Air quality--Dust

I was reading the latest DistLists and was interested to read about the
dust question.  I was surprised that "other organics" was so low
although relative to paper dust (in a library) maybe "other" is low.  My
surprise is because much of the content of house dust is sloughed off
skin cells (I'm still trying to find the reference that said that.  I
think it was in the CRC Handbook of Indoor Air Pollutants.) Anyway,
there isn't anything magic about the home so we tend to dump a lot of
skin cells off in the workplace too.  This is why we have dust mites.

I quote from Indoor Air Pollution Control:

    One of the most strongly allergenic materials found indoors is house
    dust, which is heavily contaminated with the fecal pellets of dust
    mites, the two most common species of which are Dermatophagoides
    pteronyssinus, the European dust mite, and Dermatophagoides farinae,
    more commonly found in North America.... It is also probably on of
    the most important causes asthma in North America, as well as the
    major cause of common allergies. ....

    Because of the large quantity of skin scales sloughed off daily by
    humans, mites have an abundant supply of food.  They cannot,
    however, eat 'fresh' skin scales.  Mites thrive best on skin scales
    that have been defatted. Some level of decomposition is essential
    before human skin scales can serve as mite food.  This decomposition
    or processing of skin scales into mite food is accomplished by mold
    species such as Aspergillus anastelodami.

Now granted, in the workplace there are many more sources of dust and
therefore maybe the "human" component is less important.

As for the abrasiveness of dust, it depends on where you are and how
outside dust gets inside.  For example, Dr. Klaus Hendriks commented on
the severity of dust problems when he was visiting photo collections in
Africa back in '85 or '86.  There the dust is so bad that Klaus
commented that everytime someone opened the door, dust was blowing in.
Considering the landscape, it is likely that the dust was largely
inorganic in nature and more likely to be abrasive.   Although I have no
research proof, looking at the lists of airborne pollutant dusts, the
organic materials listed all seem to be much less abrasive than
inorganics (generally).

I would suspect that if there was a lot of road construction going on
around the library, the inorganic (and likely more abrasive) dusts will
be more common in an air sample.  As for how abrasive dust can be,
consider the people with dirty cars (perhaps from driving on dusty
roads).  Most prefer to get the dirt off with water rather than wiping
the car (dry) for fear of scratching the paint.  (Alright, most of the
abrasive stuff is dried mud which is a little big to qualify as "dust"
:-) .)

One last point of interest about dust.  When I was discussing the use of
the diphenylamine test for identification of cellulose nitrate with the
objects conservators as the Royal Ontario Museum in Toronto, they
brought to my attention the fact that there is a problem with false
positive tests when the object is dusty.  Why?  Diphenylamine to
diphenylbenzidine violet has a reduction potential of about +0.76V (from
Volumetric Analysis, 2nd ed. vol. 1 by I.M Kolthoff and V.A. Stenger.)
This is slightly less than the conversion of Fe (III) to Fe (II) (at
+0.771 V) or Ag+ to Ag (+0.7996V). This means that the dust at the ROM
(and some other places I've talked to) has an oxidizing potential at
least as strong as Zn to Zn2+.  In absolute terms that may not be very
strong, but I must say that I was surprised.

-Doug

                                  ***
                  Conservation DistList Instance 5:53
                 Distributed: Saturday, April 25, 1992
                        Message Id: cdl-5-53-002
                                  ***