Too much exposure to ultraviolet radiation, however, is one of leading causes of cancer. This is particularly true of skin cancer in humans. Other forms of radiation include cosmic rays, x-rays, and the emissions of radioactive materials. They also produce mutagenic effects.
People have created other mutagens that are now in the earth’s environment. Many industrial chemicals change genetic sequencing by changing the nucleotides of DNA. The first chemical mutagen discovered was mustard gas. Mustard gas was developed during World War I as a way to kill the enemy.