I cannot agree with Dr. Coyner more. Inducing cancer in lab animals is only done under high levels of scientific scrutiny and regulation and at authorized facilities by properly educated scientists and a known beneficial outcome for science. Today the movement is toward non animal models so that even lab rats do not have to suffer. No veterinarian in our group is going to advise you on this as it appears mis-guided.
Lead toxicity causes neurologic disease, gastrointestinal disease, and hematologic abnormalities, it is not commonly considered a carcinogen. Frankly, if you don't know what chemicals are carcinogens, and are unable to do the appropriate scientfic research to establish this prior to starting this study (asking these kind of questions on an intenet forum is not appropriate or scientific) then you should not be performing this reseach at all. It sounds like you are wanting to induce cancer in rats for the sake of getting a grade on a paper, which is not an appropriate use of laboratory animals; they should never be used for casual purposes, and as our science progresses and we can find out the answers we need to know in a way that does not destroy animals, hopefully we will not need to use laboratory animals at all.
Kimberly Coyner, DVM DACVD