WASHINGTON, Oct. 3 (UPI) -- Four new substances have been added to the official federal list of carcinogens, which is updated each year by the U.S. Department of Health and Human Services (HHS). Carcinogens are substances -- chemical, biological, and physical agents -- implicated in the direct causation of cancer, either by damaging the body's genome or altering cellular metabolism.
Of the four new substances, only one is classified as a "known human carcinogen." The other three were given the qualified classification of "reasonably anticipated to be human carcinogens."
The known carcinogen is ortho-toluidine, or o-toluidine, one of three toluidine isomers commonly used to sythensize rubber chemicals, pesticides, and dyes. Several studies have strongly linked the substance to bladder cancer. Ortho-toluidine was once only "reasonably anticipated" but is now "known" to cause cancer.
The other three newcomers -- which probably-almost-certainly cause cancer, too -- are the chemicals 1-bromopropane, cumene and pentachlorophenol. Not surprisingly, two of the four newly listed carcinogens (known and anticipated) can be found in tobacco smoke.
The organobromine compound 1-bromopropane is a colorless liquid that is used as a solvent in a number of commercial industries. It's often used in dry cleaning and to remove residues from optics, electronics and metals. When inhaled by rodents, the compound has been linked to tumors in the skin, lungs and digestive tract.
Cumene is a flammable, colorless liquid and a natural constituent of both crude oil and refined fuels. Inhalation of cumene fumes was shown to cause lung tumors in male and female mice, as well as liver tumors in female mice.
Pentachlorophenol (PCP) is a cocktail of chemicals commonly used as a pesticide, disinfectant and wood preservative. Though dangerous, the substance is remarkably effective. A telephone pole, for example, only lasts about seven years if untreated. If treated with PCP, the same pole can last upwards of 35 years. Those who work in wood production and wood treatment plants are most likely to be exposed to pentachlorophenol and its byproducts. One study found a link between non-Hodgkin lymphoma and human exposure to pentachlorophenol. Mice studies have also linked the substance to tumors in a variety of organs.
"Identifying substances in our environment that can make people vulnerable to cancer will help in prevention efforts," Dr. Linda Birnbaum, director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP), said in a recent press release accompanying the carcinogens report. "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."