Jesse and RadSafers, EPA cancer slope factors for various chemicals are provided at the following site: http://www.epa.gov/ngispgm3/iris/subst-fl.htm I too agree that the use of these extrapolations at low chemical exposure levels (e.g., water and air standards, Superfund clean-ups) causes a lot of money to be spent with little apparent societal benefit... Regards, Scott Sorensen ssorensen@doeal.gov