Chemical carcinogens can be classified into one of four groups according to their chemical nature: organic carcinogens, inorganic carcinogens, fibers, and hormones.
Protecting yourself from these known carcinogens is the best way to reduce your cancer risk. But it doesn’t hurt to be careful when it comes to other potential dangers, Bevers says. Cell phones do emit a form of radiation. But Bevers says the type your phone puts out hasn't been shown to cause cancer. The Report on Carcinogens is a congressionally mandated, science-based, public health document that NTP prepares for the HHS Secretary. This cumulative report currently includes 248 listings of agents, substances, mixtures, and exposure circumstances that are known or reasonably anticipated to cause cancer in humans. Its carcinogen grouping system is the most widely used system. The organization has evaluated more than 1,000 likely cancer-causing agents and grouped them into one of four groups. IARC Carcinogen Classifications.
By the end of 2010, an estimated 569,490 Americans will have died from cancer. That's more than 1,500 people every day, and 1 out of every 4 deaths in this country [source: American Cancer Society]. So what is giving cancer such a push?
Well, as it turns out, in addition to cancer being hereditary, external factors are at play. For example, about 171,000 of this year's cancer deaths are believed to be caused by tobacco use [source: American Cancer Society]. How is it that external factors like tobacco use can have such a heavy hand in our cancer rates? It all comes down to carcinogens -- cancer-causing agents, like pollutants in the air, ultraviolet (UV) rays and viruses. How and why do carcinogens give cancer the upper hand?
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Carcinogens are typically any external causes of cancer, excluding those without a hereditary link. However, for the purpose of this article, we're referring to the following categories of carcinogens from the World Health Organization (WHO):
- Biological (e.g., types of bacteria)
- Chemical (e.g., chemicals in tobacco smoke and asbestos)
- Physical (e.g., UV radiation)
[source: World Health Organization]
Exposures to these 'agents of evil' can cause some wacky changes to our cells that lead to cancer. For example, some carcinogens can directly cause genetic mutations that foster abnormal cell growth and tumors. Others don't attack our genes directly, but trick our cells into cell division overdrive. That excess division then leads to potential genetic mutations down the road [source: American Cancer Society].
Does this mean that any exposure to a known carcinogen will cause you to develop cancer? The candid answer is, 'It depends.' For one, our genes are under continual attack by genetic mutations, but our DNA usually does a stellar job of repairing itself. That said, though, that 'repairman' skill isn't equal among all of us. Some of us do a better job of repairing our genes than others, which means that some people are more naturally susceptible to the negative effects of a carcinogen. Furthermore, a carcinogen's link to cancer can depend on:
- Age and gender
- Potency: Some carcinogens require pretty heavy exposure to be dangerous, while others are linked to cancer with just a brief exposure.
- Exposure type: For example, were you exposed to a carcinogen one time or continually over a period of years?
[source: National Cancer Institute]
If all of these factors have a role in just how much a carcinogen is linked to cancer, you may be wondering how you can determine what to look out for in your daily life. Or maybe you just want to know what known carcinogens even exist and how we find out about their danger. Advance to the next page to learn how we determine which substances to keep at arm's length.
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Imagine being on the team in charge of figuring out the known carcinogens around us. You wouldn't be able to wrap up your project all neat and tidy, filing it away marked complete. Instead, you would continue to research and refine your list, working on new revisions every couple of years. After all, your research would be linked to potentially preventing cancer, which is a matter of life and death.
In the last government report on carcinogens -- known as the '11th Report on Carcinogens (RoC)' -- 246 substances made it on the list. Of those substances, 58, such as alcoholic beverages, benzene, mustard gas and coal tars, were identified as known human carcinogens, while the other 188 were not as strongly labeled. Instead, they were referred to as 'reasonably anticipated' to be substances linked to cancer [source: National Toxicology Program].
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So just how does a substance make it on the list? Scientists rely on two different types of studies: lab and epidemiologic. In a laboratory environment, scientists are limited in what they can do, since they can't test on people. Therefore, they have to rely on cell cultures and animal testing. However, even that isn't enough because replicating exposures in people isn't possible, and it's impossible to say that a substance will act the same way in humans as it did in animals. Furthermore, to be able to use small sample groups, scientists must use doses markedly higher than human exposures when testing on animals. So scientists believe that positive carcinogen tests on animals are reasonable predictors of cancer risk and a justified reason to limit human exposure.
In contrast to laboratory studies, epidemiologic studies, also known as population-based studies, take research outside of the lab. In an epidemiologic study, researchers look at a population of people and target potential causes of cancer. The challenge here is that outside of the lab, scientists lose a controlled environment, meaning it's difficult to determine what someone is exposed to and when. Therefore, scientists aim to use the best of both worlds -- lab and epidemiologic studies -- to determine the carcinogens that are potentially life threatening.
And they're certainly life threatening, indeed. In fact, it's believed that 75 to 80 percent of cancer deaths in the United States are due to exposure to carcinogens rather than hereditary links to cancer [source: American Cancer Society]. However, that doesn't mean that we should all hide under a rock; there might be a carcinogen under that rock anyway. Instead, we can take a role in our own protection by limiting our contacts to known carcinogens. For example, staying away from tobacco, limiting alcohol consumption and avoiding too much sun exposure are all wise steps toward prevention. Just remember, keep your wits about you, and there are things you can do to stop some of those carcinogens in their tracks.
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Sources
- American Cancer Society. 'Cancer Facts & Figures 2010.' 2010. (Aug. 9, 2010) http://www.cancer.org/acs/groups/content/@nho/documents/document/acspc-024113.pdf
- American Cancer Society. 'Known and Probable Human Carcinogens.' (Aug. 9, 2010) http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/GeneralInformationaboutCarcinogens/known-and-probable-human-carcinogens
- National Cancer Institute. 'Cancer and the Environment.' September 1, 2006. (Aug. 10, 2010)
- National Toxicology Program. '11th Report on Carcinogens (RoC). (Aug. 31, 2010)http://ntp.niehs.nih.gov/index.cfm?objectid=E99AEB57-F1F6-975E-7BC5F9D939187D34
- World Health Organization. 'Cancer.' February 2009. (Aug. 9, 2010) http://www.who.int/mediacentre/factsheets/fs297/en/
What Are Carcinogens Definition
Four new substances have been added to a list of chemicals that may cause cancer compiled by the U.S. Department of Health and Human Services (HHS).
The list of known carcinogens now includes a chemical called ortho-toluidine, which is used to make rubber chemicals, pesticides and dyes. Recent research has linked the substance to bladder cancer in people.
Three other substances were added to a list of agents that are 'reasonably anticipated to be human carcinogens.' These include a cleaning solvent called 1-bromopropane, a wood preservative mixture known as pentachlorophenol and cumene, which can be found in fuel products and even tobacco smoke. [12 Worst Hormone-Disrupting Chemicals & Their Health Effects]
'Identifying substances in our environment that can make people vulnerable to cancer will help in prevention efforts,' Linda Birnbaum, director of the National Institute of Environmental Health Sciences and the National Toxicology Program, said in a statement. 'This report provides a valuable resource for health regulatory and research agencies, and it empowers the public with information people can use to reduce exposure to cancer-causing substances.'
Ortho-toluidine was originally classed as 'reasonably anticipated' to be a human carcinogen in 1983. But HHS scientists re-evaluated the substance, looking at three studies of dye workers and two studies of rubber-chemical workers who were regularly exposed to ortho-toluidine. They found enough evidence of a link between ortho-toluidine exposure and an increased risk of bladder cancer to call the chemical a known carcinogen, according to HHS. Rats also developed bladder tumors after they ingested ortho-toluidine.
Ortho-toluidine is no longer produced in the United States, but at least 1 million lbs. (450,000 kilograms) of the substance is imported into the country each year, according to HHS. The people who have the greatest risk of exposure are employees who work in chemical plants where ortho-toluidine is used to make rubber chemicals, dyes and pesticides.
HHS officials said they didn't have enough evidence to definitively prove that exposure to the other three chemicals can cause human cancers. But these substances do cause rats and mice to develop tumors, according to the agency.
In experiments, rodents that inhaled fumes of 1-bromopropane — a colorless to light yellow liquid solvent — developed tumors in several organs, including their skin, lungs and large intestine. The substance is used as a cleaner for optics, electronics and metals. It has also become popular in dry cleaning as a replacement for perchloroethylene, another chemical considered a health and environmental hazard.
Mice that inhaled cumene fumes developed lung tumors and liver tumors, according to HHS's review. The flammable liquid with a gasoline-like odor is found in coal tar and petroleum, as well as tobacco smoke. It is used primarily to make acetone and phenol.
Pentachlorophenol — a substance used to treat utility poles, wood pilings and fence posts — caused tumors in the liver and other organs of mice. In small studies of humans, exposure to this compound was associated with an increased risk of the blood cancer non-Hodgkin lymphoma, but the HHS said it considered the evidence too limited to call pentachlorophenol a known carcinogen.
Group 4 Carcinogen
The HHS's 13th Report on Carcinogens, which now includes 243 listings total, is available online:http://ntp.niehs.nih.gov/pubhealth/roc/roc13/index.html
List Of Common Carcinogens
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