Bill
Unfortunately, technocrats who propose ruling are not scientists. There
is not a single shred of evidence that methylene chloride is
carcinogenic to man. It is not carcinogenic to rats or hamsters, either.
An increase in lung and liver tumours has been observed in both sexes of
the B3C6F1 mouse. This difference is explained by different
metabolisation paths (in mice, through the glutathione-S-transferase
pathway, which is negligible in other species, including homo sapiens).
Observations in vitro on human tissue has also revealed negative
effects.
What we forget is that we have been using this and other chloromethanes,
as well as chloroethenes and, more recently, chloroethanes for over 70
years in industry, often under the most uncontrolled conditions in the
earlier years. Two of the other chloromethanes are known to provide a
good basis of doubt (carbon tet and chloroform) in epidemiological
studies and their metabolic science is reasonably well known. All three
of the non-ozone-depleting common chlorinated solvents (MC or DCM, TCE
and PCE) are in a similar position with little risk of carcinogenicity
under normal working conditions, unless there are confounding factors,
such as tobacco, alcohol or severe air pollution, as well as concomitant
substances such as epoxide stabilisers (common in the past). I
personally recommend that anyone working with chemicals should be very
moderate in their habits, whether the products are halogenated or not.
The European Centre for Ecotoxicology & Toxicology in Brussels has
published two reports on MC and one each on TCE and PCE, all of them
highly scientific, written by international committees of expert
toxicologists and epidemiologists and peer reviewed by 10 - 15 others.
All three chlorocarbons are shown to be non-carcinogenic to humans,
under the closest scrutiny. The summary of the one treating MC and
specifically human carcinogenicity concludes in the following sentences.
"A risk assessment taking into account these differences in metabolic
rates between the species indicates that the computed risk of cancer in
man is negligible under normal use conditions. The current hygiene
standards which are based on the need to restrict the degree of
formation of carboxyhaemoglobin after metabolism of methylene chloride,
adequately protect man from the carcinogenic risk of exposure to
methylene chloride." By "negligible", this is dose-dependent. Based on a
70 kg man working under normal industrial conditions for 8 hours per
day, 5 days per week for 35 years of a 70 year lifetime, the risk of
tumour development for a constant dosage of MC is modelled at:
10 ppm 6.52 x 10^-9
30 ppm 7.99 x 10^-8
50 ppm 2.72 x 10^-7
100 ppm 1.50 x 10^-6
From these figures, it can be seen that roughly 1 person in a billion
thus exposed may develop a cancerous tumour from exposure to MC over 35
years at the current OSHA PEL of 25 ppm. Otherwise, if every single man,
woman and child in the USA worked, as an adult, under such conditions,
exposed to MC, there would be less than one case per century of
ascribable tumours. This is really negligible.
As for decaffeination, I believe that no chlorocarbons have been used
for this in Europe for decades. I remember when it was carbon tet, but I
think this was replaced by 1,1,1-trichloroethane about 45 years ago, in
turn replaced by purely aqueous methods about 25 years ago. You can buy
your decaf Nescafé or Café Haag safely in Europe! (Coffee without a kick
is a non-starter, but that's another story! My favourite non-alcoholic
tipple is what you probably know as Turkish coffee but known here as
Cyprus coffee: 1 heaped teaspoon of the most finely ground coffee beans,
1 demi-tasse water, just brought to the boil three times and poured into
the cup. After two of those, I can piss stronger than American coffee
:-) )
Brian
"Kasprzak, Bill (sys) USX" wrote:
>
> Anybody look on a container of decaf coffee lately? One of the ingredients
> used in the process, is Methlylene Chloride. See web info below
>
> As with all decaffeination processes, the direct method begins with soaking
> green unroasted beans. The beans are then flushed with methylene chloride
> (DCM), a solvent that is generally used in direct contact with the beans. As
> the DCM soaks through all parts of the bean, the caffeine is drawn out. The
> U.S. Food and Drug Administration (FDA) considers the DCM residual levels in
> this decaffeination process low enough to be acceptable. The FDA, however,
> and the National Cancer Institute have both linked DCM to cancer in
> laboratory animals. In 1989 the FDA banned DCM for use in cosmetics and hair
> sprays.
>
> Who says, not easy to get.
>
> No decaf for me.
>
> Bill Kasprzak
> Moog Inc.
>
> > -----Original Message-----
> > From: Larry J. Fisher [SMTP:[log in to unmask]]
> > Sent: Sunday, March 25, 2001 10:09 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Epoxy Ink Stripper...
> >
> > The best stripping solvent I know of for cured epoxy materials is
> > methlylne
> > chloride. The best methlyene chloride "strippers" are the old paint
> > strippers
> > that contain methylene chloride and wax (when the methylene chloride
> > starts
> > to evaporate, the wax forms a barrier at the surface to prevent further
> > evaporation - therefore the methylene chloride can strip further).
> >
> > Methlyene chloride is on the "bad news" list these days and is not easy to
> >
> > get. I'm not sure if you can even get the methylene chloride based paint
> > strippers any more. Furthermore, the methylene chloride can also do a
> > "number" on the butter coat of your laminate. Good Luck!
> >
> > Regards,
> >
> > Larry Fisher
> >
> >
>
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