Any environmental factor that is capable of causing cancer is called a carcinogen. Many carcinogens are associated with human activity and lifestyle choices, including cigarette smoking, excessive alcohol use, poor diet, and lack of exercise. Other environmental factors, such as chemicals and radiation, are carcinogens as well. Some carcinogens are associated with specific types of cancer. For example, we know asbestos and smoking cause lung cancer and processed meats are linked with colon cancer.

How Carcinogens Cause Cancer

Almost every cell in the body has genes, which tell the cell what to do. Genes are made up of DNA. When carcinogens interact with DNA, they can cause genetic alterations, or mutations, which cells pass along as they divide. If one cell acquires enough mutations to become cancerous, it gives rise to subsequent cancer cells.

Two types of genes play a role in most cancers. Oncogenes are good genes (proto-oncogenes) gone bad. These mutations can stimulate the development of cancer. In contrast, and as their name suggests, tumor suppressor genes serve as brake pedals to prevent tumor growth. However, mutations in tumor suppressor genes prevent them from performing this function.

There are other types of cancer-related genetic mutations as well. Some mutations activate carcinogens; others prevent DNA repair genes from correcting errors that may arise when the cell duplicates.

Most cancers result from more than one type of genetic mutation.

How to Protect Yourself From Carcinogens

Research on the environmental causes of cancer is limited, so researchers really don't fully know the consequences of cumulative lifetime exposure to known carcinogens or how specific environmental contaminants interact with each other. What's more, the U.S. government does not generally require industries to prove the safety of their chemicals and products. Manufacturers have only tested a few hundred of the more than 80,000 chemicals in use.

In its 2008-2009 Annual Report, the President's Cancer Panel called the U.S.'s prevailing regulatory approach reactionary: "Instead of taking preventive action in the face of uncertainty about potential harms, a hazard must be 'incontrovertibly demonstrated' before we take action to eliminate or limit it."

This means individuals must do their best to protect themselves and their children (who are more susceptible to damage from environmental carcinogens) from exposure to known cancer-causing substances. Make wise lifestyle decisions (exercise, eat a healthy diet, don't smoke) and select personal care and other products with few or no carcinogens.

Rajiv V. Datta, MD, FRCS, FACS, FICS, reviewed this article.



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