[Cob] Tires For a Foundation? what about toxic off-gassing?

[ocean]

I know why folks like to build with used tires, but I'm very concerned 
about toxic off-gassing.  Used tires have absorbed lots of oil and 
gasoline from the highways, which will outgas over time.  Especially if 
we build a "tight" solar heated home, with very little ventilation.

What do you all think?

Ocean Liff-Anderson
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Steward, Ahimsa Sanctuary  http://www.peacemaking.org
Proprietor, Intaba's Kitchen  http://www.intabas.com