Peter,

Have you talked to your piano tuner? If s/he is a full fledged piano technician, as most seem to be, they'll be able to answer your questions accurately. I have read and re-read a small book about piano making and I saw nothing to suggest there is lasting negative environmental impact from it, as long as the foundry and string making were off-site.
    I would be more concerned with whether any other manufacturing took place in the building or on the site in a previous building.