Cancer-causing substances update

For the first time, the US government has added certain viruses to its list of things that can cause cancer in humans. Hepatitis B, hepatitis C, and some human papilloma viruses (HPV) are among the 17 new entries on the Department of Health and Human Services' Eleventh Edition of the Report on Carcinogens.

The list, which is updated every two years, now details 58 substances that are known to cause cancer in humans, and 188 substances "reasonably anticipated" to do so.

Six new known carcinogens were added in the latest update. Hepatitis B and C were included because they cause liver cancer. Several types of HPV cause cervical cancer.

"These viruses are important causes of cancer," said Elizabeth Ward, PhD, director of surveillance research for the American Cancer Society.

The most recent ACS report on cancer in the US, Cancer Facts & Figures 2005, highlighted these and several other cancer-causing viruses because of their impact on cancer worldwide.

The report estimates that there will be 667,000 new cases of liver cancer worldwide in 2005. Of those, 35% will be caused by chronic infection with hepatitis B and 23% will be caused by chronic infection with hepatitis C. HPV is considered the main cause of the 490,000 new cases of cervical cancer that occur worldwide each year.

Gamma radiation and X-rays were also added to the list of known carcinogens because they can cause leukemia and cancers of the thyroid, breast, and lung, as well as other types of cancer. Most people are exposed to this type of radiation from medical procedures or by exposure to natural sources like radon, a gas that filters up through the ground. Radiation from neutrons, which penetrates the Earth's atmosphere from space, is also now part of this list. Neutron radiation causes genetic damage similar to that caused by x-rays and gamma rays and can cause the same types of cancer.

Lead, Meat Compounds, Industrial Chemicals Suspect

Most of the 11 new substances added to the list of things that probably cause cancer are chemicals used in industrial processes or manufacturing. These substances -- naphthalene, cobalt sulfate, nitrobenzene, nitromethane, and the dye ingredients 1-amino-2, 4-dibromoanthraquinone and 4,4-thiodianiline -- have been shown to cause cancer in animals. Another dye compound, diazoaminobenzene, causes genetic damage in animals. In the human body, it changes into benzene, a substance known to cause cancer in people.

The other new substances on this list, however, are more commonly found throughout the environment. Lead is now officially considered a compound that might cause cancer in people because it is known to cause kidney, brain, and lung cancer in animals. Lead is used to make some batteries, ammunition, and cable coverings, and may be found in paints, glass, ceramics, fuels, and even some cosmetics. People are exposed to lead by swallowing or breathing it.

"In years past, when lead was added to gasoline, this was the major source of exposure," Ward explained. "More recently, since lead has been taken out of gasoline, the major source of exposure has been old lead-containing paint, which can be found in older homes and on structures such as bridges."

Although the amount of lead used in paint has been regulated since 1979, Ward said, millions of homes in the United States still have lead paint. During renovation of an older home, swallowing or breathing lead paint dust can increase your body’s lead content. Children may chew or swallow chips of this old paint. More often, normal wear and tear adds particles of paint to soil and household dust, and children unintentionally swallow lead from their contaminated toys or hands.

Tap water that runs through lead pipes and soldered joints in older homes can also be contaminated with lead.

The US Environmental Protection Agency has information on testing your home for lead and getting it removed.

The final addition to the probable carcinogen list is a collection of compounds that form in meat when it is grilled or cooked at high temperatures. MeIQ, MeIQx, and PhIP are known as heterocyclic amine compounds; they can cause cancer in animals. Some studies suggest that consumption of meat cooked at high temperatures increases risk of colon cancer and breast cancer in humans.

Because of this link, ACS dietary guidelines recommend cooking meat at lower temperatures -- such as by baking, broiling, or poaching it -- rather than charbroiling or frying it.

"Although it is not possible to predict with complete certainty from animal studies which exposures will cause cancer in humans," Ward said, "it is prudent to treat substances that cause cancer in laboratory animals as if they pose a hazard to humans."

http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Viruses_Added_to_List_of_Cancer-Causing_Substances.asp