Document ID: EPA-HQ-OAR-2005-0083-0381
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-12-01T05:00Z

The Radiation Public Health Project (RPHP) asserts that levels of
radioactive strontium-90 are rising in the environment and that these
increased levels are responsible for increases in cancers, specifically
cancers in children, and infant mortality.  They state that effluents
from nuclear power plants are directly responsible for the increases in
strontium-90.  However, numerous, peer-reviewed, scientific studies do
not substantiate such claims.

What is Strontium-90?

Strontium-90 (Sr-90) is a byproduct of the fission process.  It does not
occur naturally.  It is radioactive and has a 29.1 year half-life.  It
decays primarily by the emission of a beta particle. The primary pathway
for Strontium-90 to enter the body is through ingestion of contaminated
foods and milk.  

Why is Strontium-90 in the environment?

There are three sources of strontium-90 in the environment:  fallout
from nuclear weapons testing, releases from the Chernobyl accident in
the Ukraine and releases from nuclear power reactors.  By far the
largest source of strontium-90 is from weapons testing fallout.

Strontium-90 was released to the atmosphere by above-ground explosions
of nuclear weapons [UNSCEAR 2001]).  Although the United States
performed its last atmospheric test of a nuclear weapon in 1963, other
countries continued to perform atmospheric testing of nuclear weapons
until 1980 (UNSCEAR 2001).  Approximately 622 PBq (16.8 million Ci) of
strontium-90 were produced and globally dispersed in atmospheric nuclear
weapons testing. (UNSCEAR 2001) With a 29.1 year half life, significant
levels of strontium-90 still remain in the environment.

μSv (9.7 mrem).  The worldwide average effective dose from inhaling
strontium-90 (1945 to 1985) is 9.2 μSv (0.92 mrem).  These doses are
well below those doses know to cause health effects. (NCRP 1991).

The other two sources of strontium-90 in the environment are from the
Chernobyl accident in April 1986 when approximately 8 PBq (216,0000 Ci
of strontium-90 were released into the atmosphere, and strontium-90
released from nuclear power reactor operations.  The total annual
release of strontium-90 into the atmosphere from all U.S. nuclear power
plants (103 nuclear power plants) varies from year to year, but could
range from low, i.e., 4.5MBq (0.00012 Ci) to as much as 55 MBq
(approximately 0.001 Ci of strontium-90) (NUREG/CR-2907 Vol.12).  At an
individual nuclear power plant, these levels are so low that they are
usually at or below the minimum detectable activity of the sensitive
detection equipment. 

Does the federal government monitor strontium-90 in the environment?

All nuclear power plants must file annual effluent reports with the NRC.
 These reports list the isotopes released, the quantity released and the
resultant dose to a member of the public. These reports are available to
the public. In addition, the Environmental Protection Agency routinely
monitors radioactivity in the environment, including  strontium-90
levels in milk.  The EPA (ERAMS) Pasteurized Milk Program consists of 43
sampling locations that represent a significant portion of the milk
consumed in major population centers. Milk is sampled because it is a
readily available food source consumed by a large portion of the
population; because it is consumed by children in relatively large
quantities, which provides a good indication of children's exposure to
nuclear events; and, finally, because it is a good indicator of
radionuclides present in the environment.  The primary functions of this
monitoring program are to obtain reliable monitoring data about current
radionuclide concentrations and to monitor long-term trends.  The
quarterly samples are analyzed to look for fission products such as
iodine-131, cesium-137, barium-140 which could become present in the
event of a nuclear accident.  Levels of strontium-90 are also analysed
but on a less frequent schedule.  The results of the radionuclide
sampling are posted on the EPA website,

http://www.epa.gov/narel/erams/erdonline.html.

Effluent Monitoring at nuclear power plants

As stated above, all nuclear power plants must file annual effluent
reports with the NRC which detail the quantity of the radioactivity
released, identifies the radionuclides that are released and the
resultant radiation dose to the public.  The requirements of the
effluent report are contained in NRC Regulatory Guide 1.21, (Measuring,
Evaluating, and Reporting Radioactivity in Solid Wastes and Releases of
Radioactive Materials in Liquid and Gaseous Effluents from
Light-Water-Cooled Nuclear Power Plants (Rev. 1).(

Regulatory Guide 1.21 recommends that (a quarterly analysis for
strontium-89 and strontium-90 should be made on a composite of all
filters from each sampling location collected during the quarter.(  The
sensitivity is such that the analysis for radioactive material in
particulate form should be sufficient to permit measurement of a small
fraction of the activity, which would result in annual exposures of 0.15
mSv (15 mrem) to any organ of an individual, or 0.05 mSv (5 mrem) to
the whole body, in an unrestricted area.  Nuclear power plants are
allowed to release radioactive effluents up to specified regulatory
limits as defined in Appendix B to Part 20 of the Code of Federal
Regulations (CFR).  Appendix B lists the concentrations of effluents of
all radionuclides that may be released to the environment.  These
concentration values are equivalent to the radionuclide concentrations
which,if inhaled or ingested continuously over the course of a year,
would produce a total effective dose equivalent of 50 millirem (0.5
millisieverts).  However, nuclear power reactor effluents are limited by
license conditions which require compliance with Appendix I to 10 CFR
Part 50.  Appendix I contains the criteria for maintaining radioactive
material effluents from nuclear power reactors, as low as reasonably
achievable. The dose criterion for releases of effluents to unrestricted
areas is 5 millirem to the total body or 15 millirem to any organ.

To demonstrate that the plant is within the regulatory limits, the
plant operators rigorously sample and analyze the waste stream. 
Radiological samples around the plant site are also analyzed.  Both
strontium-89 and strontium-90 may be found in power plant effluents in
small quantities.  Strontium-89 has a half-life of 50 days.  Due to its
short half-life, any strontium-89 from atmospheric weapons testing has
decayed away.

If strontium-90 levels are rising due to nuclear power plant effluents,
as suggested by Radiation Public Health Project then these increased
levels would be seen in environmental samples in the areas surrounding,
as well as downwind from the plant site.  Environmental samples, such as
soil, vegetation, water, could be obtained and analyzed.  Such sampling
and analyses would indicate if strontium levels are, in fact, rising. 
It could also characterize the quantities released as well as deposition
patterns.  It is reasonable to conclude that strontium would be seen in
the environment well before it is seen in baby teeth.  In order for it
to be in the environment from nuclear power plants, it would have to be
seen in significant quantities in the waste stream of these facilities. 
It is not.

Use of (In-Body( Radionuclide Measurements to Assess Public Risk from
Radiological Effluents from Nuclear Power Plants.

The authors of the many Radiation Public Health Project reports have
stated or  implied that the federal government/NRC should measure
radioactive substances in persons living near nuclear power plants. 
Such measurements would be misleading and unwarranted for a variety of
reasons:

  $	Interpreting measurements of radioactive materials in people is
difficult unless one knows what each individual was exposed to, when the
exposures occurred, and by what routes they occurred (ingestion,
inhalation, etc.).  In particular for strontium-90, dietary
contributions from foodstuffs produced out of the region must be
considered.  Finally, migration must be accounted for, because people
may have lived and acquired radionuclides elsewhere than near a nuclear
power plant.

  (	Substances in the human body are dynamic, not static.  This includes
radioactive and nonradioactive substances.  The dynamic processes
include intake of material; uptake to systemic circulation from the
gastrointestinal tract, respiratory tract, or skin; translocation
throughout the body system; retention over time; and elimination via
excretion and radioactive decay.  Thus, even in deciduous teeth, the
time course of exposure leading to intake and all other dynamic
processes must be considered to interpret measurements.

 $	Radioactive substances may come from a variety of sources.  In the
case of strontium-90, the primary source has always been fallout from
atmospheric weapons tests (UNSCEAR 2001). 

  $	If strontium-90 is not found in environmental samples around nuclear
power plants nor in any detectable quantity in the effluent stream of
nuclear power plants, performing in-body analyses for strontium-90 just
doesn(t make sense.



Ability for Strontium-90 to Cause Cancer

Strontium-90 is not harmful unless it is near or inside the body.  It is
easily shielded if outside the body, resulting in no radiation exposure.

If ingested, strontium-90 tends to mimic calcium when it is in the body
and therefore becomes concentrated in calcified tissues such as bones
and teeth.  If ingested in quantities that produce very large
radiological dose rates (about thousand times higher than dose rates we
all receive from natural background), strontium-90 is known to increase
the risk of bone cancer and leukemia in animals, and is presumed to do
so in people.  Below these doses, there is no evidence of excess cancer 
[Raabe 1994].

Cause-and-Effect Relationship Between Radiological Releases from Nuclear
Power Plants and Alleged Increased Incidence in Cancers in the
Surrounding Communities

The authors of the Radiation Public Health Project reports have stated
or implied that claimed statistical associations between cancer rates
and reactor operations are cause-and-effect relationships.  Many
excellent scientific minds have addressed the question of when one can
decide that an association is causal, that is, when two things that
appear to be associated over time can lead one to deduce that one causes
the other.

A simple counterexample helps illustrate this point.  A college
professor gives the following example of a causal inference:  (In the
winter I wear galoshes.  In the winter I get colds.  Therefore, galoshes
cause colds.(  There(s no argument that a strong statistical association
exists between wearing galoshes and the health effect of colds.  There
is, however, an argument about whether galoshes cause colds.  So, how
does one go about addressing whether this association is really
causation?

Here are some of the major factors to consider before inferring that a
statistical association is a causal one (Hill 1965):

(1)	Strength:  Is a large effect observed, e.g., 32-fold lung cancer
increase in heavy smokers?

(2)	Consistency:  Is the effect consistently observed across studies?

(3)	Specificity:  Does the effect occur in specific persons, for
particular sites and types of disease.

(4)	Temporality:  Does exposure precede disease? Is there a suitable
latent period between exposure and clinical symptoms?

(5)	Biological Gradient:  Is there a dose-response curve in which
increasing dose leads to increasing response?

(6)	Biological Plausibility:  Is there a plausible biological mechanism
for the observed association?

(7)	Coherence:  Does the cause-and-effect inference seriously conflict
with generally known facts of the natural history and biology of the
disease?

(8)	Experiment:  Does intervention reduce or prevent the association?

(9)	Analogy:  Do other, similar agents produce the effects?

Statistical association alone does not prove causation.  The Radiation
Public Health Project work fails to meet many of these criteria, even if
the strontium-90 measurements were the result of the nuclear power plant
operations.  In particular, they fail to meet criteria 1, 2, 3, 4, and
6.

Epidemiology is the study of patterns of health and disease in human
populations.  In 1995 an international group of experts assembled to
help determine how to use epidemiology studies for risk assessments. 
Their work has been published (Federal Focus Inc. 1996) and a
non-copyrighted summary can be found on the internet at
http://www.pnl.gov/berc/epub/risk/index.html.

A disease cluster is a group of cases of a disease that appear around
the same time in a limited geographic or occupational area.  A very
readable, non-technical analysis of (the cancer-cluster myth( has been
published in a popular magazine (Gawande 1999).  Gawande explains why
infectious disease clusters can and should spur immediate investigations
and perhaps intervention by public health officials, and yet why
non-infectious disease clusters rarely, if ever, are verified (see, for
example, Neutra 1990 and Reynolds et al. 1996).  For cancer, which has a
significant latency between exposure and appearance of clinical
symptoms, apparent clusters are very misleading because of migration and
confounding sources of exposure.

Are there Increases in Cancer Rates Around Nuclear Power Plants?

While the authors of the Radiation Public Health Project reports are
correct with regard to the general increase in cancer incidence in the
United States, this increase does not appear to be due to environmental
causes other than cigarette smoking.   The National Cancer Institute
(NCI 2001) states that

(It is true that a person(s chance of developing cancer within his or
her lifetime is almost twice as great today as it was half a century
ago, which means that doctors are seeing more cases of cancer than they
did in the past.  However, this increase is caused largely by the facts
that people are living longer and cancer is more prevalent in older
people.  When corrected for the increasing average age of the
population, cancer rates in the United States have actually been stable
or even falling slightly in the past several years.  Much of the rise
prior to that was due to cigarette smoking, a well established and
avoidable cause of cancer.(

For example, there was a dramatic increase in prostate cancer between
1989 and 1992.  The American Cancer Society (ACS 2001b) acknowledges
that there was an increase in reported prostate cancers, but they state
that this increase was apparent rather than real.  They suggest that it
was due to earlier diagnosis in men without any symptoms by increased
use of prostate-specific antigen (PSA) blood test screening.  They note
that prostate cancer incidence rates have declined significantly since
1992 (ACS 2001b).

At the request of Congress, the NCI conducted a study of cancer
mortality rates around 52 nuclear power plants, nine DOE facilities,
and one former commercial fuel reprocessing facility.  The study covered
the period from 1950 to 1984, and evaluated the change in mortality
rates before and during facility operations.  The study (Jablon, Hrubec,
and Boice 1991) concluded the following:

(From the evidence available, this study has found no suggestion that
nuclear facilities may be linked causally with excess deaths from
leukemia or from other cancers in populations living nearby.(

Additionally, the American Cancer Society (ACS 2001c) has concluded that
although reports about cancer case clusters in such communities have
raised public concern, studies show that clusters do not occur more
often near nuclear plants than they do by chance elsewhere in the
population.  Likewise, there is no new evidence that links strontium-90
with increases in breast cancer, prostate cancer, or childhood cancer
rates.  The American Cancer Society recognizes that public concern about
environmental cancer risks often focuses on risks for which no
carcinogenicity has been proven or on situations where known carcinogen
exposures are at such low levels that risks are negligible.  (Ionizing
radiation emissions from nuclear facilities are closely controlled and
involve negligible levels of exposure for communities near such plants (
(ACS 2001c).

Some states have examined the state specific cancer data presented by
the Radiation Public Health Project in various reports over the years. 
In Florida, due to the statements made by the Radiation Public Health
Project suggesting that cancer rates in communities surrounding nuclear
power plants are elevated when compared to the rest of the state, the
Department of Health chose to look at the cancer rates using the same
data used by Radiation Public Health Project.  Staff from the Florida
Bureau of Environmental Epidemiology interviewed the Radiation Public
Health Project staff to determine the source of data and then performed
their own calculations.  The conclusion of this analysis by the
officials in Florida stated:

In summary, we reconstructed the calculations made by the Radiation
Public Health Project using the same data from which they base their
claims.  Radiation Public Health Project claims that there are striking
increases in cancer rates in southeastern Florida counties and
attributes these increases to radiation exposures from nuclear reactors.
 Using this data to reconstruct calculations and graphing our findings,
we have not been able to identify unusually high rates of cancers in
these counties.  As we would expect, just by chance, some county rates
appear higher that state and national trends and some appear lower. 
These rates fluctuate from year to year and in some situations, large
fluctuations occur with a small number of cases and small underlying
county populations.  Ones has to use careful scientific and objective
evaluations of these fluctuations to avoid misinterpretation.  Careful
analysis and observation of the data presented here dose not support the
alarming claims made by the Radiation Public Health Project regarding
cancer mortality rates and trends in southeastern Florida counties when
compared with the rest of the state of Florida and the nation.  (FDOH
2001)

Infant Mortality  and Nuclear Power Plant Effluents

The authors of the Radiation Public Health Project reports allege
increases in infant mortality.   The authors examine only the number of
infant deaths and rates and do not examine or even acknowledge the
contribution of the known risk factors for infant mortality.  These risk
factors include (1) conception at a young age; (2) poor health and/or
nutritional status of the mother; (3) socio-economic status of the
mother; (4) education of the mother; (5) domestic violence; (6) some
infections (e.g., reproductive tract infections and peridontal
infections); (7) substance abuse (e.g., tobacco, alcohol and other
drugs((both illegal and prescriptive); (8) closely-spaced pregnancies;
(9) inadequate prenatal care; (10) inadequate folic acid intake; and
(11) positioning babies on their stomachs to sleep. (GADOH)

Additionally, the authors have not examined infant mortality rates prior
to reactor operations, nor have they studied control populations. 
Without systematic examination of the contribution of each of these risk
factors, no meaningful conclusions can be reached regarding any impact
of nuclear power plant effluents on infant mortality.

Regulatory Basis and Discussion of Risk

The evaluation of health effects from exposure to radiation, both
natural and man-made, is an ongoing activity involving public, private,
and international institutions.  International and national
organizations such as the International Commission on Radiological
Protection (ICRP) and the National Council on Radiation Protection and
Measurements (NCRP) provide consensus standards developed from recent
and ongoing research.  NRC(s regulatory limits for effluent releases and
subsequent dose to the public are based on the radiation protection
recommendations of these organizations.  NRC provides oversight of all
licensed commercial nuclear reactors to ensure that regulatory limits
for radiological effluent releases and the resulting dose to the public
from these releases are within the established limits.  The regulations
related to radiological effluents and dose to the public can be found in
10 CFR Part 20 and 10 CFR Part 50, Appendix I.

The National Academy of Sciences( Committee on the Biological Effects of
Ionizing Radiation (BEIR) published its fifth report (BEIR V) just over
a decade ago (National Research Council 1990).  That report contains
mathematical models that predict risk of radiation-induced cancers in
human populations over and above the incidence of cancer that occurs in
the absence of radiation exposure.  The BEIR V committee chose a linear,
nonthreshold (LNT) dose-response model for solid cancers and a
linear-quadratic (LQ) model for leukemia.

The BEIR V report does not address what is safe or not safe; it merely
evaluates excess cancer risk in terms of probabilities.  ICRP
Publication 60 (1991), however, does define safe in the sense of
(acceptable risk,( and this and similar definitions have been reaffirmed
by the NCRP (NCRP 1993) and the U.S. Environmental Protection Agency
(EPA 1987).  These implicit definitions of (safe( are embodied in all
U.S. radiation protection regulations, including those of the NRC.

There is no human activity without some risk, however slight, so (safe(
does not mean (with no risk,( but rather (safe( means (with an
acceptably tiny risk.(  What risk is acceptable from society(s
standpoint is determined by the political process in the United States
as spelled out recently, for example, by the U.S.
Presidential/Congressional Commission on Risk Assessment and Risk
Management  (Omenn et al. 1997).

General Comments on the Scientific Methodology used by Radiation Public
Health Project

There are principles of good science as recognized by the scientific
community:

1. Can and has this study been replicated?  Good science can always be
repeated.

2. Does this study have a bias, such as being selective in the
population, or in the years studied?

3. Was the study subject to peer review?  During peer review, other
experts check the fundamental hypothesis and methodology.  Radiation
Public Health Project publishes in limited journals.  A review of the
circulation of these journals suggests that they are not widely
distributed, i.e. 280 subscribers, vs the thousand of subscribers of
epidemiological journals.  Has Radiation Public Health Project had their
studies reviewed and published in mainstream journals?

The authors of the various Radiation Public Health Project reports,
including the most recent report (  An unexpected rise in strontium-90
in US deciduous teeth in the 1990s( , the Science of the Total
Environment, (1) have not established control populations for study; (2)
have not examined the impacts of other risk factors;(3) have used very
small sample sizes to draw general conclusions, (for example, thirteen
teeth from Philippine residents were used to compare against the 2089
teeth analyzed in the US); (4) have not performed environmental sampling
and analysis; (5) have repeatedly and incorrectly stated that certain
EPA analyses have been discontinued, when in fact they have not been;
(6) have selectively chosen to ignore data, (infant mortality rates in
certain counties or during certain periods of time were not considered
because they did not (fit(; (7) have not subjected their data to the
independent review of the mainstream scientific community; (8) have used
an incorrect half-life for strontium-90 to give the false impression
that strontium levels in the environment were decaying more rapidly than
in baby teeth.  In general, the authors have not followed good
scientific principles. 

Suugested References for Further Study

American Cancer Society (ACS).  2001b.  (Prostate Cancer.( 

American Cancer Society (ACS).  2001c.  (1998 Facts & Figures. 
Environmental Cancer Risks.(  Accessed online: 
http://www.cancer.org/statistics/cff98/enviromental.html.

Eisenbud, M.  1987.  Environmental Radioactivity, 3rd Edition.  Academic
Press, San Diego, California.

Federal Focus Inc.  1996.  Principles for Evaluating Epidemiologic Data
in Regulatory Risk Assessment.  Developed by an Expert Panel at a
Conference in Long, England, October 1995.  Available at
http://www.pnl.gov/berc/epub/risk/index.html.  Federal Focus, Inc.,
Washington, D.C.

Florida Department of Health (FDOH).  2001.  Report Concerning Cancer
Rate in Southeastern Florida.  Bureau of Environmental Epidemiology,
Division of Environmental Health, Tallahassee, Florida.

Gawande, A.  1999.  "The Cancer-Cluster Myth." The New Yorker
LXXIV(45):34-37.

Georgia Department of Human Resources (GADOH), Division of Public
Health, Epidemiology and Prevention Branch, Perinatal Epidemiology Unit,
1997. The Challenge of Change: A Mid-Decade Look at Maternal and Child
Health in Georgia, Publication Number: DPH97.53HW

Gould, J. M., E. J. Sternglass, J. D. Sherman, J. Brown, W. McDonnell,
and J. J. Mangano.  2000.  (Strontium-90 in deciduous teeth as a factor
in early childhood cancer.(  International Journal of Health Services. 
Vol. 30, No. 3.

Hill A. B.  1965.  "The Environment and Disease: Association or
Causation?"  Proceedings of the Royal Society of Medicine 58:295-300.

International Commission on Radiological Protection (ICRP).  1991. 
"1990 Recommendations of the International Commission on Radiological
Protection.(  (ICRP Publication No. 60) Annals of the ICRP 21(1-3),
Pergamon Press, New York.

Jablon, S., Z. Hrubec, and J. D. Boice, Jr.  1991.  (Cancer in
populations living near nuclear facilities, A survey of mortality
nationwide and incidence in two states.(  Journal of the American
Medical Association.  265:1403-1408.

Mangano, J. et al, 2003 (An unexpected rise in strontium-90 in US
deciduous teeth in the 1990s.(  the Science of the Total Environment, 
Elsevier Press

National Cancer Institute (NCI).  1990.  Cancer in Populations Living
Near Nuclear Facilities.  Bethesda, Maryland.

National Cancer Institute (NCI).  2001.  (Is there a cancer (epidemic?(
 Accessed online:  
http://rex.nci.nig.gov/behindthenews/uc/ucframe.html. 

National Council on Radiation Protection and Measurements (NCRP).  1991.
 Some Aspects of Strontium Radiobiology.  Report No. 110, NCRP
Publications, Bethesda, Maryland.

National Council on Radiation Protection and Measurements (NCRP).  1993.
 Limitation of Exposure to Ionizing Radiation. Report No. 116, NCRP
Publications, Bethesda, Maryland.

National Research Council.  1990.  Health Effects of Exposure to Low
Levels of Ionizing Radiation (BEIR V).  National Academy Press,
Washington, D.C.

Neutra, R. R.  1990.  "Counterpoint from a cluster buster."  Am. J.
Epidemiol. 132(1):1-8.

Norman, G. and D. Streiner, 2000.   Biostatistics.  BC Decker, Inc.
Hamilton, Ontario, Canada

Omenn, G. S., A. C. Kessler, N. T. Anderson, P. Y. Chiu, J. Doull, B.
Goldstein, J. Lederberg, S. McGuire, D. Rall, and VV. Weldon.  1997. 
Framework for Environmental Health Risk Management.  Final Report.  Vol.
1.  U.S. Government Printing Office, Washington, D.C.

Page, R., G. Cole, and T. Timmreck 1995 Basic Epidemiological Methods
and Biostatistics(

Jones and Bartlestt Publishers, Sudbury, MA

Raabe, O. G.  1994.  "Three-Dimensional Models of Risk From Internally
Deposited Radionuclides."  Chapter 30 in Internal Radiation Dosimetry,
ed. O. G. Raabe, pp. 633-658. Medical Physics Publishing, Madison,
Wisconsin.

Reynolds, P., D. F. Smith, E. Satariano, D. O. Nelson, L. R. Goldman,
and R. R. Neutra.  1996.  "The four county study of childhood cancer:
clusters in context."  Statistics in Medicine 15(7-9):683-697.

Sturgeon, S. R., C. Schairer, M. Gail, M. McAdams, L. A. Brinton, and R.
N. Hoover.  1995.  (Geographic Variation in Mortality from Breast Cancer
Among White Women in the United States.(  Journal of the National Cancer
Institute.  87:1846-1853.

United Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR).  2000.  Sources and Effects of Ionizing Radiation, Vol. 1: 
Sources.  United Nations, New York.

United Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR).  2001.  Sources and Effects of Ionizing Radiation:  UNSCEAR
2000 Report to the General Assembly, with Scientific Annexes.  Vol. I: 
Sources.  United Nations, New York.

U.S. Environmental Protection Agency (EPA).  1987.  "Radiation
Protection Guidance to Federal Agencies for Occupational Exposure." 
Federal Register 52(17):2822-2834.

U.S. Nuclear Regulatory Commission (NRC) 1991. NUREG/CR-2907, Vol.12
(Radioactive Materials Released from Nuclear Power Plants, Annual
Report(

RADIATION PUBLIC HEALTH PROJECT

FACT SHEET

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