Environmental factors are among the leading contributors to cancer risk. Every day, the average person encounters or uses many potentially hazardous substances that may contribute to various forms of cancer. These include:

• Tobacco smoke
• Radiation
• Infectious agents such as certain viruses
• Toxic chemicals or wastes

Substances that have been shown to lead to cancer are known as carcinogens. People may be exposed to carcinogens in their everyday environment inside and outside the home. Exposures that occur in the workplace are known as occupational risk factors.

Federal and international agencies are responsible for identifying and regulating the use of substances that may act as carcinogens. These organizations work to help protect the public from these potentially harmful substances and to thus reduce the overall incidence of cancers caused by environmental factors.