New Federal “Report on Carcinogens” Lists Steroidal Estrogens Used in Estrogen Replacement Therapy to List of Known Human Carcinogens

Dec 11, 2002 (Washington, DC) The federal government today published its biennial “Report
on Carcinogens”, adding steroidal estrogens used in
estrogen replacement therapy and oral contraceptives to its
official list of “known” human carcinogens. This and 15
other new listings bring the total of substances in the
report, “known” or “reasonably anticipated” to pose a
cancer risk, to 228.

This, the tenth edition of the report, was forwarded to
Congress and released to the public today by the Department
of Health and Human Services. It was prepared by the
National Toxicology Program, an arm of the HHS located at
the National Institute of Environmental Health Sciences,
one of the National Institutes of Health. The reports are
published every two years after lengthy study and
scientific reviews by three successive expert panels of
government and non-government scientists.

In a statement releasing the report, HHS Secretary Tommy
Thompson today thanked “the hundreds of scientists who have
contributed to this report through their original research
or their careful reviews of these important studies. The
public is well served by this dispassionate report that
helps all of us ensure that the American public is made
aware of potential cancer hazards.”

The tenth report newly lists the group of hormones known as
steroidal estrogens as “known human carcinogens.” A number
of the individual steroidal estrogens were already listed
as “reasonably anticipated carcinogens” in past editions,
but this is the first report to so list all these hormones,
as a group. As with all the other medications listed, the
“Report on Carcinogens” does not address or attempt to
balance potential benefits of use of these products.

Also newly listed as “known” causes of cancer in humans are
broad spectrum ultraviolet radiation, whether generated by
the sun or by artificial sources; wood dust created in
cutting and shaping wood; nickel compounds and beryllium
and its compounds commonly used in industry. Beryllium and
beryllium compounds are not new to the list but was
previously listed as “reasonably anticipated to be a human

The report is mandated by Congress as a way for the
government to help keep the public informed about
substances or exposure circumstances that are “known” or
are “reasonably anticipated” to cause human cancers. The
report also identifies current regulations concerning these
listings in an attempt to address how exposures have been

The report makes a distinction between “known” human
carcinogens, where there is sufficient evidence from human
studies and “reasonably anticipated” human carcinogens,
where there is either limited evidence of carcinogenicity
from human studies and/or sufficient evidence of
carcinogenicity from experimental animal studies.

The report does not assess the magnitude of the
carcinogenic risk, nor does it address any potential
benefits of listed substances such as certain
pharmaceuticals. Listing in the report does not establish
that such substance presents a risk to persons in their
daily lives. Such formal risk assessments are the
responsibility of Federal, State, and local health
regulatory agencies.


STEROIDAL ESTROGENS. These are a group of related hormones
that control sex and growth characteristics and are
commonly used in estrogen replacement therapy to treat
symptoms of menopause and in oral contraceptives. The
report cites data from human epidemiology studies that show
an association between estrogen replacement therapy and a
consistent increase in the risk of endometrial cancer
(cancer of the endometrial lining of the uterus) and a less
consistent increase in the risk of breast cancer.

As for the other common use for steroidal estrogens, the
report says the evidence suggests estrogen-containing oral
contraceptives may be associated with an increased risk of
breast cancer but may protect against ovarian and
endometrial cancers.

produced by the sun as part of solar radiation and by
artificial sources such as sun lamps and tanning beds, in
medical diagnosis and treatment procedures, and in industry
for promoting polymerization reactions. The report cites
data indicating a cause-and-effect relationship between
this radiation and skin cancer, cancer of the lip and
melanoma of the eye. The report goes on to say that skin
cancers are observed with increasing duration of exposure
and for those who experience sunburn. The individual
components of UVR, which includes ultraviolet A,
ultraviolet B and ultraviolet C radiation, are listed in
the report, not as “known”, but as “reasonably anticipated”
human carcinogens — See below.

WOOD DUST. Listed as a “known human carcinogen” in this
report, wood dust is created when machines and tools cut,
shape and finish wood. Wood dust is particularly prevalent
in sawmills, furniture manufacture and cabinet making.
According to the report, unprotected workers have a higher
risk of cancers of the nasal cavities and sinuses.

NICKEL COMPOUNDS. Used in many industrial applications as
catalysts and in batteries, pigments and ceramics, the
report newly lists nickel compounds as “known” human
carcinogens based on studies of workers showing excess
deaths from lung and nasal cancers and on their mechanisms
of action.

One group of substances was upgraded from “reasonably
anticipated” to “known” human carcinogen:

are exposed via inhalation of beryllium dust or dermal
contact with products containing beryllium. Workers with
the highest potential for exposure include beryllium
miners, beryllium alloy makers and fabricators, ceramics
workers, missile technicians, nuclear reactor workers,
electric and electronic equipment workers, and jewelers.
According to data cited in the report, they have higher
risks for lung cancer which increase with their exposures
and which cannot be explained by tobacco smoking or other
occupational exposures.


IQ, or 2-amino-3-methylimidazo[4,5-f]quinoline, which is
formed during direct cooking with high heat of foods such
as meats and eggs and also found in cigarette smoke, is
listed as “reasonably anticipated to be a human carcinogen”
based on long-term animal studies. The report also states
there are several published human studies that suggest
there is an increased risk for breast and colorectal
cancers related to consumption of broiled or fried foods
that may contain IQ and/or other similar compounds formed
during cooking at high temperatures.

flame retardant chemical used to make some polyester resins
and rigid polyurethane foam is listed as “reasonably
anticipated” based on long-term animal feeding studies.

are listed as “reasonably anticipated to be human
carcinogens” because, according to the report, animal
studies show a cause-and-effect relationship between
exposure to each of these wavelength groups of broad
spectrum ultraviolet radiation (UVR) and skin cancer. The
report points out that the data on skin cancer in humans
for these different wavelengths of UVR are limited, because
it has been impossible to determine if the people in these
studies were exposed to “pure” individual components of UVR
or, as is more likely the case, to “mixtures” of the
different components thus making it impossible to say that
the observed skin cancers were due only to one of the
“pure” individual components.

CHLORAMPHENICOL. An antibiotic with restricted use in the
US because it can cause fatal blood disorders, is listed in
the report as “reasonably anticipated to be a human
carcinogen”. The report says the listing is based on
limited evidence from human studies that showed an
increased cancer risk for the occurrence of leukemia after
chloramphenicol therapy.

2,3-DIBROMO-1-PROPANOL, a chemical used as an intermediate
in the production of flame-retardants, insecticides, and
pharmaceuticals, is listed in the report as “reasonably
anticipated to be a human carcinogen” based on strong
evidence of cancer formation from skin painting study in
experimental animals.

have been used to color leather, paper, plastic, rubber and
textiles and are listed in the report because they are
metabolized to 3,3′-dimethoxybenzidine, which is
“reasonably anticipated to be a human carcinogen”.

have been used in printing textiles, in color photography
and as biological stains and are listed in the report
because these dyes are metabolized to 3,3′-
dimethylbenzidine, which is “reasonably anticipated to be a
human carcinogen”.

METHYLEUGENOL, occurs naturally in oils, herbs and spices
and is used in smaller amounts in its natural or synthetic
form in flavors, insect attractants, anesthetics and
sunscreens. It is listed in the report based on sufficient
evidence of cancer formation from oral studies of this
chemical in experimental animals.

METALLIC NICKEL, this metal is used mainly in alloys with
most exposures by inhalation or skin contact in the
workplace. (It should be noted that metallic nickel is not
contained in the nickel coin.) It is listed in the report
based on sufficient evidence of cancer formation from
studies of this chemical in experimental animals.

STYRENE7,8-OXIDE, is used in producing reinforced plastics
and as a chemical intermediate for cosmetics, surface
coatings, agricultural and biological chemicals. It is
listed in the report based on sufficient evidence of cancer
formation from studies of this chemical in experimental

VINYL BROMIDE, which has been used in polymers in making
fabrics for clothes and home furnishings, as well as in
leather and metal products, drugs and fumigants. It is
listed in the report based on sufficient evidence of cancer
formation from studies of this chemical in experimental

VINYL FLUORIDE, which is used in making polyvinyl fluoride
and related weather-resistant fluoropolymers. Support for
the listing came from inhalation studies in experimental
animals. It is listed in the report based on sufficient
evidence of cancer formation from studies of this chemical
in experimental animals.

The report is immediately accessible at

For available hard copies, email,
visit or write Environmental
Health Perspectives, Attn: Order Processing, 1001 Winstead
Drive, Suite 355, Cary, NC 27513. Requests for hard copies
may also be faxed to (919) 678-8696.

Fact sheets — “What is the “Report On Carcinogens”?” and “Q
and A on the RoC” as well as background documents for the
new listings — can be accessed at

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