What are carcinogens? Give two examples. Why the disease caused by them is so much dreaded?

A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis, the formation of cancer.

Examples include X-rays, UV radiations, tobacco smoke (contains chemical carcinogens)

Disease caused by them is much-dreaded because cancer is an uncontrolled proliferation of the cells. Uncontrolled growth forms masses of cells called tumors.