Carcinogens are substances capable of causing cancer in living tissue, and there are hundreds of compounds currently in use that the government considers carcinogens or possible carcinogens. Ever so often, experts take a fresh look at the substances being used and the research involving them, making the carcinogen list even longer.
“Substances and exposures that can lead to cancer are called carcinogens. Some carcinogens do not affect DNA directly, but lead to cancer in other ways. For example, they may cause cells to divide at a faster than normal rate, which could increase the chances that DNA changes will occur,” states the American Cancer Society.
“Carcinogens do not cause cancer in every case, all the time. Substances labeled as carcinogens may have different levels of cancer-causing potential. Some may cause cancer only after prolonged, high levels of exposure. And for any particular person, the risk of developing cancer depends on many factors, including how they are exposed to a carcinogen, the length and intensity of the exposure, and the person’s genetic makeup.”
Because it is not considered ethical to test compounds on people to see if they cause cancer, it can be difficult to maintain a complete list of carcinogens at all times. Substances on the list are placed there based on case reports and scientific studies conducted on laboratory animals.
This month, the U.S. Department of Health and Human Services (HHS) has added 4 substances to the carcinogen list, including: ortho-toluidine, used to make rubber chemicals, pesticides and dyes; 1-bromopropane, used as a cleaning solvent and spray adhesive; cumene, used to make phenol and acetone, and also found in fuel products and tobacco smoke; and the wood preservative mixture pentachlorophenol.
“Identifying substances in our environment that can make people vulnerable to cancer will help in prevention efforts, said Linda Birnbaum, Ph.D., director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP) 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.
Of the four items added to the list, only ortho-toluidine has been added as a “known carcinogen,” meaning research clearly shows this substance has cancer-causing characteristics. 1-bromopropane, cumene and pentachlorophenol have been added as “anticipated human carcinogens,” meaning there is enough data to reasonably assume these substance will cause cancer from prolonged or excessive exposure.
“Since 1983, ortho-toluidine has been listed in the Report on Carcinogens as reasonably anticipated to be a human carcinogen. However, new cancer studies led NTP to reevaluate and reclassify ortho-toluidine, and it is now added to the category of known to be a human carcinogen, based on studies in humans showing it causes urinary bladder cancer,” states HHS.
1-bromopropane, cumene and pentachlorophenol have no human studies to back them up, but all three have been shown to cause cancer in laboratory mice.