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United States
Environmental
Protection Agency
Office of Water
Mail Code 4607M
June 2016
Draft Protective Action
Guide (PAG) for
Drinking Water

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Draft Protective Action Guide (PAG)
for Drinking Water
Prepared by:
U.S. Environmental Protection Agency
Office of Water
Office of Ground Water and Drinking Water
Washington, DC 20460
Date: June 2016
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Draft Protective Action Guide (PAG) for Drinking Water
1.0 INTRODUCTION
This proposal presents the protective action guide (PAG) and planning guidance to help
protect the public in the event of a radiological incident that affects drinking water
sources. A PAG is the projected dose to an individual from a release of radioactive
material at which a specific protective action to reduce or avoid that dose is
recommended.
The protective action for the drinking water exposure pathway is to restrict the use of
contaminated water for drinking purposes and to provide alternative drinking water for
the affected community. The drinking water PAGs apply during the intermediate phase
of an incident, which may last for weeks to months1. This guidance only provides
recommendations and does not confer any legal rights or impose any legally binding
requirements upon any member of the public, states, or any other federal agency2.
2.0 THE DRINKING WATER PAG
Currently there is no intermediate PAG for drinking water. Drinking water is an essential
necessity for all people. The EPA determined, given the drinking water contamination
that occurred in Japan following the Fukushima event, that a drinking water PAG is
necessary. This proposal intends to provide the necessary tools to inform the level at
which local emergency responders should restrict consumption of drinking water
contaminated during a radiological emergency. In addition, based on public comment
received in response to the revised interim PAG manual (2013), EPA believes that this
proposal will make the overall PAG document a more robust and complete tool to be
used by emergency responders.
EPA is proposing a two-tier drinking water PAG that would be used during the
intermediate phase following a radiation incident: 500 millirem ((mrem) (5 millisievert
1	The intermediate phase is defined as the period beginning after the source and releases have been brought
under control (has not necessarily stopped but is no longer growing) and reliable environmental measurements are
available for use as a basis for decisions on protective actions and extending until these protective actions are no
longer needed. The intermediate phase includes protective action recommendations for relocation of the public,
worker exposure, reentry, food interdiction, and water interdiction. This phase may last from weeks to months and
could also overlap the early phase (hours to days) and late phase (months to years).
2	This guidance does not address or impact actions occurring under other statutory authorities such as the
United States Environmental Protection Agency's (EPA) Superfund program, the Nuclear Regulatory Commission's
(NRC) decommissioning program, or other federal or state programs. As indicated by the use of non-mandatory
language such as "may," "should" and "can," this guidance only provides recommendations and does not confer any
legal rights or impose any legally binding requirements upon any member of the public, states, or any other federal
agency.
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(mSv)) projected dose3 for the general population (defined as anyone over age 15,
excluding pregnant women and nursing women), and 100 mrem (1 mSv) projected dose
for pregnant women, nursing women and children age 15 and under4.
EPA expects that the responsible party for any drinking water system adversely
impacted during a radiation incident will take action to return to compliance with Safe
Drinking Water Act (SDWA) maximum contaminant levels as soon as practicable. The
proposed drinking water PAG provides a level of protection for the general population
consistent with PAGs currently in place for other media in the intermediate phase (i.e.,
the Food and Drug Administration's 500 mrem PAG for ingestion of food5 6) and
provides an additional level of protection for the most sensitive life stages. Intermediate
phase doses can be projected using a one-year duration and compared to the PAG so
that actions can be taken to avoid the exposure.
The already promulgated FDA food PAG and this proposed EPA drinking water PAG
are designed to complement each other, and allow emergency response officials to
account for and address doses from both eating contaminated food and drinking
contaminated water. The food ingestion and drinking water pathways are inherently
related because both address exposure through ingestion. In addition, water may be
used in the preparation of some food products, and radionuclides in water may affect
crops and ultimately enter the food supply. The FDA food PAG accounts for water
intrinsic in food as purchased and EPA's proposed PAG accounts for drinking water,
including water added to foods during preparation7.
PAGs for both food and drinking water are needed because a radiological incident may
affect the food supply and drinking water differently. In addition, because drinking water
is usually locally controlled and food is frequently shipped in from distant locations,
different and separate interdiction approaches would be appropriate. Finally, as
explained in the revised interim PAG manual (2013)8, the various PAGs are designed to
work in concert, allowing emergency responders to choose the exposure reduction
strategies that match the exposure scenario, community needs, and resources available
in the particular emergency.
3	All dose values expressed as Committed Effective Dose (CED) projected over one year. The CED, as
defined in FGR-13 (1999) and ICRP 103 (2007), is the sum of the product of all organ doses times their tissue
weighting factors.
4	Emergency management officials may consider whether it is appropriate to extend the lower tier to
individuals beyond age 15 or to women who are trying to get pregnant or who believe they might be pregnant.
5	Food and Drug Administration (FDA). 1998. Accidental Radioactive Contamination of Human Food and
Animal Feeds: Recommendations to State and Local Agencies. Available online at:
http://www.fda. gov/downloads/MedicatDeviees/.../UCM094513.pdf.
6	FDA. 2004. Supporting Document for Guidance Levels for Radionuclides in Domestic and Imported
Foods. Docket No. 2003D-0558.
7	Liquid beverages as well as milk are covered under the FDA food PAG.
8	EPA. 2013. Draft PAG Manual for Interim Use and Public Comment. Available online at:
http://www2.epa.gov/sites/production/files/2014-ll/documents/pag-manual-interim-public-comment-4-2-2013.pdf.
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While FDA and EPA would work closely together in a radiological response, the two
agency's authorities are separate so different strategies may be needed to protect
drinking water and the food supply.
A PAG is intended as a point of reference to aid emergency response managers in their
decision-making. After a particular situation stabilizes and becomes more clearly
defined, local authorities may wish to modify the PAG level they consider to be
appropriate in order to implement longer-term dose reduction strategies. EPA expects
that the responsible party for any drinking water system adversely impacted during a
radiation incident will take action to return to compliance with maximum contaminant
levels (MCLs) as soon as practicable.
Should a major radiological event occur, emergency response officials should consider
potential doses from all affected pathways (e.g., airborne plume, ground contamination,
drinking water, foods) when making protective action decisions. Consideration of the
specific conditions facing a community should be used in determining how each PAG
should be implemented. Protective actions might include restrictions on consumption of
garden produce, locally produced foods or embargo on sales of certain products, as
well as drinking water actions described in Section 6.0 of this proposal. Local decision
makers will need to determine the appropriate PAGs depending on projected risk. For
the PAGs, exposure routes are divided up by time and circumstance to allow the many
different potential protective actions to be tailored to the specific risks that must be
addressed. The full PAG Manual addresses all of the other pathways (plume inhalation,
immersion, ground shine, skin and thyroid doses in particular, long term exposure to
contamination, reentry and return to complete cleanup work, etc.) but always within
parameters appropriate to a corresponding PAG.
Section 7.0 explains how to calculate Derived Response Levels (DRLs) for
radionuclides likely to appear in drinking water following a radiological contamination
incident9. DRLs are concentrations of radionuclides in drinking water that correspond to
EPA's proposed PAG of 100 mrem and 500 mrem. DRLs are essential because a PAG
identifies a radiation dose rather than a quantity of radionuclides that can be measured
directly in drinking water. DRLs are expressed in units of picocuries per liter (pCi/L) or
becquerel per liter (Bq/L), and can be directly compared to measured radionuclide
concentrations in finished drinking water. In the absence of site-specific DRLs
developed by emergency responders acquainted with local conditions, EPA
recommends using these DRLs, which are indicative of a worst case scenario in which
there is no decay of isotopes over the exposure period, to guide actions to protect the
public in the event of a radiological incident that affects drinking water sources.
9 EPA selected 1-131, Sr-90/Y-90, and Cs-137 as indicator isotopes likely to appear in water following a
radiation contamination incident, these were selected based on previous documented experience.

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3.0 FACTORS EPA CONSIDERED WHEN ESTABLISHING THE
DRINKING WATER PAG
Section 1.3.2 of the revised interim PAG manual (2013)10 provides the following three
principles for establishing PAGs.
1.	Prevent acute effects
2.	Balance protection with other important factors and ensure that actions result in
more benefit than harm
3.	Reduce risk of chronic effects
EPA crafted the drinking water PAG with these same principles in mind. Specifically,
consideration was given to the acute effects of exposure to radiation and lifetime risk of
cancer based on age and drinking water intake. EPA made use of the risk conversion
factors set forth in Federal Guidance Report No. 13 (FGR-13)11 and considerations of
risk to the unborn set forth in National Council on Radiation Protection and
Measurements (NCRP) Report No. 174.12
In preparing this proposal, EPA gave careful consideration to public feedback received
on the revised interim PAG manual (2013) request for comments on adopting a drinking
water PAG.13
This proposed drinking water PAG was developed based on reducing risks associated
with ingesting drinking water contaminated with radionuclides. EPA also considered the
potential radiation dose people could receive from various other uses of contaminated
water, including showering, bathing, and dishwashing. In the United States, people
typically shower, bathe, and wash dishes using the same source of water that they use
to drink, but, for the radionuclides of interest, dermal and inhalation exposures from
these activities generally represent much smaller risk than drinking contaminated water.
Protection of a community's drinking water supply based on assumptions about
ingestion will also protect the population from undue risk from contaminated drinking
water by other routes of exposure.
10	EPA. 2013. Draft PAG Manual for Interim Use and Public Comment. Available online at:
http://www2.epa.gov/sites/production/files/2014-ll/documents/pag-manual-interim-public-comment-4-2-2013.pdf.
11	EPA. 1999. Cancer Risk Coefficients for Environmental Exposure to Radionuclides. Federal Guidance
Report #13. Available online at: http://www.epa.gov/rpdweb00/docs/federal/402-r-99-001.pdf.
12	Brent, R.L., Frush, D.P., Harms, R.W., and M.S. Linet. 2013. Preconception and Prenatal Radiation
Exposure: Health Effects and Protective Guidance. National Council on Radiation Protection. Report #174.
13	Public feedback on the draft PAG Manual was requested in the Federal Register Notice Vol. 78, No. 72,
p. 22257, April 15, 2013.
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4.0 RATIONALE FOR A TWO-TIER DRINKING WATER PAG
The two-tier PAG consists of 500 mrem for the general population (i.e., anyone over
age 15, excluding pregnant women and nursing women), and a more stringent PAG of
100 mrem to inform protective actions for pregnant women, nursing women and children
age 15 and under. Fetuses, infants and children are at greater risk from radiological
exposures than adults due to the greater sensitivity of the developing body to the
potential harmful effects of radiation and the longer dose commitment period for the
longer-lived radionuclides that clear slowly from the body. A newborn that ingests
radioactive material in water would be expected to be subject to the effects of that
radiation for a longer period of time than if the same dose was experienced by an adult.
There are precedents for establishing a more protective threshold for radiological risks
for younger members of the population due to the greater radiosensitivity of children
versus adults. Following the Fukushima nuclear plant releases in 2011, the Japanese
authorities set an emergency drinking water standard for infants that was one-third of
the value for adults.14
PAGs and other guidance materials established by FDA for thyroid blocking with
potassium iodide15 and for ingestion of food16 both include separate thresholds for more
sensitive age groups.
For the sake of establishing clear and executable decisions in the intermediate phase of
emergency response, EPA proposes a uniform PAG for fetuses, infants, and children,
even though there may be considerable differences in the transmission of radiological
drinking water contaminants to a fetus via the placenta, to an infant via formula, and to a
child via direct consumption. Specifically, we have proposed a PAG level designed to
protect the most sensitive of the three subgroups from exposure to radioactivity in
drinking water following a radiological incident. Keeping PAGs relatively simple helps to
minimize confusion during their implementation. Therefore, DRLs provided in Section
7.0 were selected by assessing risks to all age groups and choosing the most
conservative concentration to the most sensitive age group.
14	World Health Organization (WHO). 2011. FAQs: Japan nuclear concerns. Page 9, water contamination.
September 2011. Available online at: http://www.who.int/liac/crises/ipn/faas/en/index8.html.
15	FDA. 2001. Guidance: Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies.
Available online at: http://www.fda.gOv/downloads/Drugs/.../Guidances/ucm080542.pdf.
16	FDA. 1998 Accidental Radioactive Contamination of Human Foods and Animal Feeds:
Recommendations for State and Local Agencies.
http://www.fda. gov/downloads/MedicalDevices/.../UCM094513.pdf
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The PAG of 500 mrem for the general population is designed to be used in concert with
the FDA food PAG17 since many of the considerations for a food PAG also apply to
drinking water. It is also consistent with the guidance value of 500 mrem over one year
established by the Department of Homeland Security as an intermediate-phase PAG for
drinking water interdiction.18 A PAG of 100 mrem provides the most sensitive members
of the population a reasonable level of protection from exposure to radioactivity in
drinking water following a radiological incident.
4.1 Other Standards
The current public radiation protection standard of 100 mrem per year effective dose is
set forth in Nuclear Regulatory Commission (NRC) regulations (i.e., 10 CFR Part
20.1301). The International Commission on Radiation Protection19 recommends
reference levels in the range of 2,000 to 10,000 mrem (20 to 100 mSv) for protection of
human health in emergencies, and in the range of 100 to 2,000 mrem (1 to 20 mSv) for
occupational exposure, exposure by caregivers, or residential radon exposure. Based
on a risk reduction approach EPA is proposing its drinking water PAGs at the lower
(more stringent) end of the latter range as an added layer of precaution.
Following the Fukushima nuclear plant releases in 2011, there was concern about
levels of radioactive iodine-131 (1-131) in drinking water. The Japanese authorities
applied a two-tier set of provisional emergency standards to 1-131 in water: 300 Bq/L
(about 8,100 pCi/L) for adults and 100 Bq/L (about 2,700 pCi/L) for infants (specifically
for drinking water used to prepare baby formula). According to informational materials
assembled by the World Health Organization in the wake of the incident,20 these
emergency drinking water standards were provisional regulation values established by
the Japanese Food Sanitation Act, as indicated by the Nuclear Safety Commission of
Japan. These standards were precautionary and took international guidance into
consideration, including recommendations of the International Atomic Energy Agency
and the International Commission on Radiological Protection. The infant standard,
furthermore, was equivalent to the international guideline set by Codex Alimentarius21
for infant food.
Under the Safe Drinking Water Act (SDWA), EPA established maximum contaminant
levels (MCLs) for radiological contaminants in drinking water. The National Primary
Drinking Water Regulations (NPDWR) for radionuclides, set forth in 40 CFR Part 141,
17	FDA. 1998 Accidental Radioactive Contamination of Human Foods and Animal Feeds:
Recommendations for State and Local Agencies.
http://www.fda. gov/downloads/MedicalDevices/.../UCM094513.pdf
18	See Planning Guidance for Protection and Recovery Following Radiological Dispersal Device (RDD)
and Improvised Nuclear Device (IND). Table 1 in 73 FR 45029, August 2008, http://www.gpo.gov/fdsvs/pkg/FR-
2008-08-01/pdf/E8-17645. pdf.
19	International Commission on Radiological Protection (ICRP). 2007. The 2007 Recommendations of the
International Commission on Radiological Protection, Annals of the ICRP, Volume 37, Nos.2-4, 2007, Publication
103, ISSN 0146-6453, ISBN 978-0-7020-3048-2, pp. 96-98
20	WHO. 2011.
21	http://www.codexaiimentarins.org/abont-codex/eti/.
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effectively adopt a dose-based limit of 4 mrem/yr for beta particle and photon
radioactivity. These requirements are based on lifetime exposure criteria, which assume
70 years of continued exposure to contaminants in drinking water. The Agency
determined that it may not be appropriate to base protective actions during short-term
emergency incidents on lifetime exposure criteria. While the SDWA framework is
appropriate for day-to-day normal operations, it does not provide the necessary tools to
assist emergency responders with determining the need for potentially ongoing
protective actions during the intermediate phase of a response. However, regardless of
the cause of an incident, EPA expects that the responsible party for any drinking water
system impacted during a radiation incident will take action to return to compliance with
the NPDWR levels by the earliest feasible time.
5.0	INTERPRETING AND APPLYING THE PAG
The drinking water PAG is intended primarily to guide planning and decision-making
efforts by local and state officials, including drinking water providers, during the
intermediate phase of a radiological emergency when surface water sources are
particularly vulnerable to contamination from deposition of radioactive material from the
atmosphere. Actions to protect water sources may be implemented at other levels and
at any time following a radiological incident, and even before an anticipated release
occurs. The goal is to keep the dose to the public as low as reasonably achievable.
Radiation doses should be reduced to below SDWA MCLs as soon as practicable.
5.1	Interpreting the two-tier PAG
EPA is proposing a two-tier PAG: 500 mrem for the general population (anyone over
age 15, excluding pregnant women and nursing women) and 100 mrem for pregnant
women, nursing women and children.
Authorities have flexibility on how to apply the PAG. In some cases they may find it
prudent to use the PAG of 100 mrem as a target for the whole population, while in other
circumstances, authorities may find that it makes sense to use both targets
simultaneously. For example, emergency managers can use a two-tiered approach to
focus on protecting the most sensitive population with limited alternate water resources.
If bottled water must be rationed, for example, authorities may make the bottled water
available to children, pregnant women and nursing women, and instruct the rest of the
population to use a public drinking water supply that will not trigger the 500 mrem PAG.
As stated above, the PAGs are intended as guidance, and local authorities should take
into account local circumstances (e.g., incident scope and community needs) when
implementing a course of action to protect the public.
5.2	Operationalizing PAGs as Derived Response Levels (DRLs)
The PAG specifies a radiation dose to avoid via drinking water exposure projected over
one year. In order to determine whether a PAG should be implemented, authorities will
need to establish a relationship between the measured concentration of one or more
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radionuclides in finished drinking water and the radiation dose members of the
population might experience as a result of drinking contaminated water. Incident-
specific factors that may be taken into consideration include:
1.	The radionuclides being emitted in this particular emergency situation
2.	The rate and timing of entry of the radionuclides into a drinking water supply, via
atmospheric deposition or by other means
3.	The rate of natural attenuation of the radionuclides
4.	The estimated potential duration of public exposure to contaminated drinking
water
5.	The estimated daily consumption of contaminated drinking water
Those responsible for implementing PAGs will need to convert PAGs into Derived
Response Levels (DRLs) in units of Bq/L or pCi/L. Section 7.0 of this document
provides DRLs and explains how they can be calculated. Selected dose conversion
factors and standard estimates of daily drinking water consumption for various age
groups are also provided, along with references to informational resources.
While the PAG Manual is primarily for advance planning, there are specific
radionuclides, including cesium-137 (Cs-137), iodine-131 (1-131) and strontium/yttrium-
90 (Sr-90/Y-90) that are of particular interest for radiological incident scenarios where
drinking water sources might be contaminated. Section 7.0 presents default DRLs for
these radionuclides to aid emergency managers in making water restriction decisions
involving these contaminants. DRLs for these radionuclides are presented as examples
for purpose of illustration. If other radionuclides are present, DRLs should be calculated
using the same methodology, as discussed in Section 7.0.
5.3 Practical Considerations
After deposition has ended, radionuclide concentrations present in a water supply may
decline at rates determined by half-lives of the individual nuclides, or may decline faster
by dilution with uncontaminated water, or may even increase after rainfall and seasonal
thaw events. The concentration of radionuclides in drinking water as a function of time
after the incident can be measured, estimated or modeled based on knowledge of the
incident, including radionuclide sources and the properties of the drinking water supply.
Such estimates should be validated by monitoring or sampling, as discussed in Section
6.1.
Unlike naturally-occurring radionuclide contamination of drinking water from minerals
present in geological formations, for a radiation release incident, ground water sources
are expected to be less vulnerable to contamination than surface water sources, but this
should be confirmed by monitoring or sampling. The potential for ground water to
become contaminated will greatly depend on whether the ground water resource is
close to the surface or is from a deep aquifer bounded by an aquitard, as well as on
rainfall rate and the composition of the overlying soil (which will affect the rate at which
contaminants deposited on soil will migrate to the ground water resource).
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Section 6.3 discusses actions that authorities can take to minimize radiation doses from
drinking water. Because radionuclides decay over time, early interventions such as
restricting use of contaminated water immediately after the incident may be most
effective in reducing radiation dose to the population. Such decisions may need to be
made based on limited information. Authorities may find it prudent to take such action
even before field sample measurements or modeled estimates of radiation dose have
been calculated and validated.
6.0	PLANNING AND TAKING ACTION
This section discusses actions that state and/or local authorities and drinking water
utilities can take to protect the public in the event that a water supply is affected by a
radiological contamination incident. Different actions described here may be appropriate
for initial and intermediate phases depending on local resources. This section does not
constitute a complete handbook for radiological emergency response, but it describes
considerations that can be included in comprehensive emergency planning at the state,
local and utility level. Actions that public authorities and drinking water providers should
take include water monitoring (described in Section 6.1), public notification (described in
Section 6.2), and mitigation measures to protect the water supply and the water-
consuming public (described in Section 6.3).
Preventive action, such as temporary closure of water system intake valves to prevent a
contaminant plume from entering the system, may be taken in advance of an
anticipated release; it is not necessary to wait until drinking water contamination is
detected. Emergency response plans need to consider whether sufficient storage
capacity is available to support the community's fire suppression and sanitation needs
while the intake valves are closed.
Emergency planning provides the opportunity to develop state, local and utility-specific
plans and implementation procedures that reflect the unique needs of a particular
community. Advance planning can provide clarity and facilitate the decision-making
process during a radiological emergency.
6.1	Monitoring and Characterization of Contaminants
A comprehensive radiological surveillance program to monitor concentrations of
radionuclides of interest in both source water and finished drinking water would provide
an indication of whether any adjustments are necessary or if the actions being taken are
effective.
The NPDWR for radionuclides requires community water systems (CWSs) to conduct
monitoring at each entry point to the distribution system to ensure that every customer's
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water does not exceed the MCLs for radionuclides.22 All CWSs are required to monitor
for gross alpha, radium-226/228, and uranium. In addition, CWSs designated by the
state as "vulnerable"23 and those using waters "contaminated"24 by effluents from
nuclear facilities must also conduct monitoring for beta particle and photon radioactivity.
If a water system is directed by the primacy agency to collect samples for compliance
purposes, approved analytical methods must be used.
In the event of a radiological contamination incident, state officials may require public
water systems to immediately collect additional samples for radionuclides, including
beta particle and photon activity. However, EPA recognizes that during an emergency
situation it may be necessary to identify alternative sampling and analytical approaches
to obtain data to inform short-term actions by emergency response personnel. Many
states have established Radiological Emergency Preparedness25 programs designed to
guide sample collection and analysis and to advise emergency managers in a
radiological emergency. Additionally, the Federal Radiological Monitoring and
Assessment Center (FRMAC)26 can deploy monitoring and sampling field teams and
provide dose assessment expertise to assist states and local communities in
responding to an emergency. See the National Response Framework,
Nuclear/Radiological Incident Annex27 for information on roles and capabilities.
Once the situation is better characterized and systems are working towards returning to
compliance, monitoring should be conducted at entry points to the distribution systems
using approved analytical methods. EPA provides rapid laboratory analysis methods for
selected radionuclides to expedite the analytical turnaround time while simultaneously
meeting measurement quality objectives.28 Samples should be collected from entry
points to the distribution system. Challenges may arise from variability in environmental
matrices. Advance emergency planning can help to achieve sample representativeness
and homogeneity relative to routine samples.
If members of the public are served by drinking water from household cisterns or private
wells, local officials should consider how monitoring should be undertaken to determine
levels of target radionuclides and assess the risks posed to these populations.
22	For more information about monitoring requirements for the Radionuclides Rule see the "Radionuclides
Rule: A Quick Reference Guide" (EPA 816-F-01-003, June 2001) or "Implementation Guidance for Radionuclides"
(EPA 816-F-00-002, March 2002).
23	For more information see 40 CFR 141.26(b)(1).
24	For more information see 40 CFR 141.26(b)(2).
25	http://www.fema.gov/radiological-emergency-preparedness-program
26	The Federal Radiological Monitoring and Assessment Center (FRMAC) is a federal asset available on
request by the Department of Homeland Security (DHS) and state and local agencies to respond to a nuclear or
radiological incident.
27	Document is available online at: http://www.fema.gov/media-library/assets/documents/25554
28	EPA. 2014a. Rapid Radiochemical Methods Applicable to Selected Radionuclides for Environmental
Remediation Following Radiological Incidents. Third Edition. Front matter available online at:
http://www.epa.gov/narei/Docs/Preface%20to%203rd%20Edition%20%280niine%29%200'	pdf. Rapid
methods are available online at: http://www.epa.gov/narel/rapid_methods.html
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6.2	Public Notification
An emergency response plan should include a strategy for keeping the community
informed of the actions being taken by authorities and clearly delineate roles and
responsibilities of local officials and emergency responders. This includes
communicating to customers of CWSs and (if applicable) to those who rely on
household cisterns and private wells. It is critical for water utilities to participate in the
emergency response planning activities.
If compliance monitoring indicates that contamination levels exceed the MCL for any
radionuclide, water systems are required to issue public notice on a "Tier 2" time frame
(i.e., as soon as practical, but no later than 30 days after the system learns of the
violation). CWSs should be able to issue repeat notices as required. However, states
may determine that the notification requirement should be elevated to a "Tier 1" Public
Notification (i.e., as soon as practical, but no later than 24 hours) based on a significant
potential for serious adverse effects on human health due to short-term exposure.29
During a response to a radiological incident, water systems may have difficulty with
issuing public notifications in addition to managing the response to the contamination
event. The state may issue public notification on behalf of the water system (40 CFR
141.210(a)). This would allow the state to deliver a consistent message to all affected
customers and allow the system to concentrate its efforts on returning to operation or
returning to compliance in the event of a radionuclides MCL violation. For more
information see the Revised Public Notification Handbook (EPA 816-R-09-013, March
2010).
State and local authorities should be proactive in communicating about risks and
uncertainties and providing clear instructions to the public. For any incident response
requiring coordinated federal support, refer to the National Response Framework and
Emergency Support Function 15, External Affairs Annex, for roles and response
protocols.
6.3	Additional Actions to Reduce Levels of Contamination
In the initial phase following a radiological incident, officials should take reasonable
precautionary measures (i.e., closing intake valves) to protect water sources as soon as
notification of a radiological release or impending release is received. Moving into the
intermediate phase, as data are obtained from monitoring programs (including sampling
and analysis of water upstream and downstream of a water system intake structure and
within the distribution system), officials should benchmark observed concentrations
against the default DRLs discussed in Section 7.0 or situation specific DRLs that
account for specific isotopes present, release patterns, and decay. Officials would then
be in a position to make informed decisions about the need to implement protective
29 For more information see 40 CFR 141.202(a), Table 1(9), Special public notices: Occurrence of a
waterborne disease outbreak or other waterborne emergency.
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actions. Water system officials should be in close communication with their primacy
agency (e.g., state/county regulators) prior to taking protective actions.
Options available to water systems to reduce radiation dose to drinking water customers
include applying treatment technologies, relying on back-up storage, blending water,
accessing alternative water sources, and rationing of uncontaminated water or a
combination of these actions. Examples of these options are described briefly below.
Technical and economic burden on smaller systems may be reduced by pooling
resources with other water systems (e.g., establishing interconnections, sharing
technical and operator staff, and sharing of supplies and equipment). As part of
emergency planning efforts, local officials should consider the possibility of temporary
rationing of uncontaminated or treated water if supplies are inadequate to meet normal
demand.
All of these options require advanced planning and should be evaluated and included in
States plans as appropriate. Guidance on developing emergency drinking water
supplies is available from EPA.30 The Centers for Disease Control and Prevention also
provide resources and guidance for establishing emergency water supplies and
communicating water advisories to the public.31
6.3.1 Treating Contaminated Water
Systems can treat contaminated water to reduce elevated radionuclide levels. Four
treatment technologies are classified by EPA as Best Available Technologies (BATs) for
removing radionuclides from drinking water: coagulation/filtration, ion exchange, lime
softening and reverse osmosis. EPA has also listed these BATs as Small System
Compliance Technologies (SSCTs) for radionuclides treatment, along with less
commonly used techniques such as green sand filtration, co-precipitation with barium
sulfate, electrodialysis/electrodialysis reversal, pre-formed hydrous manganese oxide
filtration and activated alumina. Further information on radionuclide treatment options is
available from EPA.32
Removal efficiency for specific radionuclides will vary across available technologies and
may depend on technology-specific parameters (e.g., ion exchange effectiveness
depends on pH, resin selected and presence of other ions). In addition, liquid and solid
treatment residuals with elevated radiation levels may have special disposal
30	EPA. 201 lb. Planning for an Emergency Drinking Water Supply, EPA 600/R-l 1/054, June 2011.
31	CDC. 2014. Drinking Water Advisory, Planning, & Emergency Response Resources. Available on the
Internet at: http://www.cdc.gov/healthvwater/emergencv/drinkingwateradvisory.html. Last updated December 2,
2014.
32	EPA. 2015a. Radionuclides in Drinking Water ~ Compliance Options: Treatment Technology
Descriptions. Available on the Internet at: http://cfpnb.epa.gov/safewater/radionnclides/radionndides.cfm. See also
EPA. 2002a. Radionuclides in Drinking Water: A Small Entity Compliance Guide. EPA 815-R-02-001, 2002.
(http://www.epa.gov/safewater/radionnclides/pdfs/giiide radionuclides smattsvstems compliance.pdf).
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requirements. Disposal options may vary from one jurisdiction to another, and may
depend on the type, concentration and volume of residuals. Further information on
residual disposal considerations is available from EPA.33
6.3.2	Temporarily Closing Intake Valves
If the deposition of radionuclides into a river is limited in duration, only a portion of the
water may become contaminated. A water system with enough storage capacity can
temporarily close its intake valves and allow the contaminants to flow past the intake to
prevent contamination from entering the distribution system.
If stored water supplies are not sufficient to meet community fire suppression and
sanitation needs while intake valves are closed, the system could take other actions
discussed in this section, including supplementing water supplies with alternate sources
or implementing water use restrictions.
6.3.3	Establishing Interconnections to Neighboring Systems
If the water system is part of a larger, regional supply system, existing interconnections
to an uncontaminated neighboring water supply could be activated. It might also be
possible to construct temporary pipelines on an impromptu basis.
If this option is implemented, steps should be taken to prevent backflow from the
contaminated system. Care will also need to be taken to ensure that the supply of water
and treatment capacity at the uncontaminated system will adequately serve the larger
population.
6.3.4	Blending Water Sources
If a source of uncontaminated water is available, a water system may choose to blend
water from contaminated and uncontaminated sources of drinking water to minimize
radiation doses from drinking water. The water may be blended using storage tanks or a
common header to allow for complete mixing prior to distribution to customers.
6.3.5	Importing Water in Tanker Trucks
Under some circumstances (e.g., difficult terrain, urgent need), it may be more efficient
or expedient to temporarily transport clean water by truck, rail or barge to distribution
centers in the affected community than to lay down pipelines. State and local
departments of public health, as well as emergency management agencies, typically
have standards and requirements related to hauling water. Water systems would benefit
from having procedures for importing water in tanker trucks documented in an
emergency response plan. All water systems importing water by tanker should verify
that their plan adheres to state and local requirements. If the water system's distribution
33 EPA. 2006a. A System's Guide to the Management of Radioactive Residuals from Drinking Water
Treatment Technologies. EPA 816-F-06-012, August 2006. See also EPA. 2006b. A System's Guide to the
Identification and Disposal of Hazardous and Non-Hazardous Water Treatment Plant Residuals. EPA 816-F-06-
011, August 2006.
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system is not being used to provide the imported water, the needs of residents with
limited transportation options and physical disabilities should be taken into account
when selecting locations for distribution centers. The availability of suitable transport
vehicles may limit use of this option.
6.3.6 Importing Bottled Water
Providing bottled water to the affected community is another possible option during an
emergency situation. The water may come from a nearby water system or from a water
bottling company. This option may be cost-effective during an emergency if water is
needed quickly and if the length of the emergency does not require long-term action,
such as the construction of an interconnecting pipe.
7.0 DERIVED RESPONSE LEVELS (DRLS)
EPA developed the radionuclide-specific default DRLs by calculating the radionuclide
concentrations in drinking water that would result in projected radiation doses of 100
and 500 mrem, assuming one year of continuous exposure and average drinking water
intake rates for children and adults.
Several considerations should be kept in mind when using these pre-calculated DRLs.
The DRLs presented in Table 1 are calculated on the assumption that each radionuclide
is the only radionuclide present in drinking water. DRLs are additive. In situations where
multiple radionuclides are present, DRLs should be combined using a sum of fractions
approach to ensure that the projected dose does not exceed the PAG of 100 or 500
mrem. (An example calculation is provided in Section 7.1.) Table 1 does not present
DRLs for all radionuclides that may occur in drinking water following a contamination
incident.
These default DRLs were calculated using a simplifying and conservative assumption
that radionuclide levels will remain constant over the course of one year. This
assumption would cover the most serious situations in which continuous release and
replenishment of isotopes is ongoing. As such, the assumption provides an added level
of protection in light of the many unknowns involved in an emergency. In fact, after the
initial deposition event has occurred, concentrations may decline at rates determined by
the half-lives of individual isotopes, or decline faster due to dilution with uncontaminated
water, or could even increase after rainfall or subsequent deposition events. Some
nuclides, like 1-131, have half-lives measured in days, while others, like Cs-137, have
half-lives measured in years.
The default DRLs in the PAGs are provided for convenience to allow local entities to
make decisions about drinking water provided by public water systems quickly in the
event of a radiological emergency. As one moves further into the intermediate phase,
when the incident characteristics have been assessed, assumptions regarding duration
of the radiological release and the half-life of nuclides involved as well as other factors
may be considered by local decision makers in projecting risks and adapting mitigation
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measures. All radionuclides are covered by the assessment tools provided by FRMAC.
For instance, if an alpha emitting isotope was of concern following a radiation
contamination incident, it would be included in any calculations regarding protective
actions for drinking water. As such, local officials may choose to work with FRMAC to
calculate situation-specific DRLs that are based on information gained during the
intermediate phase, including identification of specific isotopes, release patterns, and
associated decay functions.
Early exceedance of the default DRL does not preclude the possibility that doses will
stay below PAGs as radionuclide concentrations in water decline by a combination of
radioactive decay and natural attenuation. If the concentrations of radionuclides do not
exceed DRLs over the course of one year, doses will remain below the PAG.
Table 1. Default derived response levels (DRLs)34 -- drinking water concentrations
corresponding to specified doses (mrem) of select radionuclides, assuming one
year of exposure at constant levels35

DRLs for pregnant women,
nursing women and children
age 15 and younger - 100
mrem dose
DRLs for adults (excluding pregnant
women and nursing women) - 500
mrem dose

Sr-90/Y-9036
1,000 pCi/L
7,400 pCi/L
Cs-137
6,140 pCi/L
16,570 pCi/L
1-131
1,310 pCi/L
10,350 pCi/L
The DRLs provided in Table 1 were derived by calculating life stage-specific DRLs (as
described in section 7.2) for six different ages (Infant, 1, 5, 10, 15, and adults). For the
most sensitive life-stages concentrations of individual radionuclides yielding a 100 mrem
dose were calculated for each age group, then the most protective/lowest radioactivity
concentration was selected as the DRL for the entire sensitive life-stage group,
including pregnant and nursing women. The calculated values differ across individual
34	Values provided in this table have been rounded.
35	The calculated values provided in this table are intended to illustrate the methodology and conservative
assumptions EPA believes are adequate to provide a reasonable level of protection to sensitive populations. Dose
conversion factors, calculation methodologies as well as other comprehensive information regarding DRL
development will be available and updated as needed in the FRMAC Assessment Manual.
36	Y-90 is a radioactive decay product of Sr-90 and will normally be found alongside Sr-90 in the case of a
Sr-90 release; therefore they are treated together. Solubility differences may cause less yttrium to be present,
however it is a conservative assumption to include both in DRLs. When calculating the combined DRL, note that the
dose coefficients (see Table 3) are additive.
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life-stages because each age group has a different dose conversion factor and drinking
water ingestion rate.
For example, the sensitive life-stage group DRL for 1-131 was derived by calculating the
concentration of 1-131 which yields a 100 mrem dose for each age group. In this case
the resulting concentrations were: infants (2,110 pCi/L), 1 yr (1,860 pCi/L), 5 yr (1,310
pCi/L), 10 yr (1,950 pCi/L), and 15 yr (2,410 pCi/L). Since the lowest calculated
concentration corresponds to the 5 year old (1,310 pCi/L), this value is the DRL that will
be applied to be the most protective for the entire sensitive life-stage group.
7.1 Calculation of Default DRLs
DRLs may be calculated with the help of the following equations.
The dose (mrem or Sv) due to the ingestion of radionuclide /' to age group a over time
period T is calculated as follows:
DiaT = liaT* DCFia
Where:
DiaT = Dose (in mrem or Sv) due to the ingestion of radionuclide /' to age group a
over time period T
liaT = The total intake of radionuclide /' for age group a (in pCi or Bq) over time
period T
DCFia = The dose conversion factor (also referred to as dose coefficient) for the
ingestion of radionuclide /' in drinking water and age group a (in mrem/pCi or
Sv/pCi, or mrem/Bq or Sv/Bq). See section 7.4 for guidance on DCFs.
The quantity of radionuclide /' ingested by age group a over a given time period, T, is
calculated as follows.
liaT = Ci x Inga x T
Where:
liaT = The total intake of radionuclide /' for age group a (in pCi or Bq) over time
period T.
Ci = The concentration of radionuclide /' in drinking water (in pCi/L or Bq/L). A
simplifying assumption is made that the concentration of the radionuclide is
constant over the time period T.
Inga = The daily ingestion rate of water for age group a, in L/day. See Section 7.3 for
guidance on daily water ingestion rates.
T = The time period that the population is drinking contaminated water (days). In
this analysis, the time period of interest is 365 days.
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For each age group a and radionuclide /', substituting the applicable PAG for the dose
DiaT and then solving for Ci yields the applicable DRL.
For example, the DRL for iodine-131 for an adult is calculated as follows:
DRL = PAG / (lnga * T * DCFia)
DRL = 500 mrem / (1.643 L/day * 365 days * 8.05 E-05 mrem/pCi)
= 500/4.83 E-02
= 10,352 pCi/L
Which is best rounded to 10,350 pCi/L considering the uncertainties.
7.2 Combining default DRLs for Multiple Radionuclides
If multiple radionuclides are present in the water supply, then it is recommended that the
obtained concentrations of each radionuclide be divided by the provided DRL values.
This provides a fraction of the allowed concentration (and the projected dose) for each
radionuclide. If the sum of the fractions is less than 1, the total dose is assumed to be
below the PAG values. Emergency response personnel may need to calculate the sum
of fractions on an ongoing basis, as the concentrations of individual radionuclides may
change over time. The sum of the fractions is expressed as follows:
F = X (Ci / DRL)
Where:
F = sum of the fractions
Ci = the concentration of radionuclide /' in the water supply (pCi/L or Bq/L)
DRLi (ioo or 500 mrem); = derived response level for the ith radionuclide (pCi/L or Bq/L)
For example, if Sr-90/Y-90 and Cs-137 are the only radionuclides present in the drinking
water, and Sr-90/Y-90 are present at 1,540 pCi/L and Cs-137 is present at 10,600
pCi/L, the combined dose exceeds the PAG of 100 mrem for fetuses, infants, and
children:
F = Z (Ci / DRL)
= (1,540 pCi/L /1,000 pCi/L) + (10,600 pCi/L / 6,140 pCi/L)
= 1.54 + 1.73
= 3.27
3.27 > 1, so the PAG is exceeded.
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The same concentrations do not exceed the PAG of 500 mrem for adults:
F = X (Ci / DRL)
= (1,540 pCi/L / 7,415 pCi/L) + (10,600 pCi/L /16,570 pCi/L)
= 0.21 +0.64
= 0.85
0.85 < 1, so the PAG is not exceeded.
7.3 Water Ingestion Rates
Table 2 presents mean values for tap water consumption taken from the CD
supplement to FGR-13.37 Other sources of estimated drinking water ingestion rates are
available (e.g., EPA's Exposure Factors Handbook38), but the ingestion rates presented
in FGR-13 were specifically designed with corresponding age ranges to be used in
conjunction with other data from FGR-13. Values are provided for males and females in
various age groups. Since the ingestion rates for males are higher (and therefore more
conservative) than those for females, EPA elected to use the intake values for males to
represent each age group in the calculation of DRLs in Table 1. In addition, for the
calculation of the adult DRL, EPA made the conservative assumption that the ingestion
rate would be assigned the highest value within the adult category, the 50 year old
male, at an estimated 1.643 L/day.
Table 2. Mean Drinking Water Ingestion Rates from FGR-13
Age (years)
Tap Water (L/day)
Male
Female
0
0.191
0.188
1
0.223
0.216
5
0.542
0.499
10
0.725
0.649
15
0.900
0.712
20
1.137
0.754
50
1.643
1.119
75
1.564
1.179
Source: CD Supplement to FGR-13, Table 3.1.
37	EPA. 2002b. Federal Guidance Report 13. Cancer Risk Coefficients for Environmental Exposure to
Radionuclides: CD Supplement, EPA-402-C-99-001, Rev. 1.
38	EPA. 2011a.
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7.4 Dose Coefficients, or Dose Conversion Factors (DCF) (Sv/Bq Ingested)
The effective whole body dose per Bq ingested of various radionuclides in water, for
various age groups, can be found on the CD supplement to FGR-13.39 These DCF
values apply to both males and females. Table 3 presents DCFs for a few
representative radionuclides of interest, converted to U.S. units for convenience.
Table 3. Dose Conversion Factors40
Age
DCFs (mrem per pCi ingested), from FGR-13
Sr-90
Y-90
Cs-137
1-131
Infant (100 day old)
8.40E-04
1.16E-04
7.79E-05
6.82 E-04
1 year old
2.68E-04
7.41 E-05
4.58E-05
6.62E-04
5 year old
1.73E-04
3.69E-05
3.58E-05
3.83E-04
10 year old
2.21 E-04
2.18E-05
3.75E-05
1.94 E-04
15 year old
2.92E-04
1.24E-05
4.95E-05
1.27E-04
Adult
1.02 E-04
9.94E-06
5.02E-05
8.05E-05
Source: CD Supplement 1
o FGR-13.
39	EPA. 2002
40	The DCFs in this table show the variation across age groups and nuclides and are provided to illustrate
the conservative methodology and assumptions EPA believes are adequate to provide a reasonable level of
protection to sensitive populations. Additional information including updated dose conversion factors, calculation
methodologies as well as other comprehensive information regarding DRL development will be appended to the
FRMAC Assessment Manual.
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