There is currently a thread in the Piporg-L list that's focusing on the
effects of air pollution on NYC pipe organs. Here are two snippets from
one posting, the second of which would effect pouches in a player piano:

"A number of samples of destroyed leather were removed from New York City organs,
and were for the most part left on their pouch rails or blocks for a
more thorough examination. Two things were brought out by the examiners -
first, that it seemed that where there was actual deterioration of newer
leather (as opposed to the natural attrition of the older stuff) the
blowers of the organs experiencing this were more likely to be pumping
sewer gas from the basements up into the chestwork ...

" ... more to the point,  a number of samples were showing circular
leather pouches which were tearing around their circumferences, not
crumbling or rotting.  The leather itself was quite decent - but the
problem lay in faulty releathering technique!  When the glue to attach
pouches to their boards or blocks is allowed to come to close to the
edge of the pouch cavity, over which the leather must flex when it
collapses, the dried glue can form almost a 'knife edge' which because
of the 'slamming down' of the pouch when it is collapsed can ultimately
begin to cut through the rather thin leather - and it weakens on those
circular creases until it begins to separate.  Unless the edges of the
pouch cavities are radiused, or the glue kept well back, this failure
can happen even where the air quality is as sweet as in a woodland glen."

- Karl Ellison
  Ashland, Massachusetts

P.S. I've added more RealAudio Piano Rolls to my Webpage:

           http://members.aol.com/kbellison/kbe.html