Final answer:
Carcinogens are environmental agents that cause cancer by mutating DNA, with evidence of exposure coming from epidemiological studies and animal trials.
Step-by-step explanation:
Environmental agents that cause cancer are called carcinogens. Carcinogens cause cancer by producing mutations in DNA. Evidence for exposure to carcinogens come from epidemiological studies and animal feeding trials. These carcinogens can be chemical substances like tobacco smoke, asbestos, or benzene, environmental factors such as ultraviolet (UV) radiation, or biological agents like certain viruses. It's important to note that not every exposure to a carcinogen will result in cancer, as the effects can depend on individual susceptibility, the amount and duration of exposure, and other variables.