[Federal Register Volume 76, Number 104 (Tuesday, May 31, 2011)]
[Notices]
[Pages 31329-31330]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-13395]
[[Page 31329]]
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ENVIRONMENTAL PROTECTION AGENCY
[EPA-HQ-OAR-2011-0436; FRL-9313-4]
EPA Radiogenic Cancer Risk Models and Projections for the U.S.
Population (Blue Book)
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice.
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SUMMARY: This document announces the availability of U.S. Environmental
Protection Agency's (EPA) updated EPA Radiogenic Cancer Risk Models and
Projections for the U.S. Population (EPA 402-R-11-001, April 2011),
also known as the Blue Book, which provides radiation risk assessment
methodology. EPA will use the scientific information on radiation risks
provided in the Blue Book, together with information from other
sources, when considering potential modifications and updates to
radiation protection rules and guidance.
FOR FURTHER INFORMATION CONTACT: David Pawel, Radiation Protection
Division (6608J), Environmental Protection Agency, 1200 Pennsylvania
Ave., NW., Washington DC 20460; telephone number: 202-343-9202; fax
number: 202-343-2302; e-mail address: [email protected].
SUPPLEMENTARY INFORMATION:
I. General Information
A. How can i get copies of this document and other related information?
1. Docket. EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2011-0436; FRL-9313-4]. Publicly available
docket materials are available either electronically through http://www.regulations.gov or in hard copy at the Air and Radiation Docket in
the EPA Docket Center, (EPA/DC) EPA West, Room 3334, 1301 Constitution
Ave., NW., Washington, DC. The EPA Docket Center Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Public Reading Room is
(202) 566-1744, and the telephone number for the Air and Radiation
Docket is (202) 566-1742. As provided in EPA's regulations at 40 CFR
Part 2, and in accordance with normal EPA docket procedures, if copies
of any docket materials are requested, a reasonable fee may be charged
for photocopying.
2. Electronic Access. You may access this Federal Register document
electronically through the EPA Internet under the ``Federal Register''
listings at http://www.epa.gov/fedrgstr/.
II. Background
The U.S. Environmental Protection Agency develops estimates of risk
from low-level ionizing radiation as part of its responsibilities for
regulating environmental exposures and in its role of providing Federal
Guidance on radiation protection.
The EPA Radiogenic Cancer Risk Models and Projections for the U.S.
Population, also known as the Blue Book, is a revision to EPA's
methodology for estimating radiogenic cancer risks. These updates are
based on the National Research Council's latest report on Biological
Effects of Ionizing Radiation (BEIR VII) as well as other updated
science.
The Blue Book uses the best science available to calculate cancer
risk estimates separately by age at exposure, sex, and potentially
affected organ. More specifically, the Blue Book presents new EPA
estimates of cancer incidence and mortality risk coefficients
pertaining to low dose exposures to ionizing radiation for the U.S.
population, as well as their scientific basis. (Risk here refers to the
probability of a health effect, i.e., a cancer or a cancer death; a
risk coefficient refers to the risk per unit dose of ionizing
radiation.)
The Blue Book has undergone an extensive peer review process. It
takes into account recommendations made by the Agency's Science
Advisory Board (SAB), which completed its review in January 2010. For
the Blue Book review, the SAB relied on advice from its Radiation
Advisory Committee--a panel of non-EPA scientists, who are chosen for
their objectivity, integrity, and expertise in radiation science and
protection.
As in BEIR VII, models in the Blue Book are provided which describe
how radiogenic cancer risks depend on such factors as: (1) When a
person is exposed, (2) at what age a person might get cancer, (3) sex,
(4) and the type of cancer. Estimates of cancer risk are based on these
models. However, a number of extensions and modifications to the BEIR
VII models have been implemented. Most notably, the Blue Book provides:
(1) Risk estimates for [alpha]-particles which were not addressed in
BEIR VII; (2) risk estimates for some types of cancer that were not
considered in BEIR VII: basal cell carcinomas, kidney cancer, bone
sarcomas, and also cancers from prenatal exposures, and (3) a more
thorough analysis of uncertainties associated with the radiogenic risk
estimates.
Underlying the risk models is a large body of epidemiological and
radiobiological data. In general, results from both lines of research
are consistent with a linear, no-threshold dose (LNT) response model in
which the risk of inducing a cancer in an irradiated tissue by low
doses of radiation is proportional to the dose to that tissue. The BEIR
VII Committee unequivocally recommended continuing adherence to the LNT
approach. EPA also finds strong scientific support for LNT, while
acknowledging that new research might conceivably lead to revisions in
the future.
The most important source of data on radiogenic health effects is a
long-term epidemiological study of Japanese atomic bomb survivors, who
received an essentially instantaneously delivered dose of radiation,
mostly in the form of [gamma]-rays. This study has important strengths,
including: An exposure which can be pinpointed in time; a large,
relatively healthy exposed population encompassing both genders and all
ages; a wide range of radiation doses to all organs of the body, which
can be estimated reasonably accurately; and detailed epidemiological
follow-up for about 50 years. The precision of the derived risk
estimates is higher than all other studies for most cancer types.
Nevertheless uncertainties in the risk estimates are often quite large
for specific cancers, and the uncertainties are even larger if one
focuses on a specific gender, age at exposure, or time after exposure.
Calculating radiogenic risks is further complicated because radiogenic
risks may be different for the U.S. population than for the Japanese A-
bomb survivors. Such differences may be due to genetic or environmental
factors, e.g., radiogenic lung cancer risks likely depend on patterns
of tobacco use.
In addition to the Japanese Life Span Study (LSS), other
epidemiological studies provide important information about radiogenic
cancer risks. These include studies of medically irradiated patients
and groups receiving occupational or environmental exposures. For
thyroid and breast cancers, risk estimates are based on data from both
the A-bomb survivors and medically irradiated cohorts. While studies on
populations exposed occupationally or environmentally have, so far,
been of limited use in quantifying radiation risks, they can provide
valuable insight into the risks from chronic exposures.
Summary risk coefficients are provided for the U.S. population,
which can be used to calculate average risks for persons exposed
throughout life to a
[[Page 31330]]
constant dose rate. The average lifetime dose from natural background
radiation (not including radon) is about 75 mGy. Using the summary risk
coefficients in the Blue Book, this corresponds to about 87 out of
10,000 people in the U.S. who would get cancer from natural background
radiation, with 44 out of the 87 resulting in death. Radiogenic risks
(per unit dose) are substantially larger for childhood than adult
exposures, and tend to be larger for females than males. Risks per unit
dose are larger for breast, lung and colon cancers than for most other
cancer sites.
For both males and females, the estimated risk for cancer incidence
(for all cancers combined) increased by about 35% from EPA's previous
estimates published in Federal Guidance Report 13 (FGR-13). However,
for some individual cancer sites, relative changes in cancer incidence
are more than two-fold. In general, the new EPA mortality estimates do
not differ greatly from those in FGR-13; remarkably, for all sites
combined, the estimates for mortality changed by less than 2% for both
males and females.
Aside from the case of radon (which is not in the scope of this
report), human data on risks from [alpha]-particles are much more
limited than for most other types of radiation. For most cancer types,
results from laboratory experiments indicate that the risk per unit
dose may be about 20 times greater for [alpha]-particles than for
[gamma]-rays. Thus, risk coefficients for [alpha]-particles (for most
cancers) are derived by multiplying the corresponding risk coefficients
for [gamma]-rays by a factor of 20.
EPA will use the scientific information on radiation risks provided
in the Blue Book, together with information from other sources, when
considering potential modifications and updates to radiation protection
rules and guidance. The complete Blue Book, EPA Radiogenic Cancer Risk
Models and Projections for the U.S. Population (EPA 402-R-11-001, April
2011), can be accessed at http://epa.gov/radiation/assessment/blue-book/index.html.
Dated: May 24, 2011.
Michael P. Flynn,
Director, Office of Radiation and Indoor Air.
[FR Doc. 2011-13395 Filed 5-27-11; 8:45 am]
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