This week, for the first time ever, viruses were added to the official list of known cancer-causing agents published by the National Institute of Environmental Health Sciences and the National Toxicology Program. Hepatitis B and C viruses, which can cause liver cancer, and some human papillomaviruses, which can cause cervical cancer, were added to the list. About 1 million people in the United States have chronic HBV infections, and 3 million are chronically HCV-infected. Both HBV and HCV can be transmitted through sexual contact, injection drug use, and blood transfusions. An estimated 20 million people in the United States have the sexually transmitted HPV, which often has no symptoms, and 5.5 million more are newly infected every year. Some strains of HPV have been linked with anal and penile cancer in men. As many has half of all sexually active gay men carry HPV; as many as 90% of HIV-positive gay men are coinfected with HPV.
Other carcinogenic agents newly listed in the report include X-rays and gamma radiation, with their risk of causing cancer depending "to some extent on age at the time of exposure"; heterocyclic amine compounds, found when meat and eggs are cooked or grilled at high temperatures and in cigarette smoke; naphthalene, an ingredient in mothballs and toilet bowl deodorants; lead used to make lead-acid storage batteries, ammunition, and cable coverings; and many chemicals used in textile dyes, paints, and inks. (Reuters, with additional reporting by Advocate.com)