The Report on Carcinogens (RoC) is a scientific and public health document that provides information about the relationship between the environment and cancer. It is a congressionally mandated report (Section 301 (b) (4) of the Public Health Service Act) that identifies agents, substances, mixtures, or exposures (collectively called substances) that may potentially put people in the United States at an increased risk for cancer. Listed in the RoC are a wide range of substances, including metals, pesticides, drugs, and natural and synthetic chemicals.
The listings in the RoC identify a substance or exposure circumstance as a known or reasonably anticipated human carcinogen. The RoC is a hazard identification document and does not present quantitative assessments of the risks of cancer associated with exposure to these substances. Thus a listing in the RoC only indicates a potential hazard and does not estimate cancer risks to individuals associated with exposures in their daily lives.
The full report is available at http://ntp.niehs.nih.gov/go/roc13.
The NTP prepares the RoC for review and approval by the Secretary of U.S. Department of Health and Human Services. The RoC can be used by regulatory agencies and others for decision-making.
Agents, substances, mixtures, or exposures, collectively called substances, can be listed in the RoC, either as known to be a human carcinogen or as reasonably anticipated to be a human carcinogen. See http://ntp.niehs.nih.gov/go/15209 for specific listing criteria.
Known to be a human carcinogen
This category is used primarily when there is sufficient evidence of cancer from human studies showing a cause-and-effect relationship between exposure to the substance and human cancer. Occasionally, substances are listed in this category based on human studies showing that the substance causes biological effects known to lead to the development of cancer.
Reasonably anticipated to be a human carcinogen
This category includes substances where there is limited evidence of cancer in humans, or sufficient evidence of cancer in experimental animals, showing a cause-and-effect relationship between exposure to the substance and cancer. Alternatively, a substance can be listed in this category, if there is evidence that it is a member of a class of substances already listed in the RoC or causes biological effects known to lead to the development of cancer.
Expert, scientific judgment, with consideration given to all relevant information, is used to review all cancer studies and to reach conclusions.
Anyone can nominate a substance to NTP for consideration of its listing in, or removal from, the RoC by using the form found at http://ntp.niehs.nih.gov/go/nominateroc.
A formal evaluation is conducted for the nominated substances, and candidate substances are selected to proceed through the scientific review process (http://ntp.niehs.nih.gov/go/15208).
The evaluation of each substance follows a multi-step process with multiple opportunities for scientific and public input. Established listing criteria are used to evaluate the scientific evidence on each substance. For more detailed information, see http://ntp.niehs.nih.gov/go/15208.
A listing in the RoC does not by itself mean that a substance will cause cancer. Many factors, including the amount and duration of exposure, and an individual’s susceptibility to a substance, impact whether a person will develop cancer or not.
For each listed substance, the RoC provides information from cancer studies that support the listing, as well as information about potential sources of exposure and current federal regulations to limit exposures. Substance profiles for each substance are found at http://ntp.niehs.nih.gov/go/roc13.
Where possible, individuals should try to limit their exposure to the substances listed in this report. If you have questions or concerns about current or past exposures to any of these substances, the information developed by the National Institutes of Health can help you to become better informed. Discuss these fact sheets and what you have learned with your health care providers. Another good resource is the Association of Occupational and Environmental Clinics (AOEC). The AOEC has a network of clinics across the country dedicated to the prevention and treatment of occupational and environmental illnesses.
1-Bromopropane is used as a solvent, for cleaning or adhesives, in a variety of industrial sectors, including spray adhesives (e.g., in foam cushion manufacturing), vapor degreasing (e.g., to clean optics, electronics, and metals), aerosol solvents (e.g., aircraft maintenance), and dry-cleaning (e.g., textile solvent).
1-Bromopropane is listed as reasonably anticipated to be a human carcinogen.
People are primarily exposed to 1-bromopropane by inhalation or through the skin in workplaces that use or produce 1-Bromopropane. The highest levels of exposure occur among sprayers in the spray adhesive industry. There is very little data available on how people may be exposed to 1-bromopropane in their everyday lives.
Studies have shown that 1-bromopropane caused neurological effects in humans, and cancer and toxic effects (neurological, reproductive, and liver) in experimental animals. Some agencies have issued hazard alerts for workers.
The Occupational Safety & Health Administration (OSHA) has not established a regulatory exposure standard for 1-bromopropane.
Human Studies: No human studies were identified that evaluated the relationship between human cancer and exposure specifically to 1-bromopropane.
Animal Studies: In rodents, inhalation exposure to 1-bromopropane caused tumors in several different organs, including the skin, lungs, and large intestine.
Mechanistic Studies: Exactly how 1-bromopropane causes cancer is not fully known. However, exposure to 1-bromopropane has been shown to cause biological changes that relate to cancer development, including DNA damage and mutations, changes to the body’s immune system, antioxidant depletion, and buildup of toxic reactive oxygen species in the body.
Cumene is used primarily to manufacture phenol and acetone, which are chemicals used widely in industry and in some consumer products.
Cumene is listed as reasonably anticipated to be a human carcinogen.
People are exposed to cumene by inhaling it in workplaces that produce or use cumene, and in gasoline-transport-related jobs. People can also be exposed to cumene in their everyday lives from breathing in petroleum and petroleum emissions, and from cigarette smoke.
Human Studies: No human studies were identified that evaluated the relationship between human cancer and exposure specifically to cumene.
Animal Studies: Inhalation exposure to cumene caused benign and malignant lung tumors in male and female mice, and liver tumors in female mice.
Mechanistic Studies: The exact mechanism of how cumene causes cancer is not fully known. There is evidence that humans and experimental animals metabolize cumene through similar metabolic pathways. Exposure to cumene in laboratory animals caused DNA damage in some tissues.
Pentachlorophenol and by-products of its synthesis are a mixture of chemicals primarily used as a wood preservative. Since 1984, it has been regulated in the United States as a restricted-use pesticide for commercial use. It is mainly used to treat utility poles.
NTP decided to evaluate pentachlorophenol and by-products of its synthesis together because virtually everyone who is exposed to pentachlorophenol is also exposed to by-products of its synthesis.
Pentachlorophenol and by-products of its synthesis is listed as reasonably anticipated to be a human carcinogen.
Although its uses are restricted, exposure to this wood preservative is still a concern. People can be exposed to pentachlorophenol and by-products of its synthesis by breathing contaminated outdoor or indoor air or indoor dust, from the soil, or by ingesting water or food that may be affected by it. Children who play in contaminated soil may be particularly vulnerable. People who worked with pentachlorophenol and by-products of its synthesis in workplaces that produced it or treated wood with it, or are in contact with the treated wood likely had more exposure.
Pentachlorophenol and by-products of its synthesis caused adverse health effects (cancer, liver, immunological) in experimental animals, and possibly non-Hodgkin lymphoma in humans and other immunological effects.
Human Studies: Studies of sawmill workers and pentachlorophenol production workers have found a positive association between exposure to pentachlorophenol and non-Hodgkin lymphoma. However, due to the small number of studies, there is no definitive link showing exposure to pentachlorophenol causes cancer in humans.
Animal Studies: Exposure to pentachlorophenol caused tumors in the liver, adrenal gland, and blood vessels in mice. Male rats exposed to pentachlorophenol had increased incidences of tumors in the nose and tunica vaginalis, the membrane that covers the testis.
Mechanistic Studies: The exact mechanism of how pentachlorophenol causes cancer is not fully known. Pentachlorophenol or its metabolites may cause DNA damage, immune suppression, and inhibition of apoptosis, or cell death.
o-Toluidine is used to make rubber chemicals and intermediates to dyes or herbicides.
o-Toluidine is listed as a known human carcinogen.
People who work in places that use o-toluidine have the highest exposure through inhalation or through the skin. People are exposed to lower levels of o-toluidine in their everyday lives from consumer products (such as o-toluidine based dyes), medical products (such as the anesthetic prilocaine used in dental procedures), cigarette smoke, and possibly the environment when o-toluidine is released into air, land, or water through its production and use.
o-toluidine causes urinary bladder cancer in humans.
Human Studies: The association between urinary bladder cancer and exposure to o-toluidine has been studied in rubber chemical workers and dye workers. These studies show that o-toluidine exposure causes urinary bladder cancer in humans.
Animal Studies: Similar to humans, rats developed urinary bladder tumors after ingesting o-toluidine. Exposure to o-toluidine also caused tumors of the connective tissue; subcutaneous tissue, or deepest layer of the skin; mesothelium, or tissue that surrounds certain organs and forms the lining of certain body cavities. Mice that were exposed to o-toluidine developed tumors in blood vessels and the liver.
Mechanistic Studies: Cancer formation may be related to o-toluidine being metabolized and transformed in the body to become more bioactive and toxic. o-Toluidine, primarily via its metabolites, may also cause DNA damage, chromosomal damage, and mutations that lead to cancer. Importantly, these studies provide evidence that the mechanisms by which o-toluidine causes cancer in rodents are likely to occur in exposed humans.