to be replaced by a
certain date, so there should be no transformers or other equipment
still in service in the US containing PCBs.

I believe that the phase-out was done according to type of equipment
because all the substitutes for PCBs are considerably inferior. (Or at
least that was the case in the lat 70s and early 80s.) The last to go,
I believe, were transformers and such in the basements of large
buildings where the potential damage from a fire was very high.

(Of course that had its own dangers. There was a well publicized case
in the 80s of a transformer fire in the basement of a large building
in New York. The fire did a lot of damage, but the PCB contamination
caused a lot more damage.)

Also, more recent studies have called into question the cancer-causing
effects of PCBs. I believe the general scientific opinion today is
that the link between cancer and PCB exposure is now considered
unproven. (Not that you'd know that from the environmentalists web
sites.) However the rest of the health effects mentioned are
definitely real.
"Sometimes history doesn't repeat itself. It just yells
'can't you remember anything I've told you?' and lets
fly with a club.
-- John W. Cambell Jr.