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

[David Mathog]

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.

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.

Regards,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech