Text 9760, 104 rader
Skriven 2008-01-11 20:57:46 av Robert Bashe (2:2448/44)
   Kommentar till text 9753 av Roy Witt (1:397/22)
Ärende: Formaldehyde
====================
Roy Witt wrote to Robert Bashe on Thursday January 10 2008 at 16:49:

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.

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

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

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

Then someone needs to go back to chemistry class. As I already mentioned, the
formaldehyde doesn't exist anymore when the resin is cured, and can't be
released by depolymerization since neither phenol-formaldehyde nor
urea-formaldehyde resins depolymerize, both are thermosets.

RW> Toxicology

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

That is misleading, since such resins polymerize completely when exposed to
acidic catalysts. There is no "unreacted monomer". Whoever wrote that was
either no chemist or was citing a text from something else, for example an
epoxy resin. Or was simply trying to "cover his ass" for all eventualities,
past, present and future.

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

And you're wise to do that. Organic dusts are definitely a health hazard and
it's better to be overcautious than make a mistake and suffer the consequences
years later.

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.

RW> I don't think I was afraid of that, but I am sensitive to breathing in
RW> anything but nature's air. My dad died of emphesyma brought on from
RW> doing lot's of things without a mask like; smoking, painting cars,
RW> breathing exhaust fumes in a garage and installing asbestos around
RW> furnace pipes.

Brother! That's quite a combination. Particularly the asbestos, since blue
asbestos - the really nasty respirable kind - was often earlier used for
insulation. Did he have asbestosis? That would account for the emphesema.

RW> He always said that you think you're invulnerable to these things when
RW> you're young, but they catch up to you when you get older. Although he
RW> lived to be 83, the last 5 or 6 years of his life wasn't worth living.

I can believe it, and he was also right when he said the young think they're
invulnerable. That unfortunately makes them incautious and sometimes the
results are permanent. Unfortunately, you can't go back in time and beat some
sense into your younger self even after you realize you made a mistake.

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

The dust from that would be even worse, if respirable (size and length of the
fibers). In fact, I've read about some work that indicates glass fibers of a
certain length and thickness are carcinogenic when inhaled. People used to
think this depended on the chemical composition of the fibers (as in asbestos),
but although that may also be a factor, it apparently is a question of their
physical characteristics as well.

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.

RW> A machinist can't work a milling machine or a lathe with gloves on...

Not even skin-tight surgeon's gloves? I know it's dangerous to work on machines
with work gloves, since they can get caught in moving parts and cost you a hand
or arm, but tight-fitting gloves must be reasopnably safe.

RW> Thus, the use of pore clogging products. I learned that from a friend
RW> who worked at a plant (Rohr-Chula Vista) where they made trolly cars
RW> for the rapid transit systems here. He was the 'fiberglass' insulation
RW> installer and always had an itch.

I can believe it. That's always a problem with fiberglass, and you really
should only handle it with gloves. But even then you can get tiny fibers in
exposed arms when working... very difficult to avoid.

Cheers, Bob

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