environmental carcinogen /envī′rənmen″təl/ , any of the natural or synthetic substances that can cause cancer. Such agents may be divided into chemical agents, physical agents, hormones, and viruses. Some environmental carcinogens are arsenic, asbestos, uranium, vinyl chloride, ionizing radiation, ultraviolet rays, x-rays, and coal tar derivatives. Carcinogenic effects of chemicals may be delayed for as long as 30 years. Other carcinogens produce more immediate effects. Some studies indicate that the carcinogens in cigarette smoke are involved in 80% of all lung cancer. Most carcinogens are unreactive or secondary carcinogens but are converted to primary carcinogens in the body. Numerous factors, such as heredity, affect the susceptibilities of different individuals to cancer-causing agents.
