Source: German Varnish Making by Professor Max Bottler of Würzburg, Authorized translation with Notes on American Varnish and Paint Manufacture by Alvah Horton Sabin, M.S. First Edition, 1912, John Wiley & Sons, London:

It just "happened" to be on my bookshelf, but it took a while to find.

The balsams used in that era were largely "natural" tree products, probably not particularly "toxic" although individual sensitivities vary. In their natural state, most of these are "bio-degradable," although incorporation into lacquers and varnishes may make them rather persistent, especially if bound in soil.

Resins used in many lacquers and varnishes of the era share the "natural" origin and characteristics of the balsams, although benzoin – a natural but currently restricted material(?) – was used "as a perfume and to give lustre."

Color resins constituted a distinct class of resins, and include some irritants, but few that would appear to be persistent toxins.

In some varnishes and lacquers, significant amounts of natural asphalt, coal-tar pitch, caoutchouc, vulcanized rubber, pyroxylin, nitrocellulose, and celluloid were used.

Drying oils, principally linseed oil, were largely plant products, although a number of less-used ones were known to be "irritants."

Turpentine, rosin-spirit, petroleum, benzine (petroleum-ether), benzole (coal-tar benzine), chlorbenzol, ethyl and methyl alcohol, ether, acetone (dimethyl ketone) methyl-ethyl-ketone, acetylene tetrachloride, cabon tetrachloride, carbon bisulphide, and chlorhydrin are listed as common process materials and as constituents of varnishes of the time.

Coal-tar colors, later found to be mostly carcinogens, were used in substantial quantities, along with lampblack and mineral colors. Historically, the development in Germany of these coloring agents in the late 1800s was responsible for German "experts" dominating the worldwide market for dyes and pigments through the early to mid part of the 1900s.

"Chemical products" required for making varnish are listed separately, and include litharge, red lead, orange lead, sugar of lead, lead resinate, lead linoleate; manganese suboxide, hydroxide, and dioxide, resinate of manganese, linoleate of manganese; resinate of lead and manganese resinate of zinc.

A quick look at the specific formulas in common use indicates that the lead and manganese materials were used frequently in processing of varnishes and lacquers and of constituent materials, even where they were not considered an "ingredient" in the finished product.

While it is unlikely that a piano manufacturer would have made his own varnishes, the same solvents used in manufacture were commonly used, as thinners and cleaning agents, by "end users" of these products. It is likely that large quantities of benzine, MEK, carbon bisulphide, carbon tetrachloride, and a few other "nasties" were kept, used, and dumped at any such facility.

Sorry, but it's been too long since I read the whole book to make more specific extracts. Note that names and spellings commonly used now may differ from what's in the books of the era.

The number of toxic and volatile constituents of varnishes in use in the period in question makes it almost certain that there is at least some local contamination remaining, although such "opining" can't be a proper substitute for an actual soil test.

John