Cancer Treatment

Three classes of carcinogens in human beings are (1) chemicals, (2) certain forms of radiation, and (3) viruses.

1. Chemicals
Scientists have identified many chemicals that can cause cancer in animals. These chemicals may also pose a cancer hazard to human beings. For example, cigarette smoke contains more than 4,000 chemical substances, of which dozens have been identified by scientists as carcinogens.

Some industrial chemicals create a cancer hazard for people who work with them. Such chemicals include aniline dyes, arsenic, asbestos, benzene, chromium, nickel, vinyl chloride, and certain products of coal, lignite, oil shale, and petroleum. Scientists work continuously to find chemicals that pose occupational cancer risks. Such identification can help ensure a safe workplace and identify substances that may also pose a risk to the general population.

Some substances that are added or applied to foods are also suspected of causing cancer in human beings. These substances include some chemicals used to control weeds and some that are used to kill insects. Government agencies regulate many of these substances, and, in some cases, prohibit their use. Molds that sometimes develop on such food crops as corn and peanuts may also contain carcinogens. The mold can be controlled through proper storage and handling of crops.

2. Radiation
Certain kinds of radiation can disrupt DNA and lead to cancer. X rays are a cancer hazard in large doses. However, doctors do not believe that routine medical and dental X rays pose a significant danger. A form of nuclear radiation known as ionizing radiation can also cause cancer. For example, in 1986, when Ukraine was part of the Soviet Union, a nuclear reactor at a power plant in Chernobyl exploded. Children who were exposed to radioactive fallout from that explosion have experienced an increased rate of thyroid cancer.

3. Viruses
Experiments have shown that certain kinds of viruses cause cancer in animals. Some viruses can also cause cancer in people. For example, the human papilloma virus causes most cases of cervical cancer. Another virus has been linked to a rare form of leukemia, and some forms of liver cancer may be caused by viruses. However, most experts feel that viruses are not a major cause of human cancers.