i searched google for creosote and cdc and found that you don't want it
in the garden at all.

"How can creosote affect my health?
Breathing vapors of the creosotes, coal tar, coal tar pitch, or coal
tar pitch volatiles can cause irritation of the respiratory tract.
Eating large amounts of creosote (any form) may cause a burning in the
mouth and throat and stomach pains. Eating large amounts of herbal
remedies containing creosote bush leaves may cause liver damage, while
large amounts of coal tar creosote may result in severe skin
irritation, eye burns, convulsions, unconsciousness, and even death."
so says
http://www.atsdr.cdc.gov/tfacts85.html
and the real long version is at:
http://www.atsdr.cdc.gov/toxprofiles...tml#bookmark06