[Beowulf] Re: Earthquakes and raised floors...

Gerry Creager N5JXS gerry.creager at tamu.edu
Mon Jan 9 23:14:35 EST 2006


Argh.  I've not dived into my sordid research past in some time.

David Mathog wrote:
> Robert G. Brown wrote:
> 
> 
>>The whiskers are too small to filter without filters that would
>>seriously impede airflow.  Zinc whisker dust in the quantities
>>likely to be breathed in while working on or under raised
>>floors is not thought to be dangerous to humans, as humans
>>actually use tiny amounts of zinc as a nutrient.

Heavy metal dusts are always to be avoided.  There are two issues to 
consider with metal dust inhalation: localized inflammatory response (as 
indicated below) and inflammatory encapsulation.

> We do need a little zinc but the normal way to get it is through
> the digestive system.  Even then it is single zinc atoms that
> are absorbed, not big chunks of metal (biologically a whisker
> is a big chunk of metal).
> 
> I'm a bit dubious about the claim that zinc whiskers aren't
> dangerous when inhaled.   Not because it's zinc so much (although
> other forms are definitely bad if inhaled) but because of
> the long needle shape (like asbestos).  Whiskers seem like exactly
> the sort of material that could get stuck in the lung and cause
> local inflamation and/or cell proliferation. Enough of the former
> effect could eventually lead to emphysema.  The latter effect probably
> has no lower dose limit, since cancers can grow up from a single cell.
> I'd be a lot more convinced if the safety claims actually
> cited experimental data (for instance with rats or mice) where the
> health effects of these whiskers was actually measured.  If there
> has been such a study I was not able to find it with a few keyword
> searches through the journal indices at our library.

Having worked on one of the original clinical trials for zinc 
supplementation to boost immune response in viral respiratory 
infections, I can state with some comfortable authority that oral and 
nasal inhalation of acidified and aqueous zinc in reasonable quantities 
isn't likely to be harmful.  I can also comfortably counsel that I'd be 
leery of inhalation of overt macroscopic metalic dust.  Silicosis-like 
emphysema *is* possible, although it tends to take a larger exposure 
than most would expect, or a hypersensitivity to dust, to kick these 
things off.  The potential for uncontrolled cellular mutation 
originating from a mechanical irritant is not nearly as likely as most 
other potential ailments.

A metallic dust silicosis-like pneumonia or bronchitis can be persistent 
and difficult to cure.  It requires significant physical effort (we tend 
to call it 'pulmonary toilet') and often requires some rather unpleasant 
interventions.  It's not inconceivable that an acute inflammatory 
response could lead to complete consolidation of a lobe or a lung, and 
could require surgical intervention.  Not real likely, but not far-fetched.

By now, I suspect RGB has checked with his local physician to refute 
most of these claims...  We certainly know he won't sit silently!

Off hand, my advice if you're working under-floor is "wear a mask" (do 
as I say...).  Oh, and don't take up cigarettes either.  That's much 
more likely to get you than incidental network maintenance in the raised 
floor environs.

Gerry
(Before I rediscovered numerical models of the environment, I was doing 
CFD on artificial heart designs.  And research on transplantation.  And 
space medicine.  The hours are better here.)
-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
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