carcinogenic agents
A large number of agents cause genetic damage and induce neoplastic transformation of cells. They include (1) chemical carcinogens, (2) radiant energy, and (3) oncogenic viruses and some other microbes.
Radiant energy and some chemical carcinogens are documented causes of cancer in humans, and the evidence linking certain viruses to human cancers grows ever stronger.
Each group of agents is considered separately, but several may act in concert or synergize the effects of others.