List of Cancer-Causing Agents Grows
Research Triangle Park, N.C. – The Department of Health
and Human Services released its Eleventh Edition of the Report
on Carcinogens today, adding seventeen substances to the growing
list of cancer-causing agents, bringing the total to 246. For the
first time ever, viruses are listed in the report: hepatitis B
virus, hepatitis C virus, and some human papillomaviruses that
cause common sexually transmitted diseases. Other new listings
include lead and lead compounds, X-rays, compounds found in grilled
meats, and a host of substances used in textile dyes, paints and
“Among U.S. residents, 1 in 2 men and 1 in 3 women will
develop cancer at some point in their lifetimes. Research shows
that environmental factors trigger diseases like cancer, especially
when someone has a family history,” said Kenneth Olden, Ph.D.,
director of the National Institute of Environmental Health Sciences
and the National Toxicology Program, which prepared the report
The Report on Carcinogens, Eleventh Edition, referred to as the “RoC,” lists
cancer-causing agents in two categories “known to be human
carcinogens” and “reasonably anticipated to be human
carcinogens.” The report now contains 58 “known” and
188 “reasonably anticipated” listings. Federal law
requires the Secretary of the Department of Health and Human Services
to publish the report every two years.
Six substances have been added to the “known” category:
Hepatitis B virus (HBV) and hepatitis C virus (HCV) are viruses
that cause acute or chronic liver disease. They are listed in the
report as “known human carcinogens” because studies
in humans show that chronic hepatitis B and hepatitis C infections
cause liver cancer. Approximately one million United States residents
are chronically infected with HBV, which primarily is transmitted
through sexual contact (50%) and intravenous drug use (15%).
HCV is the leading cause of liver disease in the United States
with more than three million people infected. The major risk factor
for hepatitis C infection is illegal intravenous drug use, which
accounts for 60 percent of acute infections in adults. The incidence
of both hepatitis B and hepatitis C infections is decreasing among
United States residents. A vaccine is available for preventing
hepatitis B infection but not hepatitis C infection. Infections
can also be prevented by screening blood supplies, and by reducing
contact with contaminated fluids in health care settings.
Human papillomaviruses (HPVs) are viruses that are sexually transmitted
and can infect genital and mucous membranes. Some of these genital
mucosal type HPVs are listed in the report as “known human
carcinogens” because studies show they cause cervical cancer
in women. Approximately 20 million people in the United States
are infected with genital HPVs, and 5.5 million new infections
occur each year. Most people infected do not have symptoms, but
some develop genital warts or cervical abnormalities.
X-radiation and gamma-radiation are listed in the report as “known
human carcinogens” because human studies show that exposure
to these kinds of radiation causes many types of cancer including
leukemia and cancers of the thyroid, breast and lung. The risk
of developing cancers due to these forms of ionizing radiation
depends to some extent on age at the time of exposure. Childhood
exposure is linked to an increased risk for leukemia and thyroid
cancer. Exposure during reproductive years increases the risk for
breast cancer, and exposure later in life increases risk for lung
cancer. Exposure to X-radiation and gamma radiation has also been
shown to cause cancer of the salivary glands, stomach, colon, bladder,
ovaries, central nervous system and skin.
Of the total worldwide exposure to X-radiation and gamma-radiation,
55 percent is from low-dose medical diagnosis such as bone, chest
and dental X-rays, and 43 percent is from natural sources like
radon. Other sources, such as industry, scientific research, military
weapons testing, nuclear accidents and nuclear power generation,
account for about 2 percent.
Neutrons are also listed in the report as a “known human
carcinogen.” They cause genetic damage similar to that of
X-radiation and gamma radiation, and thus can cause the same cancers.
Neutron radiation is used less than other types of radiation in
industry, medicine, and research. The general population is exposed
to neutrons primarily from cosmic radiation that penetrates the
Eleven substances have been added to the “reasonably anticipated” category:
Naphthalene is used as an intermediate in the synthesis of many
industrial chemicals, and has been used as an ingredient in some
moth repellants and toilet bowl deodorants. Naphthalene is listed
in the report as “reasonably anticipated to be a human carcinogen,” based
on inhalation studies in animals which showed it causes rare nasal
tumors in rats and benign lung tumors in female mice.
MeIQ, MeIQx, and PhIP are heterocyclic amine compounds formed
when meats and eggs are cooked or grilled at high temperatures.
These compounds are also found in cigarette smoke. They are listed
in the report as “reasonably anticipated to be human carcinogens” because
oral studies in animals showed they caused cancer in multiple organs
including the forestomach, colon, liver, oral cavity, mammary gland,
skin, and cecum. Several human studies suggest there is an increased
risk for breast and colorectal cancers related to consumption of
broiled or fried foods that may contain these or other similar
MeIQ is 2-Amino-3, 4-dimethylimidazo [4,5-f]quinoline
MeIQx is 2-Amino-3, 8-dimethylimidazo [4,5-f]quinoxaline
PhIP is 2-Amino-1-methyl-6-phenylimidazo [4,5-b]pyridine
Lead is used to make lead-acid storage batteries, ammunition,
and cable coverings. Lead compounds are used in paint, glass and
ceramics, fuel additives, and in some ethnic and ceremonial cosmetics.
The report lists lead and lead compounds as “reasonably anticipated
to be human carcinogens” because exposure to lead or lead
compounds is associated with a small increased risk for lung or
stomach cancer in humans, and cancer of the kidney, brain or lung
in studies with laboratory animals.
Cobalt Sulfate is used in electroplating, as coloring agents for
ceramics, and as drying agents in inks and paints. Cobalt sulfate
is listed as “reasonably anticipated to be a human carcinogen” based
on inhalation studies in laboratory animals that showed it causes
adrenal gland and lung tumors.
Diazoaminobenzene is a chemical used as an intermediate in the
production of dyes and to promote adhesion of natural rubber to
steel. Diazoaminobenzene is listed as “reasonably anticipated
to be a human carcinogen” based on evidence that it is metabolized
to benzene, a “known human carcinogen,” and because
it causes genetic damage in laboratory animals.
Nitrobenzene is a chemical used mainly in the production of other
industrial chemicals. It is listed as “reasonably anticipated
to be a human carcinogen” because inhalation studies of this
compound produced cancer in experimental animals.
1-Amino-2, 4-dibromoanthraquinone is a vat dye that is used in
the textile industry. It is listed as “reasonably anticipated
to be a human carcinogen” based on evidence that it causes
cancer in experimental animals.
4,4’-Thiodianiline has been used as an intermediate in the
preparation of several kinds of dyes. It is listed as “reasonably
anticipated to be a human carcinogen” based on evidence that
it causes cancer in experimental animals.
Nitromethane is used in specialized fuels, explosives, and in
the synthesis of pharmaceuticals and agricultural chemicals. It
is listed as “reasonably anticipated to be a human carcinogen” based
on evidence that it causes cancer in experimental animals.
The Report on Carcinogens, Eleventh Edition, is prepared by the
National Toxicology Program, an interagency group coordinated by
the U.S. Department of Health and Human Services. The full report
is available at the NTP website http://ntp.niehs.nih.gov.
The National Toxicology Program is located at the National Institute
of Environmental Health Sciences (NIEHS) in Research Triangle Park,
NC. Part of the National Institutes of Health, NIEHS looks at factors
in the environment that may be harmful to human health.