Text 9677, 89 rader
Skriven 2008-01-07 16:52:02 av Robert Bashe (2:2448/44)
   Kommentar till text 9605 av Roy Witt (1:397/22)
Ärende: Formaldehyde (was: Ethanol)
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Roy Witt wrote to Robert Bashe on Sunday January 06 2008 at 16:08:

RB>> Have to jump in here, Roy, since although formaldehyde (a gas) has
RB>> been suspected of many things for many years, and investigated very
RB>> thoroughly, there is still no evidence to show it is carcinogenic.
RB>> Even if it were, you'd have a hard time inhaling it, since it binds
RB>> with water and would never reach your lungs. Aside from that, it is
RB>> highly irritant at extremely low concentrations (1 ppm and even
RB>> lower) and thus any exposure to elevated concentrations is unlikely.

RW> There's a cloth fiber material that is combined with formaldehyde to
RW> make it a hard board-like product. When machining it, one is exposed
RW> to the formaldehyde contained in the chips, which are actually dust.
RW> Breathing it will do what you say can't happen. I've always worn a
RW> mask like a surgeons when maching it for that reason.

Wearing a dust mask in processes that produce dusting is always a good idea,
since respirable dusts aren't good for the lungs and can cause health problems.
But what you're talking about has nothing to do with formaldehyde.

What you refer to above is a material that has been impregnated with a
phenol-formaldehyde or urea-formaldehyde resin. Such resins, when uncured,
contain a certain percentage of free formaldehyde (max. 5% is usual). After
curing, they contain no free formaldehyde and any residual formaldehyde gas
that might be released to the air by warming during the curing peocess is lost
after the product has been aired for a day or so.

The formaldehyde in the resins is chemically transformed during the curing
process and no longer exists. It cannot be liberated by depolymerization of the
cured resin, and in fact the cured resin is a thermoset: it will not melt or
soften when heated.

No formaldehyde could possibly adhere to the dust from machining, since it
simply doesn't exist anymore and even if it did, it would immediately react
with the moisture in the air. So whatever health problems may be associated
with the dust you mention, at least they have no connection with formaldehyde.

But I want to go back and emphasize one thing I wrote above: formaldehyde has
been investigated for carcinogenicity and many other things for at least the
last 40 years, and often by people with _very_ critical opinions (not to say
people with an agenda). Despite that, despite everything negative ever written
and claimed, formaldehyde is still not classed as a "known carcinogen" even
today. Yes, it is a powerful irritant and under certain circumstances a
mutagen. No, the solution in water (formalin) is not something you want to wash
your hands in. But _because_ of the irritancy and the extremely low threshold
(less than 1 ppm), the danger of exposure to higher concentrations is
negligible (you _run_, do not walk from the source, weeping and coughing all
the time) and because of the chemical reactivity, it's impossible to inhale the
gas: it simply never reaches the lungs and is absorbed in the nose or mouth.

RB>> I've worked with formaldehyde and paraformaldehyde a lot over the
RB>> years, and have dealt with people in the factory who worked with it
RB>> every day over decades. There were no health issues except for an
RB>> occasional problem with the irritant effect.

RW> Imagine that irritant in your lungs...

I can't because that's impossible except in the theoretical (and fatal) case
that you were trapped in a sealed chamber with an atmosphere containing a high
level of formaldehyde gas. But I've often been exposed to a very few ppm and
know how impossible it is to even stay in the neighborhood of that.

RW> I found that it was a skin irritant as well and always washed up
RW> immediately after working with it.

Of course the solution in water (formalin) is a skin irritant. It can also
cause sentitization. But an employer who allows people to work with the
solution would be expected to properly instruct personnel and provide safety
equipment (gloves, gas mask - not merely a dust mask).

As far as the machining dust is concerned, I don't know precisely what was
bothering you, and there are many things that can produce allergies. I would
personally expect problems with asthma and bronchitis in people who worked with
a dust such as you describe without wearing a dust mask. But that would be
because of the dust and organic components (cured resin), not because of
formaldehyde.

RW> There used to be a product made for Avon that would fill the pores in
RW> your skin, so you could just use a rinse and the dust would be gone.
RW> Can't find it these days.

Safety gloves would be advisable if you're having a reaction to such things. In
cases of sensitization, a transfer to another department is usually
unavoidable.

Cheers, Bob

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