Text 9753, 155 rader
Skriven 2008-01-10 16:49:03 av Roy Witt (1:397/22)
   Kommentar till text 9677 av Robert Bashe (2:2448/44)
Ärende: Formaldehyde (was: Ethanol)
===================================
07 Jan 08 16:52, Robert Bashe wrote to Roy Witt:

 RB> 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
 RB>>> 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.

 RB> Wearing a dust mask in processes that produce dusting is always a
 RB> good idea, since respirable dusts aren't good for the lungs and can
 RB> cause health problems.

Right. Which is why we were instructed to use masks, as I said above.
Phenolic board isn't the only materials we were required to wear them
either.

 RB> But what you're talking about has nothing to do with formaldehyde.

I disagree...Phenolic board is considered to be hazerdous material because
of the formaldehyde used to make a phenolic resin mixed with cloth.

Toxicology

      Harmful if swallowed or inhaled. May be harmful in contact with the
skin. Toxicity may depend upon extent of polymerisation and the degree to
which unreacted monomer is present, since both monomers are toxic.

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

I know you're the chemist and I'm merely a layman, but I trust what I've
been taught about the handling and machining of such materials through
people who have your same experience in chemistry. If they say to cover up
and wear a mask, I did, when I was exposed to it.

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

It won't even burn with an acetelene torch applied. It'll char, but never
flame.

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

That red dust does have a weird smell to it, but I can't say what it is.

 RB> But I want to go back and emphasize one thing I wrote above:
 RB> formaldehyde has been investigated for carcinogenicity and many other
 RB> things for at least the last 40 years, and often by people with
 RB> _very_ critical opinions (not to say people with an agenda). Despite
 RB> that, despite everything negative ever written and claimed,
 RB> formaldehyde is still not classed as a "known carcinogen" even today.

I don't think I was afraid of that, but I am sensitive to breathing in
anything but nature's air. My dad died of emphesyma brought on from doing
lot's of things without a mask like; smoking, painting cars, breathing
exhaust fumes in a garage and installing asbestos around furnace pipes. He
always said that you think you're invulnerable to these things when you're
young, but they catch up to you when you get older. Although he lived to
be 83, the last 5 or 6 years of his life wasn't worth living.

 RB> Yes, it is a powerful irritant and under certain circumstances a
 RB> mutagen. No, the solution in water (formalin) is not something you
 RB> want to wash your hands in. But _because_ of the irritancy and the
 RB> extremely low threshold (less than 1 ppm), the danger of exposure to
 RB> higher concentrations is negligible (you _run_, do not walk from the
 RB> source, weeping and coughing all the time) and because of the
 RB> chemical reactivity, it's impossible to inhale the gas: it simply
 RB> never reaches the lungs and is absorbed in the nose or mouth.

Yuk...

 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.

There's another material I refused to work with after a while. It's called
G10, but it has the same structure as phenolic board, except that it's
made of fiberglass sheets, rather than plain cloth. Machining that
produced the same type of dust and once breathed, it remains in your
lungs.

 RW>> Imagine that irritant in your lungs...

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

I was talking about the dust, not the gas.

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

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

If you're working with it after it's cured, then as you say, there is no
gas. Let's speak of the dust produced while being machined.

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

Yeup.

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

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

A machinist can't work a milling machine or a lathe with gloves on, that's
a safety issue. Thus, the use of pore clogging products. I learned that
from a friend who worked at a plant (Rohr-Chula Vista) where they made
trolly cars for the rapid transit systems here. He was the 'fiberglass'
insulation installer and always had an itch.

                R\%/itt



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