How likely is Lead to cause cancer?

We have no conclusive proof that lead causes cancer in humans.  Kidney tumors have developed in rats and mice that had been given large doses of some kind of lead compounds.  The Department of Health and Human Services (DHHS) has determined that lead and lead compounds are reasonably anticipated to be human carcinogens and the EPA has determined that lead is a probable human carcinogen.  The International Agency for Research on Cancer (IARC) has determined that inorganic lead is probably carcinogenic to humans and that there is insufficient information to determine whether organic lead compounds will cause cancer in humans.