Sassman wrote:
Thanks. Does someone know how plant roots interact with creosote
treated wood. I suppose the creosote
is coal tar based and contains benzene and other carcinogens. But to a
plant, would creosote be a good
additive to a alkali soil making it more acidic. And would the plant
be free of any carcinogens.

I have rows of old railroad ties and the trees along these two rows
have performed the best in growth
compared to other saplings, especially the pine trees and the grape
vine.

I suspect that the nice growth of plants near the railroad ties is due
to factors not related to chemicals. Maybe drainage, shading, or a
different soil type in this area? The amount of chemicals that will
leach from the treated wood will decrease over time as more water
soluble and/or biodegradable species go away. Those compounds left in
the wood are insoluble and hence cannot get out of the wood. My only
concern about carcinogens in the plants would be chromium. If you have
chromium treated wood there, it may be a problem if you plant to eat the
plants.
---
www.analyticalchem.com

I doubt that chromium is in that wood at all if it really was intended
for railroad ties. Chromium compounds are too expensive for the large
number of ties that railroads use. It is almost certainly some kind of
creosote type preservative. As for the carcinogens thus contained they
will have been exposed to a long amount of oxidation by air, UV
radiation, and leaching by rain that would diminish such materials
considerably.
FK