|
 |
|
National Primary Drinking Water Regulations;
Radon-222 [[pp. 59295-59344]]
Federal Register Document
Related Material
[Federal Register: November 2, 1999 (Volume 64, Number 211)]
[Proposed Rules]
[Page 59295-59344]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr02no99-36]
[[pp. 59295-59344]] National Primary Drinking Water Regulations; Radon-222
[[Continued from page 59294]]
[[Page 59295]]
In discussions between EPA and the water utility industry, concerns
have been expressed about the difficulties in collecting samples and
the requisite skills that may be required. EPA emphasizes that the
skills required to sample for radon are the same as those required to
sample for other currently regulated drinking water contaminants,
namely volatile organic contaminants. In addition, the 1992 EPA
collaborative study mentioned earlier evaluated four sample collection
techniques and found them all capable of providing equivalent results.
Supplementing this study, EPA has reviewed a sampling protocol for
radon in water developed by the Department of Health Services Division
of Drinking Water and Environmental Management (CA DHS 1998). This
protocol employs one of the four techniques evaluated by EPA, the
immersion technique.
Using the immersion technique, the well is purged for 15 minutes by
running the sampling tap, to ensure that a representative sample is
collected. After the purging period, a length of flexible plastic
tubing is attached to the spigot, tap, or other connection, and the
free end of the tubing is placed at the bottom of a small bucket. The
water is allowed to fill the bucket, slowly, until the bucket
overflows. The bucket is emptied and refilled at least once.
Once the bucket has refilled, a glass sample container of an
appropriate size is opened and slowly immersed into the bucket in an
upright position. Once the bottle has been placed on the bottom of the
bucket, the tubing is placed into the bottle to ensure that the bottle
is flushed with fresh water. After the bottle has been flushed, the
tubing is removed while the bottle is resting on the bottom of the
bucket. The cap is placed back on the bottle while the bottle is still
submerged, and the bottle is tightly sealed. As noted in the California
protocol cited earlier, the choice of the sample container is dependent
on the laboratory that will perform the analysis, and will be a
function of the liquid scintillation counter that is employed. If
bottles are supplied by the laboratory, there is no question of what
container to employ.
Once the sealed sample bottle is removed from the bucket, it is
inverted and checked for bubbles that would indicate headspace. If
there are no visible air bubbles, the outside of the sealed bottle is
wiped dry and cap is sealed in place with electrical tape, wrapped
clockwise. After the sample bottle is sealed, a second (duplicate)
sample is collected in the same fashion from the same bucket. The date
and time of the sample collection is recorded for each sample.
As can be surmised from the description, the sample collection
procedures are not particularly labor intensive. Most of the time is
spent allowing the water to overflow the bucket. Likewise, there are no
significant manual skills required.
(e) Skill Considerations for Laboratory Personnel. While neither of
these techniques is difficult relative to standard drinking water
methods, a discussion of the skills required to employ the methods is
appropriate. Given the long history of successful use of the liquid
scintillation counting technique (it has been used in medical
laboratories and environmental research laboratories for well over 30
years), EPA feels confident that State drinking water laboratories will
be able to adequately use these methods. The skills required are
primarily the ability to transfer and mix aliquots of the sample to a
sealed container for further analysis. The counting process is highly
automated and the equipment runs unattended for days, if needed.
The de-emanation process requires somewhat more manual skill. As
noted in the 1991 proposed rule, EPA expects that this technique would
require greater efforts be made to train technicians than for the
liquid scintillation technique. The technique requires that the
counting cell be evacuated to about 10 mTorr pressure and then a series
of stopcocks or valves are manipulated to transfer the radon that is
purged from the sample into the counting cell. Potential problems with
the analysis, such as a high background level of radon that can develop
over the course of the day, or aspirating water into the counting cell,
can be minimized by a well-trained analyst. However, as EPA concluded
in 1991, the Lucas cell technique is not expected to form the sole
basis of a compliance monitoring program for radon in drinking water.
(f) Cost of Performing Analyses. The actual costs of performing
analysis may vary with laboratory, analytical technique selected, the
total number of samples analyzed by a lab, and by other factors. Based
upon information collected in 1991, the average sample cost for radon
in water was estimated to be $50 per sample. EPA recently updated this
cost estimate to $57 per sample (USEPA 1999b) by conducting a similar
survey of drinking water laboratories. The data from the 1991 and 1998
surveys and the descriptive statistics are summarized in Table
VIII.B.2. There was no clear correlation between the estimated price
and the method cited by the laboratory. The 1998 range of prices
brackets those collected by EPA in 1991. It is expected that the
``market forces'' generated by a radon regulation will tend to lower
per sample costs, especially in light of the fact the LSC is very
amenable to automation, with feed capacities of more than 50 samples/
load possible. However, as will be discussed later, there may be short-
term laboratory capacity issues that resist a lowering of per sample
prices.
Table VIII.B.2. Radon Sample Cost Estimate
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Cost Year data
Arbitrary lab No. estimate collected Descriptive statistics for 1991
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1..................................... $30 1991 Mean, $49.80; Median, $47.00; Std. Dev., $18.80; Range, $45; Minimum, $30; Maximum, $75.
2..................................... 44 1991
3..................................... 50 1991
4..................................... 75 1998
Descriptive Statistics for 1998 Data
5..................................... 75 1998 Mean, $56.88; Median, $52.50; Std. Dev., $15.80; Range, $35; Minimum, $40; Maximum, $75.
6..................................... 50 1998
7..................................... 40 1998
8..................................... 75 1998
9..................................... 45 1998
10.................................... 55 1998
11.................................... 75 1998
12.................................... 40 1998
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 59296]]
These cost data are preliminary and may be different in practice
for the following reasons: (a) As the number of experienced
laboratories increases, the costs can be expected to decrease; (b)
analytical costs are determined, to some extent, by the quality control
efforts and quality assurance programs adhered to by the analytical
laboratory; (c) per-sample costs are influenced by the number of
samples analyzed per unit time. EPA solicits comments on its cost
estimates from laboratories experienced in performing these analyses.
(g) Method Detection Limits and Practical Quantitation Levels.
Method detection limits (MDLs) and practical quantitation levels (PQLs)
are two performance measures used by EPA to estimate the limits of
performance of analytic chemistry methods for measuring contaminants in
drinking water. An MDL is the lowest level of a contaminant that can be
measured by a specific method under ideal research conditions. EPA
usually defines the MDL as the minimum concentration of a substance
that can be measured and reported with 99 percent confidence that the
true value is greater than zero. The term MDL is used interchangeably
with minimum detectable activity (MDA) in radionuclide analysis, which
is defined as that amount of activity which in the same counting time,
gives a count which is different from the background count by three
times the standard deviation of the background count. A PQL is the
level at which a contaminant can be ascertained with specified methods
on a routine basis (such as compliance monitoring) by accredited
laboratories, within specified precision and accuracy limits.
The feasibility of implementing an MCL at a particular level is in
part determined by the ability of analytical methods to ascertain
contaminant levels with sufficient precision and accuracy at or near
the MCL. The proposed methods demonstrate good reproducibility and
accuracy at radon concentrations in the range of 150-300 pCi/L (half of
the proposed MCL up to the proposed MCL), as demonstrated in the
results from inter-laboratory studies. In inter-laboratory studies (or
Performance Evaluation studies), prepared samples of known
concentration are distributed for analysis to participating labs, which
have no information on the concentrations of the samples. The results
of the analyses by the participants are compared with the known value
and with each other to estimate the precision and accuracy of both the
methods used and the lab's proficiency in using the method. Table
VIII.B.3 summarizes the statistical results of these inter-laboratory
studies for the proposed methods.
In the 1991 proposed rule, EPA proposed using both the MDL and PQL
as measures of performance for radon analytical methods. EPA also
proposed acceptance limits based on the PQLs that were derived from
these performance evaluation studies. The use of acceptance limits was
confusing to commenters for various reasons. The important issue is the
observation that true analytical method performance is related to
within-laboratory conditions (including counting times in the case of
radiochemicals) and that acceptance limits are based on multi-
laboratory Performance Evaluation studies. For non-radiochemical
contaminants this issue is less troublesome because their PQLs tend to
be ``fixed'' since the MDLs to which they are related reflect optimized
conditions for standard laboratory equipment, whereas for radiochemical
contaminants, counting times can always be increased to increase the
sensitivity and hence lower the appropriate acceptance limits. While
the fifty minute counting time in Standard Method 7500-Rn reflects a
balanced trade-off between time of analysis (and hence the cost of
analysis) and sensitivity, it can obviously be adjusted as needed to
adjust sensitivity. For this reason, commenters objected to the use of
acceptance limits (and, relatedly, PQLs) for radiochemical
contaminants.
EPA agrees that these comments have merit and has decided to seek
comment on two proposals regarding the use of acceptance limits and
PQLs for radon. The first proposal, and the preferred option, is to not
use acceptance limits or PQL for radon, and to adopt the detection
limit as the measure of sensitivity, as done in the 1976 Radionuclides
rule. The existing definition of the detection limit takes into account
the influence of the various factors (efficiency, volume, recovery
yield, background, counting time) that typically vary from sample to
sample. Thus, the detection limit applies to the circumstances specific
to the analysis of an individual sample and not to an idealized set of
measurement parameters, as with acceptance limits and PQLs. The
proposed detection limit is 12 +/- 12 pCi/L, which is based on the
detection limit described in SM 7500-Rn (50 minute counting time, 6 cpm
background, 2.7 cpm/dpm efficiency, and under the energy window
optimization procedure as described in the method). This detection
limit should be applicable to all three approved methods.
One of the reasons for setting a sensitivity standard is to ensure
that laboratories will perform acceptably well on a routine basis at
contaminant levels near the MCL. Internal quality control/quality
assurance procedures are of paramount importance. In addition,
Proficiency Tests are administered by laboratory certifying authorities
to ensure that laboratory performance is acceptable. Currently, the
system for administering proficiency tests and certifying laboratories
is in a state of transition. Up to the recent past, all primacy
entities evaluated laboratory performance based on EPA's Performance
Evaluation (PE) studies program, the National Exposure Research
Laboratory (NERL-LV) Performance Evaluation (PE) Studies program for
radioactivity in drinking water. Currently, the Proficiency Testing
(PT) program for radionuclides is being privatized, i.e., operated by
an independent third party provider accredited by the National
Institute of Standards and Technology (NIST). A lack of uniformity in
state PT requirements may limit laboratory availability for a given
public water system to laboratories that use PT samples approved by the
state. It should be noted that this issue is general and is not
specific to the proposed radon regulation. Efforts to encourage
uniformity in state PT requirements are described in more detail in the
laboratory capacity section.
Under the alternative of using the MDL as the measure of
sensitivity, standard statistical procedures would be used to ensure
that a laboratory has analyzed PT samples acceptably. Since the
national PT program will still be overseen by EPA, the exact procedures
for determining acceptable performance will be developed by EPA and
NIST as the PT program develops. The respective roles of EPA and NIST
in the PT program and discussed further in the Laboratory Approval and
Certification section.
The second proposal is to use the concepts of the acceptance limit
and PQL for radon. Using the standard relationship that PQLs are equal
to 5 to 10 times the MDL yields a PQL for radon in the range of 60 to
240 pCi/L. EPA is proposing a PQL of 100 pCi/L and is seeking comment
on this value. The proposed acceptance limit for a single sample is
5 %. The proposed acceptance limits for triplicate analyses
at the 95th and 99th percent confidence intervals are 6 %
and 9 %, respectively. All of these acceptance limits are
based on the inter-laboratory studies used for the precision and
accuracy results reported in Table
[[Page 59297]]
VIII.B.3. EPA seeks comments on the relative merits between the first
option (the preferred option) of using only an MDL as the measure of
sensitivity and the second option of using a PQL with prescribed
acceptance limits.
Table VIII.B.3.--Inter-laboratory Performance Data for Proposed Radon Analytical Methods \1\
----------------------------------------------------------------------------------------------------------------
Sample
Method Conc. pCi/ Accuracy % Repeatability Reproducibility Bias %
L pCi/L pCi/Ls
----------------------------------------------------------------------------------------------------------------
SM 7500-Rn............................... 111 101-102 9 12 0.7-2.3
SM 7500-Rn............................... 153 102-103 10 16-18 2.3-3.4
De-Emanation............................. 111 114 16 23 14.5
De-Emanation............................. 153 114 17 28 13.7
ASTM D5072-92............................ 1,622 97 2,217 3,541 -2.6
ASTM D5072-92............................ 16,324 95 14,950 44,400 -4.7
ASTM D5072-92............................ 66,324 94 49,190 210,350 -6.0
----------------------------------------------------------------------------------------------------------------
Notes: (1) All results are reported in methods citations found in Table VIII.B.1.
(h) Accuracy and Precision of the Proposed Methods. While SM 7500-
Rn has the best over-all results in precision and accuracy, the de-
emanation method also shows acceptable performance. The ASTM method
shows similar accuracy and bias, but much larger errors in
repeatability (operator precision) and reproducibility (between-lab
precision). Given this inferior demonstration of precision and the
higher concentrations used in the intra-laboratory studies, it may be
argued that this method should not be proposed as a drinking water
method. However, EPA maintains that the method is similar enough in
substance to SM 7500-Rn that it may serve as an alternate method if the
laboratories use the appropriate quality control measures, i.e., ensure
that the relative percent difference between results on duplicate
samples is within the counting uncertainty 95% confidence interval,
where at least 10% of daily samples are duplicates. This procedure is
described in the 4th edition of the Manual for the Certification of
Laboratories Analyzing Drinking Water, Criteria and Procedures Quality
Assurance (EPA 1997). EPA requests comment on including ASTM D5072-92
as an alternate test method.
C. Laboratory Approval and Certification
1. Background
The ultimate effectiveness of the proposed regulations depends upon
the ability of laboratories to reliably analyze contaminants at
relatively low levels. The Drinking Water Laboratory Certification
Program is intended to ensure that approved drinking water laboratories
analyze regulated drinking water contaminants within acceptable limits
of performance. The Certification Program is managed through a
cooperative effort between EPA's Office of Ground Water and Drinking
Water and its Office of Research and Development. The program
stipulates that laboratories analyzing drinking water compliance
samples must be certified by U.S. EPA or the State. The program also
requires that certified laboratories must analyze PT samples, use
approved methods, and States must also require periodic on-site audits.
External checks of performance to evaluate a laboratory's ability
to analyze samples for regulated contaminants within specific limits is
one of the means of judging lab performance and determining whether to
grant certification. Under a PT program, laboratories must successfully
analyze PT samples (contaminant concentrations are unknown to the
laboratory being reviewed) that are prepared by an organization that is
approved by the primacy entity. Successful annual participation in the
PT program is prerequisite for a laboratory to achieve certification
and to remain certified for analyzing drinking water compliance
samples. Achieving acceptable performance in these studies of known
test samples provides some indication that the laboratory is following
proper practices. Unacceptable performance may be indicative of
problems that could affect the reliability of the compliance monitoring
data.
EPA's previous PE sample program and the approaches to determine
laboratory performance requirements are discussed in 63 FR 47097
(September 3, 1998, ``1998 methods update''). In that notice, EPA
amended the regulations to adopt the universal requirement for
laboratories to successfully analyze a PE sample at least once each
year, addressing the fact that the Agency has not specified PE test
frequency requirements in its current drinking water regulations.
Though not specified in the methods update regulation, PE samples may
be provided by EPA, the State, or by a third party with the approval of
the State or EPA. Under the developing PT program, NIST has accredited
a list of PT sample providers, including a radionuclides PT samples
which will apply to radon.
In addition, guidance on minimum quality assurance requirements,
conditions of laboratory inspections, and other elements of laboratory
certification requirements for laboratories conducting compliance
monitoring measurements are detailed in the 4th edition of the Manual
for the Certification of Laboratories Analyzing Drinking Water,
Criteria and Procedures Quality Assurance (EPA 1997), which can be
downloaded via the internet at ``http://www.epa.gov/OGWDW/
labindex.html''.
2. Laboratory Capacity--Practical Availability of the Methods
In order to determine the practical availability of the methods,
EPA considered three major factors. First, the availability of the
major instrumentation was reviewed. Secondly, several laboratories
performing drinking water analyses were contacted to determine their
potential capabilities to perform radon analyses. Lastly, EPA has
reviewed the current status of the privatized Performance Evaluation
studies program and the on-going measure to implement a uniform
program, highlighting the potential impacts on short-term and long-term
laboratory capacity for radon.
3. Laboratory Capacity: Instrumentation
Regarding instrumentation availability, the major instrumentation
required for LSC is the liquid scintillation counter. Automated
counters capable of what that method terms ``automatic spectral
analysis'' are available from at least a dozen suppliers. The de-
emanation Lucas cell apparatus is the same apparatus that has been used
for radium analyses for many years. In light of the wide availability
and the long history of accessibility of the proper instrumentation,
EPA believes that instrument availability should not be an issue for
radon analytical methods.
[[Page 59298]]
4. Laboratory Capacity: Survey of Potential Laboratories
In order to evaluate the availability of laboratory capacity to
perform radon analyses, EPA contacted the drinking water certification
authorities in the States of California, Maryland, and Pennsylvania.
These states were chosen based both on estimated radon occurrence and
the overall status of the programs. Ultimately, EPA collected
information on the availability and relative costs of radon analyses
for drinking water from a total of nine commercial laboratories.
Eight of the nine laboratories that were contacted do perform radon
analyses. All the laboratories were certified in one or more states to
perform radiochemical analyses. When asked what specific methods were
used, the laboratories responded with either the technique (liquid
scintillation counting) or a specific method citation. EPA Method 913
(which later was revised to become SM 7500-Rn) was cited by two of the
laboratories. EPA Method ``EERF Appendix B'' was cited by another
laboratory. The remaining laboratories indicated that they performed
liquid scintillation analyses and could accommodate requests for
methods employing that technique.
When asked about capacity, the laboratories indicated that they
each perform between 100 and 12,000 analyses per year. The latter
figure came from a laboratory that is currently involved in a large
ground water monitoring project in the western United States. The next
largest estimate was 300 samples per year. However, EPA expects that
like any other type of environmental analysis, given a regulatory
``driver'' to perform the analysis, and given the ability of LSC
analysis to be automated, the laboratory capacity will develop in a
timely manner.
EPA's 1992 Annual Report on Radiation Research and Methods
Validation reports the results of a collaborative study on radon
analysis (EPA 1993) and is another useful source of information
regarding potential radon laboratory capacity. This study employed 51
laboratories with the capability to perform liquid scintillation
analyses. This suggests that at that time there already existed a
substantial capacity for these analyses.
Further, the liquid scintillation apparatus is used for other
radiochemical analyses, including tritium. Information from EPA
regarding the performance evaluation program for tritium analyses
suggests that there are approximately 100-200 laboratories with the
necessary equipment. Much of the capacity for tritium analyses could
also be used for radon (EPA 1997). As of September 1997, 136 of 171
participating laboratories achieved acceptable results for tritium.
While the total number of participants and the number achieving
acceptable results vary between studies, the data indicate that there
is a substantial capability for liquid scintillation analysis
nationwide.
5. Laboratory Capacity: Laboratory Certification and Performance
Evaluation Studies
The availability of laboratories is also dependent on laboratory
certification efforts in the individual states with regulatory
authority for their drinking water programs. Until June of 1999, a
major component of many of these certification programs was their
continued participation in the current EPA Water Supply WS performance
evaluation (PE) program, which included radiochemistry PE studies. Due
to resource limitations, EPA has recently privatized EPA's PE programs,
including the Water Supply studies. EPA has addressed this topic in
public stakeholders meetings and in some recent publications, including
Federal Register notices and its June 1997 ``Labcert Bulletin'', which
can be downloaded from the Internet at ``http://www.epa.gov/OGWDW/
labcert3.html''. The decision to privatize the PE studies programs was
announced in the Federal Register on June 12, 1997 (62 FR 32112). This
notice indicated that in the future the National Institute of Standards
and Technology (NIST) would develop standards for private sector PT
sample providers and would evaluate and accredit these providers, while
the actual development and manufacture of PT samples would fall to the
private sector. Further information regarding the respective roles of
EPA and NIST in the privatized PT program can be downloaded from NIST's
homepage at ``http://ts.nist.gov/ts/htdocs/210/210.htm''. EPA believes
that this program will ensure the continued viability of the existing
PT programs, while maintaining government oversight.
This externalized proficiency testing program is in the process of
becoming operational. Under the externalized PT program:
EPA issues standards for the operation of the program,
NIST administers a program to accredit PT sample
providers,
Non-EPA PT sample providers develop and manufacture PT
sample materials and conduct PT studies,
Environmental laboratories purchase PT samples directly
from PT Sample Providers (approved by NIST or the State), and
Certifying authorities certify environmental laboratories
performing sample analyses in support of the various water programs
administered by the States and EPA under the Safe Drinking Water Act.
NIST is in the process of approving a provider for PT samples for
radionuclides, including radon. States also have the option of
approving their own PT sample providers. At this time, it is difficult
to speculate to what degree this externalization of the PT program will
affect short-term and long-term laboratory capacity for radon. EPA
recognizes that initial implementation problems may arise because of
the potential for near-term limited availability of radon PT samples.
EPA also recognizes that insufficient laboratory capacity may lead to a
short-term increase in analytical costs. In the absence of definitive
information regarding the future PT program, EPA solicits public
comment on this matter.
6. Efforts To Ensure a Uniform Proficiency Testing Program: NELAC
The National Environmental Laboratory Accreditation Conference
(NELAC) is also evaluating the issues surrounding privatization of the
SDWA PT program through its proficiency testing committee. NELAC serves
as a voluntary national standards-setting body for environmental
laboratory accreditation, and includes members from both state and
Federal regulatory and non-regulatory programs having environmental
laboratory oversight, certification, or accreditation functions. One of
the goals for the re-designed SDWA PT program is to be consistent with
NELAC's recommendations.
The members of NELAC meet bi-annually to develop consensus
standards through its committee structure. These consensus standards
are adopted by participants for use in their own programs in pursuit of
a uniform national laboratory accreditation program in which
environmental testing laboratories will be able to receive one annual
accreditation that is accepted nationwide. As part of its accreditation
program, NELAC is developing standards for a proficiency testing
program that addresses all fields of testing, including drinking water.
Recent meetings of the Proficiency Testing Committee of NELAC have
reviewed several important issues, including State selection of PT
sample providers and reciprocity between States.
[[Page 59299]]
These issues are described in more detail elsewhere (NELAC 1999a). The
NELAC Proficiency Testing Committee is currently drafting requirements
for radiochemical proficiency testing under SDWA. The June 15, 1999
draft (NELAC 1999b) of its radiochemical proficiency testing
requirements describes radiochemical PT sample designs, acceptance
limits, and other information.
The intent of the NELAC standards setting process is to ensure that
the needs of EPA and state regulatory programs are satisfied in the
context of a uniform national laboratory accreditation program. EPA
recognizes that cooperating with NELAC is an important part of the re-
design of the Proficiency Testing (PT) program for drinking water,
since NELAC provides a means for states, environmental testing
laboratories, and PT study providers to have direct input into the
process. It is hoped that this mutual effort will minimize the
potential disruption in the process of moving from the old EPA PE
program towards the new privatized PT program. EPA shares NELAC's goal
of encouraging uniformity in standards between primacy States regarding
laboratory proficiency testing and accreditation.
7. Laboratory Capacity: Holding Time
The short holding time for radon, 4 days in Method 7500-Rn,
presents concerns relative to the practical availability of laboratory
capacity as well. The 4-day holding time was also the focus of a number
of comments that EPA received in response to the 1991 proposed rule.
Many commenters were concerned that if a local laboratory is not
available, the only alternative will be to send the samples by
overnight delivery to a laboratory elsewhere. However, this situation
is not unique to the analysis of radon. As evidenced during the data
gathering pursuant to the Disinfection By-Products Information
Collection Rule (DBP ICR), several large commercial laboratories
already account for a sizable share of the market for SDWA analyses for
non-radon parameters, including organics, for which the holding times
are often 7 days. Given that a day would be required for shipping the
samples, only three days would remain for the laboratory to perform the
radon analysis (the day on which the sample is collected being ``day
zero''). Some commenters argued that for a large commercial laboratory
serving the water utilities, this short holding time will make it
difficult if not impossible to perform the necessary analyses within
the holding time. However, through common sense scheduling efforts
between the utility and the laboratory, such as not collecting samples
on Thursdays and Fridays, the holding time issue should be able to be
accommodated in light of the ability of the LSC method to be highly
automated.
D. Performance-Based Measurement System (PBMS)
On October 6, 1997, EPA published a Notice of the Agency's intent
to implement a Performance Based Measurement System (PBMS) in all of
its programs to the extent feasible (62 FR 52098). EPA is currently
determining how to adopt PBMS in its drinking water program, but has
not yet made final decisions. When PBMS is adopted in the drinking
water program, its intended purpose will be to increase flexibility in
laboratories in selecting suitable analytical methods for compliance
monitoring, significantly reducing the need for prior EPA approval of
drinking water analytical methods. Under PBMS, EPA will modify the
regulations that require exclusive use of Agency-approved methods for
compliance monitoring of regulated contaminants in drinking water
regulatory programs. EPA will probably specify ``performance
standards'' for methods, which the Agency would derive from the
existing approved methods and supporting documentation. A laboratory
would then be free to use any method or method variant for compliance
monitoring that performed acceptably according to these criteria. EPA
is currently evaluating which relevant performance characteristics
should be specified to ensure adequate data quality for drinking water
compliance purposes. After PBMS is implemented, EPA may continue to
approve and publish compliance methods for laboratories that choose not
to use PBMS. After EPA makes final determinations to implement PBMS in
programs under the Safe Drinking Water Act, EPA would then provide
specific instruction on the specified performance criteria and how
these criteria would be used by laboratories for radon compliance
monitoring.
E. Proposed Monitoring and Compliance Requirements for Radon
1. Background
The monitoring regulation for radon proposed in 1991 by EPA
required that groundwater systems monitor for radon at each entry point
to the distribution system quarterly for one year initially. Monitoring
could be reduced to one sample annually per entry point to the
distribution system if the average of all first quarterly samples was
below the MCL. States could allow systems to reduce monitoring to once
every three years if the system demonstrated that results of all
previous samples collected were below the MCL. The proposal also
allowed States to grant waivers to groundwater systems to reduce the
frequency of monitoring, up to once every 9 years, if States determined
that radon levels in drinking water were consistently and reliably
below the MCL. Comments made in response to the proposed monitoring
requirements for radon were mainly concerned that the proposed
monitoring requirements including number of samples and the frequency
of monitoring did not adequately take into account the effect of
seasonal variations in radon levels on determining compliance. Other
commenters felt that sampling at the entry point of the distribution
system was not representative of exposure to radon, and they suggested
that sampling for radon should be done at the point of use.
Since the 1991 proposal EPA has obtained additional information
from States, the waterworks industry and academia on the occurrence of
radon, including data on the temporal variability of radon. Utilizing
this additional data, the Agency performed extensive statistical
analyses to predict how temporal, analytical variations and variations
between individual wells may affect exposure to radon. The results of
these analyses are described in detail in the report ``Methods,
Occurrence and Monitoring Document for Radon'' in the docket for this
rule (USEPA 1999g). As a result of the new information available, EPA
was able to refine the requirements for monitoring and address the
concerns expressed by the commenters on the 1991 proposal.
The proposed monitoring requirements for radon are consistent with
the monitoring requirements for regulated drinking water contaminants,
as described in the Standardized Monitoring Framework (SMF) promulgated
by EPA under the Phase II Rule of the National Primary Drinking Water
Regulations (NPDWR) and revised under Phases IIB and V. The goal of the
SMF is to streamline the drinking water monitoring requirements by
standardizing them within contaminant groups and by synchronizing
monitoring schedules across contaminant groups. A summary of monitoring
requirements in this proposal, the SMF and the 1991 proposal are
provided in Table VIII.E.1.
[[Page 59300]]
Table VIII.E.1.--Comparison of Monitoring Requirements
------------------------------------------------------------------------
Monitoring requirements for radon
-------------------------------------------------------------------------
1999 Proposal--MCL/ SMF for IOCs in
1991 Proposal AMCL groundwater
------------------------------------------------------------------------
Initial Monitoring Requirements
------------------------------------------------------------------------
Four consecutive quarters of Four consecutive Four consecutive
monitoring at each entry point quarters of quarters of
for one year. Initial monitoring at monitoring at
monitoring was proposed to have each entry point. each entry point
been completed by January 1, Initial for sampling
1999. monitoring must points initially
begin by three exceeding MCL.
years from date
of publication of
the final rule in
Federal Register
of 4.5 years from
date of
publication of
the final rule in
Federal Register
(depending on
effective date
applicable to the
State).
------------------------------------------------------------------------
Routine Monitoring Requirements
------------------------------------------------------------------------
One sample annually if average One sample One sample at each
from four consecutive quarterly annually if sample point
samples taken initially is less average from four during the
than MCL. consecutive initial 3 year
quarterly samples compliance period
is less than MCL/ for groundwater
AMCL, and at the systems for
discretion of sampling points
State. below MCL.
------------------------------------------------------------------------
1991 Proposal 1999 Proposal--MCL SMF for IOCs in
Groundwater
------------------------------------------------------------------------
Reduced Monitoring Requirements
------------------------------------------------------------------------
State may allow groundwater State may allow State may allow
systems to reduce the frequency CWS using groundwater
of monitoring to once every groundwater to systems to reduce
three years provided that they reduce monitoring monitoring
have monitored quarterly in the frequency to:. frequency to:
initial year and completed Once every three Once every three
annual testing in the second years if average years if samples
and third year of the first from four subsequently
compliance period. Groundwater consecutive detects less than
systems must demonstrate that quarterly samples MCL and
all previous analytical samples is less than \1/ determined by
were less than the MCL. 2\ the MCL/AMCL, State to be
provided no ``reliably and
samples exceed consistently
the MCL/AMCL. and below MCL.''
if the system is
determined by
State to be
``reliably and
consistently
below MCL/AMCL ''.
------------------------------------------------------------------------
Monitoring Requirements for Radon
------------------------------------------------------------------------
1991 Proposal 1999 Proposal--MCL/ SMF for IOCs in
AMCL Groundwater
------------------------------------------------------------------------
Increased Monitoring Requirements
------------------------------------------------------------------------
Systems monitoring annually or Systems monitoring If the MCL is
once per three year compliance annually would be exceeded in a
period exceed the radon MCL in required to single sample,
a single sample would be increase the system
required to revert to quarterly monitoring if the required to begin
monitoring until the average of MCL/AMCL for sampling
4 consecutive samples is less radon is exceeded quarterly until
than the MCL. Groundwater in a single State determines
systems with unconnected wells sample, the that it is
would be required to conduct system would be ``reliably and
increased monitoring only at required to consistently''
those wells exceeding the MCL. revert to below MCL.
The State may require more quarterly
frequent monitoring than monitoring until
specified. the average of 4
Systems may apply to the State consecutive
to conduct more frequent samples is less
monitoring than the minimum than the MCL/AMCL.
monitoring frequencies Systems monitoring
specified. once every three
years would be
required to
monitor annually
if the radon
level is less
than MCL/AMCL but
above \1/2\ MCL/
AMCL in a single
sample. Systems
may revert to
monitoring once
per three years
if the average of
the initial and
three consecutive
annual samples is
lees than \1/2\
MCL/AMCL.
CWS using
groundwater with
un-connected
wells would be
required to
conduct increased
monitoring only
at those well
which are
affected.
------------------------------------------------------------------------
[[Page 59301]]
Monitoring Requirements for Radon
------------------------------------------------------------------------
1991 Proposal 1999 Proposal--MCL SMF for IOCs in
Groundwater
------------------------------------------------------------------------
Confirmation Samples
------------------------------------------------------------------------
Where the results of sampling Systems may Where the results
indicate an exceedence of the collect sampling indicate
maximum contaminant level, the confirmation an exceedence of
State may require that one samples as the maximum
additional sample be collected specified by the contaminant
as soon as possible after the State. The level, the State
initial sample was taken [but average of the may require that
not to exceed two weeks] at the initial sample one additional
same sampling point. The and any sample be
results of the of the initial confirmation collected as soon
sample and the confirmation samples will be as possible after
sample shall be averaged and used to determine the initial
the resulting average shall be compliance. sample was taken
used to determine compliance. [but not to
exceed two weeks]
at the same
sampling point.
The results of
the initial
sample and the
confirmation
sample shall be
averaged and the
resulting average
shall be used to
determine
compliance.
------------------------------------------------------------------------
Grandfathering of Data
------------------------------------------------------------------------
If monitoring data collected If monitoring data States may allow
after January 1, 1985 are collected after previous sampling
generally consistent with the proposal of the data to satisfy
requirements specified in the rule are the initial
regulation, than the State may consistent with sampling
allow the systems to use those the requirements requirements
data to satisfy the monitoring specified in the provided the data
requirements for the initial regulation, then were collected
compliance period. the State may after January 1,
allow the systems 1990.
to use those data
to satisfy the
monitoring
requirements for
the initial
compliance period.
------------------------------------------------------------------------
Monitoring Requirements for Radon
------------------------------------------------------------------------
1991 Proposal 1999 Proposal--MCL SMF for IOCs in
Groundwater
------------------------------------------------------------------------
Waivers
------------------------------------------------------------------------
State may grant waiver to The State may The State may
groundwater systems to reduce grant a grant waiver to
the frequency of monitoring, up monitoring waiver groundwater
to nine years. If State to systems to systems after
determines that radon levels in reduce the conducting
drinking water are ``reliably frequency of vulnerability
and consistently'' below the monitoring to up assessment to
MCL. to one sample reduce the
every nine years frequency of
based on previous monitoring, up to
analytical nine years, if
results, State determines
geological that radon levels
characteristics in drinking water
of source water are ``reliably
aquifer and if a and
State determines consistently''
that radon levels below the MCL.
in drinking water System must have
are ``reliably three previous
and samples.
consistently'' Analytical
below the MCL/ results of all
AMCL. previous samples
Analytical results taken must be
of all previous below MCL.
samples taken
must be below \1/
2\ the MCL/AMCL.
------------------------------------------------------------------------
In developing the proposed compliance monitoring requirements for
radon, EPA considered:
(1) The likely source of contamination in drinking water;
(2) The differences between ground water and surface water systems;
(3) The collection of samples which are representative of consumer
exposure;
(4) Sample collection and analytical methods;
(5) The use of appropriate historical data to identify vulnerable
systems and to specify monitoring requirements for individual systems;
(6) The analytical, temporal and intra-system variance of radon
levels;
(7) The use of appropriate historical data and statistical analysis
to establish reduced monitoring requirements for individual systems;
and
(8) The need to provide flexibility to the States to tailor
monitoring requirements to site-specific conditions by allowing them
to:
--Grant waivers to systems to reduce monitoring frequency, provided
certain conditions are met.
--Require confirmation samples for any sample exceeding the MCL/AMCL.
--Allow the use of previous sampling data to satisfy initial sampling
requirements.
--Increase monitoring frequency.
--Decrease monitoring frequency.
2. Monitoring for Surface Water Systems
CWSs relying exclusively on surface water as their water source
will not be required to sample for radon. Systems that rely in part on
ground water would be considered groundwater systems for purposes of
radon monitoring. Systems that use ground water to supplement surface
water during low-flow periods will be required to monitor for radon.
Ground water under the influence of surface water would be considered
ground water for this regulation.
3. Sampling, Monitoring Schedule and Initial Compliance for CWS Using
Groundwater
EPA is retaining the quarterly monitoring requirement for radon as
proposed initially in the 1991 proposal to account for variations such
as sampling, analytical and temporal variability in radon levels.
Results of analysis of data obtained since 1991, estimating
contributions of individual sources of variability to overall variance
in the radon data sets evaluated, indicated that sampling and
analytical variance contributes less than 1 percent to the overall
variance. Temporal variability within single wells accounts
[[Page 59302]]
for between 13 and 18 percent of the variance in the data sets
evaluated, and a similar proportion (12-17 percent) accounts for
variation in radon levels among wells within systems. (USEPA 1999g)
The Agency performed additional analyses to determine whether the
requirement of initial quarterly monitoring for radon was adequate to
account for seasonal variations in radon levels and to identify non-
compliance with the MCL/AMCL. Results of analysis based on radon levels
modeled for radon distribution for ground water sources (USEPA 1999g)
and systems (USEPA 1998a) in the U.S. show that the average of the
first four quarterly samples provides a good indication of the
probability that the long-term average radon level in a given source
would exceed an MCL or AMCL. Tables VIII.E.2 and VIII.E.3 show the
probability of the long-term average radon level exceeding the MCL and
AMCL at various averages obtained from the first four quarterly samples
from a source.
Table VIII.E.2.--The Relationship Between the First-Year Average Radon
Level and the Probability of the Long-Term Radon Average Radon Levels
Exceeding the MCL
------------------------------------------------------------------------
Then the probability that the
If the average of the first four long-term average radon level
quarterly samples from a source is in that source exceeds 300 pCi/
L is
------------------------------------------------------------------------
Less than 50 pCi/L..................... 0 percent.
Between 50 and 100 pCi/L............... 0.5 percent.
Between 100 and 150 pCi/L.............. 0.4 percent.
Between 150 and 200 pCi/L.............. 7.2 percent.
Between 200 and 300 pCi/L.............. 26.8 percent.
------------------------------------------------------------------------
Table VIII.E.3.--The Relationship Between the First-Year Average Radon
Level and the Probability of the Long-Term Radon Average Radon Levels
Exceeding the AMCL
------------------------------------------------------------------------
Then the probability that the
If the average of the first four long-term average radon level
quarterly samples from a source is in that source exceeds 4000 pCi/
L is
------------------------------------------------------------------------
Less than 2,000 pCi/L.................. Less than 0.1 percent.
Between 2,000 and 2,500 pCi/L.......... 9.9 percent.
Between 2,500 and 3,000 pCi/L.......... 15.1 percent.
Between 3,000 and 4,000 pCi/L.......... 32.9 percent.
------------------------------------------------------------------------
The Agency proposes that systems relying wholly or in part on
ground water will be required to initially sample quarterly for radon
for one year at each well or entry point to the distribution system.
All samples will be required to be of finished water, as it enters the
distribution system after any treatment and storage. If the average of
the four quarterly samples at each well is below the MCL/AMCL,
monitoring may be reduced to once a year at State discretion. Systems
may be required to continue monitoring quarterly in instances where the
average of the quarterly samples at each well is below but close to the
MCL/AMCL. The reason for this is that in such cases, there is a good
chance for the long-term average radon level to exceed the MCL/AMCL.
Systems already on-line must begin initial monitoring for
compliance with the MCL/AMCL by the compliance dates specified in the
rule (i.e., 3 years after the date of promulgation or 4.5 years after
the date of promulgation). Monitoring requirements for new sources will
be determined by the State. The compliance dates are discussed in
detail in Section VII.E, Compliance Dates.
The Agency is retaining the requirement as proposed in 1991 to
sample at the entry point to the distribution system. Sampling at the
entry point allows the system to account for radon decay during storage
and removal during the treatment process. The reason for not allowing
sampling at the point of use is that this approach would not take into
account higher exposure levels that may be encountered at locations
upstream from the sampling site. In addition, sampling at the entry
point will make it easier to identify and isolate possible contaminant
sources within the system. The sample collection sites at each entry
point to the distribution system and the monitoring schedule requiring
sampling for four consecutive quarters proposed herein is consistent
with the SMF. This approach streamlines monitoring since the same
sampling points can be used for the collection of samples for other
source-related contaminants.
EPA specifically requests comments on the following aspects of the
proposed monitoring requirements:
The appropriateness of the proposed initial monitoring
period.
The availability and capabilities of laboratories to
analyze radon samples collected during the initial compliance period.
The Agency recognizes that short-term implementation problems may arise
to meet the initial monitoring deadline because of the potential
limited availability of radon performance evaluation (PE) samples used
to evaluate and certify laboratories.
The appropriateness of the proposed number and frequency
of samples required to monitor for radon.
The designation of sampling locations at the entry point
to the distribution system which is located after any treatment and
storage. Comments are also solicited on the definition of sampling
points that are representative of consumer exposure.
Designating sampling locations and frequencies that permit
simultaneous monitoring for all regulated contaminants, whenever
possible and advantageous. The proposed sampling locations would be
such that the same sampling locations could be used for the collection
of samples for other source-related contaminants such as the volatile
organic chemicals and inorganic chemicals, which would simplify sample
collection efforts.
EPA also solicits comments on whether the monitoring requirements
should include additional monitoring for radon as a source of consumer
exposure from the distribution system. Results of investigations in
Iowa indicate that in some instances, pipe scale deposited in the
distribution system can be a source of exposure to radon. Community
ground water systems could be required to collect an additional sample
from the distribution system during the initial year of monitoring, at
the same time the entry point sample is collected, and continue to
collect samples from the distribution system annually if it is shown
that exceedence of the MCL/AMCL is caused by the release of radon from
deposited scale in the interior of the distribution system. Results
obtained from distribution samples could provide information on the
extent and frequency
[[Page 59303]]
of occurrence of radon originating from distribution systems.
4. Increased/Decreased Monitoring Requirements
Initial compliance with the MCL/AMCL will be determined based on an
average of four quarterly samples taken at individual sampling points
in the initial year of monitoring. Systems with averages exceeding the
MCL/AMCL at any sampling point will be deemed to be out of compliance.
Systems in a non-MMM State exceeding the MCL will have the option to
develop and implement a local MMM program in accordance with the
timeframe discussed in Section VII.E, Compliance Dates without
receiving a MCL violation.
Systems exceeding the MCL/AMCL will be required to monitor
quarterly until the average of four consecutive samples is less than
the MCL/AMCL. Systems will then be allowed to collect one sample
annually if the average from four consecutive quarterly samples is less
than the MCL/AMCL and if the State determines that the system is
reliably and consistently below the MCL/AMCL.
Systems will be allowed to reduce monitoring frequency to once
every three years (one sample per compliance period) per well or
sampling point, if the average from four consecutive quarterly samples
is less than \1/2\ the MCL/AMCL and the State determines that the
system is reliably and consistently below the MCL/AMCL. As shown in
Tables VIII.E.2 and VIII.E.3, EPA believes that there is sufficient
margin of safety to allow for this since there is a small probability
that long term average radon levels will exceed the MCL/AMCL.
Systems monitoring annually that exceed the radon MCL/AMCL in a
single sample will be required to revert to quarterly monitoring until
the average of four consecutive samples is less than the MCL/AMCL.
Community ground water systems with unconnected wells will be required
to conduct increased monitoring only at those wells exceeding the MCL/
AMCL. Compliance will be based on the average of the initial sample and
three consecutive quarterly samples.
Systems monitoring once per compliance period or less frequently
which exceed \1/2\ the MCL/AMCL (but do not exceed the MCL/AMCL) in a
single sample would be required to revert to annual monitoring. Systems
may revert to monitoring once every three years if the average of the
initial and three consecutive annual samples is less than \1/2\ the
MCL/AMCL. Community ground water systems with unconnected wells will be
required to conduct increased monitoring only at those wells exceeding
the MCL/AMCL.
States may grant a monitoring waiver reducing monitoring frequency
to once every nine years (once per compliance cycle) provided the
system demonstrates that it is unlikely that radon levels in drinking
water will occur above the MCL/AMCL. In granting the monitoring waiver,
the State must take into consideration factors such as the geological
area where the water source is located, and previous analytical results
which demonstrate that radon levels do not occur above the MCL/AMCL.
The monitoring waiver will be granted for up to a nine year period.
(Given that all previous samples are less than \1/2\ the MCL/AMCL, then
it is highly unlikely that the long-term average radon levels would
exceed the MCL/AMCL.)
If the analytical results from any sampling point are found to
exceed the MCL/AMCL (in the case of routine monitoring) or \1/2\ the
MCL/AMCL (in the case of reduced monitoring), the State may require the
system to collect a confirmation sample(s). The results of the initial
sample and the confirmation sample(s) shall be averaged and the
resulting average shall be used to determine compliance.
EPA specifically requests comments on the following aspects of the
proposed monitoring requirements :
Allowing systems at State discretion, to reduce monitoring
frequencies as long as the system demonstrates that its radon levels
are maintained below the MCL/AMCL. For example, all community ground
water systems would be required to collect one sample from each entry
point to the distribution system (located after any treatment and
storage) quarterly at first and annually after compliance is
established. MCL/AMCL exceedence would trigger reverting to quarterly
sampling until compliance with the MCL/AMCL is reestablished.
Compliance is reestablished when the average of four consecutive
quarterly samples is below the MCL/AMCL.
Allowing States to reduce monitoring requirements to not
less than once every three years if the average radon levels from four
consecutive quarterly samples is less than \1/2\ the MCL/AMCL, and the
State determines that the radon levels in the drinking water are
reliably and consistently below \1/2\ the MCL/AMCL. A single sample
exceeding \1/2\ the MCL/AMCL would trigger reverting to sampling
annually. Comments are solicited on the criteria allowing the utility
to revert to monitoring once every three years if the average of the
initial and three consecutive annual samples is less than \1/2\ the
MCL/AMCL.
Factors affecting State discretion to grant waivers. In
addition, the Agency solicits comments on the advisability of reducing
the monitoring frequency up to nine years between samples. Comments are
solicited on the requirement that all previous samples (that might be
used to identify systems which are very unlikely to exceed the MCL/
AMCL) must be below \1/2\ the MCL/AMCL in order for a system to qualify
for a waiver.
Allowing States to require the collection of confirmation
samples to verify initial sample results as specified by the State, and
to use the average of the initial sample and the confirmation samples
to determine compliance.
5. Grandfathering of Data
At a State's discretion, sampling data collected since the proposal
could be used to satisfy the initial sampling requirements for radon,
provided that the system has conducted a monitoring program and used
analytical methods that meet proposal requirements. The Agency wants to
provide water suppliers with the opportunity to synchronize their radon
monitoring program with monitoring for other contaminants and to get an
early start on their monitoring program if they wish to do so.
The Agency solicits comments on the advisability of allowing the
use of monitoring data obtained since the proposal to satisfy the
initial monitoring requirements.
IX. State Implementation
This section describes the regulations and other procedures and
policies States have to adopt, or have in place, to implement today's
proposed rule. States must continue to meet all other conditions of
primacy in 40 CFR part 142.
Section 1413 of the SDWA establishes requirements that a State must
meet to obtain or maintain primacy enforcement responsibility (primacy)
for its public water systems. These include: (1) Adopting drinking
water regulations that are no less stringent than Federal NPDWRs in
effect under Section 1412(b) of the Act; (2) adopting and implementing
adequate procedures for enforcement; (3) keeping records and making
reports available on activities that EPA requires by regulation; (4)
issuing variances and exemptions (if allowed by the State) under
conditions no less stringent than allowed by Sections 1415 and 1416;
(5) adopting
[[Page 59304]]
and being capable of implementing an adequate plan for the provision of
safe drinking water under emergency situations; and (6) adopting
authority for administrative penalties.
40 CFR part 142 sets out the specific program implementation
requirements for States to obtain primacy for the public water supply
supervision (PWSS) program, as authorized under SDWA 1413 of the Act.
In addition to meeting the basic primacy requirements, States may be
required to adopt special primacy provisions pertaining to a specific
regulation. States are required by 40 CFR 142.12 to include these
regulation-specific provisions in an application for approval of their
program revisions. To maintain primacy for the PWS program and to be
eligible for interim primacy enforcement authority for future
regulations, States must adopt today's rule, when final, along with the
special primacy requirements discussed next. Interim primacy
enforcement authority allows States to implement and enforce drinking
water regulations once State regulations are effective and the State
has submitted a complete and final primacy revision application. Under
interim primacy enforcement authority, States are effectively
considered to have primacy during the period that EPA is reviewing
their primacy revision application.
A. Special State Primacy Requirements
In addition to adopting drinking water regulations at least as
stringent as the regulations described in the previous sections, EPA
requires that States adopt certain additional provisions related to
this regulation, in order to have their drinking water program revision
application approved by EPA. States have two options when implementing
this rule. States may adopt the AMCL and implement a State-wide MMM
program plan or States may adopt the MCL. If a State chooses to adopt
the MCL, CWSs in that State have the option to develop and implement a
State-approved local MMM program plan and comply with the AMCL.
To ensure that the State program includes all the elements
necessary for a complete enforcement program, EPA is proposing that 40
CFR part 142 be amended to require the following in order to obtain
primacy for this rule:
(1) Adoption of the promulgated Radon Rule, and
(2) One of the following, depending on which regulatory option the
State chooses to adopt:
(a) If a State chooses to develop and implement a State-wide MMM
program plan and adopt the AMCL, the primacy application must contain a
copy of the State-wide MMM program plan meeting the four criteria in 40
CFR Part 141 Subpart R and the following: a description of how the
State will make resources available for implementation of the State-
wide MMM program plan, and a description of the extent and nature of
coordination between interagency programs (i.e., indoor radon and
drinking water programs) on development and implementation of the MMM
program plan, including the level of resources that will be made
available for implementation and coordination between interagency
programs (i.e., indoor air and drinking water programs).
(b) If a State chooses to adopt the MCL, the primacy application
must contain a description of how the State will implement a program to
approve local CWS MMM program plans prepared to meet the criteria
outlined in 40 CFR Part 141 Subpart R. In addition, the primacy
application must contain a description of how the State will ensure
local CWS MMM program plans are implemented and the extent and nature
of coordination between interagency programs (i.e., indoor radon and
drinking water programs) on development and implementation of the MMM
program, including the level of resources that will be made available
for implementation and coordination between interagency programs (i.e.,
indoor air and drinking water programs), as well as, a description of
the reporting and record keeping requirements for the CWSs.
States are required to submit their primacy revision application
packages by two years from the date of publication of the final rule in
the Federal Register. For States adopting the AMCL, EPA approval of a
State's primacy revision application is contingent on submission of and
EPA approval of the State's MMM program plan. Therefore, EPA is
proposing to require submission of State-wide MMM program plans as part
of the complete and final primacy revision application. This will
enable EPA to review and approve the complete primacy application in a
timely and efficient manner in order to provide States with as much
time as possible to begin to implement MMM programs. In accordance with
Section 1413(b)(1) of SDWA and 40 CFR 142.12(d)(3), EPA is to review
primacy applications within 90 days. Therefore, although the SDWA
allows 180 days for EPA review and approval of MMM program plans, EPA
expects to review and approve State primacy revision applications for
the AMCL, including the State-wide MMM program plan, within 90 days of
submission to EPA.
EPA is proposing that States notify CWSs of their decision to adopt
the MCL or AMCL at the time they submit their primacy application
package to EPA (24 months after publication of the final rule). If a
State adopts the MCL, CWSs choosing to implement a local CWS MMM
program and comply with the AMCL will be required to have completed
initial monitoring, notify the State of their intention, and begin
developing a plan 4 years after the rule is final. EPA is particularly
concerned that these CWSs have sufficient time to develop MMM program
plans with local input and allow for State approval. Therefore, it is
EPA's expectation that States will be submitting complete and final
primacy revision applications by 24 months from the date of publication
of the final rule in Federal Register. In reviewing any State requests
for extensions of time in submitting primacy revision applications, EPA
will consider whether sufficient time will be provided to CWSs to
develop and get State approval of their local MMM program plans prior
to implementation.
B. State Record Keeping Requirements
Today's rule does not include changes to the existing recordkeeping
provisions required by 40 CFR 142.14. MMM record keeping requirements
will be addressed in each State's primacy revision application
submission to meet the special primacy requirements for radon (40 CFR
142.16).
C. State Reporting Requirements
Currently States must report to EPA information under 40 CFR 142.15
regarding violations, variances and exemptions, enforcement actions and
general operations of State public water supply programs.
In accordance with the Safe Drinking Water Act (SDWA), EPA is to
review State MMM programs at least every five years. For the purposes
of this review, the States with EPA-approved MMM program plans shall
provide written reports to EPA in the second and fourth years between
initial implementation of the MMM program and the first 5-year review
period, and in the second and fourth years of every subsequent 5-year
review period. EPA will review these programs to determine whether they
continue to be expected to achieve risk reduction of indoor radon using
the information provided in the two biennial reports. EPA requests
comment on this approach. These reports are required to include the
following information:
[[Page 59305]]
A quantitative assessment of progress towards meeting the
required goals described in Section VI. A., including the number or
rate of existing homes mitigated and the number or rate of new homes
built radon-resistant since implementation of the States' MMM program:
and
A description of accomplishments and activities that
implement the program strategies outlined in the implementation plan
and in the two required areas of promoting increased testing and
mitigation of existing homes and promoting increased use of radon-
resistant techniques in construction of new homes.
If goals were defined as rates, the State must also
provide an estimate of the number of mitigations and radon-resistant
new homes represented by the reported rate increase for the two-year
period.
If the MMM program plan includes goals for promoting
public awareness of the health effects of indoor radon, testing of
homes by the public; testing and mitigation of existing schools; and
construction of new public schools to be radon-resistant, the report is
also required to include information on results and accomplishments in
these areas.
EPA will use this information in discussions and consultations with
the State during the five-year review to evaluate program progress and
to consider what modifications or adjustments in approach may be
needed. EPA envisions this review process will be one of consultation
and collaboration between EPA and the States to evaluate the success of
the program in achieving the radon risk reduction goals outlined in the
approved programs. If EPA determines that a MMM program in not
achieving progress towards its goals, EPA and the State shall
collaborate to develop modifications and adjustments to the program to
be implemented over the five year period following the review. EPA will
prepare a summary of the outcome of the program evaluation and the
proposed modification and adjustments, if any, to be made by the State.
States that submit a letter to the Administrator by 90 days after
publication of the final rule committing to develop an MMM program
plan, must submit their first 2-year report by 6.5 years from
publication of the final rule. For States not submitting the 90-day
letter, but choosing subsequently to submit an MMM program plan and
adopt the AMCL, the first 2-year report must be submitted to EPA by 5
years from publication of the final rule. States shall make available
to the public each of these two-year reports, as well as the EPA
summaries of the five-year reviews of a State's MMM program, within 90
days of completion of the reports and the review.
In primacy States without a State-wide MMM program, the States
shall provide a report to EPA every five-years on the status and
progress of CWS MMM programs towards meeting their goals. The first of
such reports would be due 5 years after CWSs begin implementing a local
MMM program which is 5.5 years from publication of the final rule.
D. Variances and Exemptions
Section 1415 of the SDWA authorizes the State to issue variances
from NPDWRs (the term ``State'' is used in this preamble to mean the
State agency with primary enforcement responsibility, or ``primacy,''
for the public water supply system program or EPA if the State does not
have primacy). The State may issue a variance under Section 1415(a) if
it determines that a system cannot comply with an MCL due to the
characteristics of its source water, and on condition that the system
install BAT. Under Section 1415(a), EPA must propose and promulgate its
finding identifying the best available technology, treatment
techniques, or other means available for each contaminant, for purposes
of Section 1415 variances, at the same time that it proposes and
promulgates a maximum contaminant level for such contaminant. EPA's
finding of BAT, treatment techniques, or other means for purposes of
issuing variances may vary, depending upon the number of persons served
by the system or for other physical conditions related to engineering
feasibility and costs of complying with MCLs, as considered appropriate
by the EPA. The State may not issue a variance to a system until it
determines among other things that the variance would not pose an
unreasonable risk to health (URTH). EPA has developed draft guidance,
``Guidance in Developing Health Criteria for Determining Unreasonable
Risks to Health'' (USEPA 1990) to assist States in determining when an
unreasonable risk to health exists. EPA expects to issue final guidance
for determining when URTH levels exist later this year. When a State
grants a variance, it must at the same time prescribe a schedule for
(1) compliance with the NPDWR and (2) implementation of such additional
control measures as the State may require.
Under Section 1416(a), the State may exempt a public water system
from any MCL and/or treatment technique requirement if it finds that
(1) due to compelling factors (which may include economic factors), the
system is unable to comply or develop an alternative supply, (2) the
system was in operation on the effective date of the MCL or treatment
technique requirement, or, for a newer system, that no reasonable
alternative source of drinking water is available to that system, (3)
the exemption will not result in an unreasonable risk to health, and
(4) management or restructuring changes cannot be made that would
result in compliance with this rule. Under Section 1416(b), at the same
time it grants an exemption the State is to prescribe a compliance
schedule and a schedule for implementation of any required interim
control measures. The final date for compliance may not exceed three
years after the NPDWR effective date except that the exemption can be
renewed for small systems for limited time periods.
EPA will not list ``small systems variance technologies'', as
provided in Section 1415(e)(3) of the Act, since EPA has determined
that affordable treatment technologies exist for all applicable system
sizes and water quality conditions. As stated in this Section of the
Act, if the Administrator finds that small systems can afford to comply
through treatment, alternate water source, restructuring, or
consolidation, according to the affordability criteria established by
the Administrator, then systems are not eligible for small systems
variances. Small systems will, however, still be able to apply for
``regular'' variances and exemptions, pursuant to Sections 1415 and
1416 of the Act.
E. Withdrawing Approval of a State MMM Program
If EPA determines that a State MMM program is not achieving
progress towards its MMM goals, and the State repeatedly fails to
correct, modify and adjust implementation of its MMM program after
notice by EPA, EPA may withdraw approval of the State's MMM program
plan. The State will be responsible for notifying CWSs of the
Administrator's withdrawal of approval of the State-wide MMM program
plan. The CWSs in the State would then be required to comply with the
MCL within one year from date of notification, or develop a State-
approved CWS MMM program plan. EPA will work with the State to develop
a State process for review and approval of CWS MMM program plans that
meet
[[Page 59306]]
the required criteria and establish a time frame for submittal of
program plans by CWSs that choose to continue complying with the AMCL.
The review process will allow for local public participation in
development and review of the program plan.
X. What Do I Need To Tell My Customers? Public Information
Requirements
A. Public Notification
Sections 1414(c)(1) and (c)(2) of the SDWA, as amended, require
that public water systems notify persons served when violations of
drinking water standards occur. EPA recently proposed to revise the
current public notification regulations to incorporate new statutory
provisions enacted under the 1996 SDWA amendments (64 FR 25963, May 13,
1999). The purpose of public notification is to alert customers in a
timely manner to potential risks from violations of drinking water
standards and the steps they should take to avoid or minimize such
risks.
Today's regulatory action would add violation of the radon NPDWR to
the list of violations requiring public notice under the May 13, 1999,
proposed public notification rule. Today's action would make three
changes to the proposed public notification rule.
First, Appendix A to Subpart Q would be modified to
require a Tier 2 public notice for violations of the MCL and AMCL for
all community water systems. Under the proposed rule, Tier 2 public
notices would be required for violations and situations with potential
to have serious adverse effects on human health. Tier 2 public notices
must be distributed within 30 days after the violation is known, and
must be repeated every three months until the violation is resolved.
Second, Appendix A would also be modified to require a
Tier 3 public notice for all radon monitoring and testing procedure
violations and for violations of the Multimedia Mitigation (MMM)
Program Plan. Tier 3 public notices must be distributed within a year
of the violation and could, at the water system's option, be included
in the annual Consumer Confidence Report (CCR).
Third, Appendix B to Subpart Q would be modified to add
standard health effects language, which public water systems are
required to use in their notices when violations of the AMCL or MMM
occur. EPA proposes that the standard health effects language for these
violations, to be included in CCR annual reports and public notices.
The language for violation of the (A)MCL would be as follows: ``People
who use drinking water containing radon in excess of the (A)MCL for
many years may have an increased risk of getting lung and stomach
cancer.'' The language for violation of the MMM would be as follows:
``Your water system is not complying with requirements to promote the
reduction of lung cancer risks from radon in indoor air, which is a
problem in some homes. Radon is a naturally occurring radioactive gas
which may enter homes from the surrounding soil and may also be present
in drinking water. Because your system is not complying with applicable
requirements, it may be required to install water treatment technology
to meet more stringent standards for radon in drinking water. The best
way to reduce radon risk is to test your home's indoor air and, if
elevated levels are found, hire a qualified contractor to fix the
problem. For more information, call the National Safety Council's Radon
Hotline at 1-800-SOS-RADON.'' The standard health effects language
public water systems are to use in their public notice would be
identical to that used in the annual CCR.
The final public notification rule is expected to be published
around December, 1999, well in advance of the August, 2000, deadline
for the final radon regulation. The final public notification
requirements for radon, therefore, will be published with the final
radon rule. The Agency will republish the tables in Appendices A and B
to Subpart Q of Part 141 with all necessary changes in the final rule.
B. Consumer Confidence Report
Section 1414(d) of the SDWA requires that all community water
systems provide annual water quality reports (or consumer confidence
reports (CCRs)) to their customers. In their reports, systems must
provide, among other things, the levels and sources of all detected
contaminants, the potential health effects of any contaminant found at
levels that violate EPA or State rules, and short educational
statements on contaminants of particular interest.
Today's action updates the standard CCR rule requirements in
subpart O and adds special requirements that reflect the multimedia
approach of this rule. The intent of these provisions is to assist in
clearer communication of the relative risks of radon in indoor air from
soil and from drinking water, and to encourage public participation in
the development of the State or CWS MMM program plans. Systems that
detect radon at a level that violates the A/MCL would have to include
in their report a clear and understandable explanation of the violation
including: the length of the violation, actions taken by the system to
address the violation, and the potential health effects (using the
language proposed today for Appendix C to subpart O: ``People who use
drinking water containing radon in excess of the (A)MCL for many years
may have an increased risk of getting lung and stomach cancer''). This
approach is comparable to that used for other drinking water
contaminants.
In addition, recognizing the novelty of the MMM approach and the
interest that consumers may have in participating in the design of the
MMM program, today's action also proposes that any system that has
ground water as a source must include information in its report in the
years between publication of the final rule and the date by which
States, or systems, will be required to implement an MMM program. This
information would include a brief educational statement on radon risks,
explaining that the principal radon risk comes from radon in indoor
air, rather than drinking water, and for that reason, radon risk
reduction efforts may be focused on indoor air rather than drinking
water. This information will also note that many States and systems are
in the process of creating programs to reduce exposure to radon, and
encourage readers to call the Radon Hotline (800-SOS-RADON) or visit
EPA's radon web site (www.epa.gov/iaq/radon) for more information. A
system would be able to use language provided in the proposed rule by
EPA or could chose to tailor the wording to its specific local
circumstances in consultation with the primacy agency. EPA recognizes
that this creates a slight additional burden on community water system
operators, but believes that the value of strong public support for,
and participation in, the creation of the MMM program outweighs this
burden. EPA also recognizes that this notice may provoke some
confusion, since CCRs would alert consumers to the risks presented by a
contaminant which most systems have never monitored in their water,
although the notice would state that the system would be testing and
would provide customers with the results. EPA is requesting comment on
this proposed notice.
Finally, the Agency will republish the tables in Appendices A, B,
and C to Subpart O of Part 141 with all necessary changes in the final
rule.
[[Page 59307]]
Risk Assessment and Occurrence
XI. What Is EPA's Estimate of the Levels of Radon in Drinking
Water?
A. General Patterns of Radon Occurrence
Radon levels in ground water in the United States are generally
highest in New England and the Appalachian uplands of the Middle
Atlantic and Southeastern States. There are also isolated areas in the
Rocky Mountains, California, Texas, and the upper Midwest where radon
levels in ground water tend to be higher than the United States
average. The lowest ground water radon levels tend to be found in the
Mississippi Valley, lower Midwest, and Plains States. The following map
shows the general patterns of radon occurrence in those States for
which data are available.
BILLING CODE 6560-50-P
[[Page 59308]]
[GRAPHIC] [TIFF OMITTED] TP02NO99.008
BILLING CODE 6560-50-C
[[Page 59309]]
In addition to large-scale regional variation, radon levels in
ground water vary significantly over a smaller area. Local differences
in geology tend to greatly influence the patterns of radon levels
observed at specific locations. (This means, for example, that not all
radon levels in New England are high and not all radon levels in the
Gulf Coast region are low). Over small distances, there is often no
consistent relationship between radon levels in ground water and
uranium or other radionuclide levels in the ground water or in the
parent bedrock (Davis and Watson 1989). Similarly, no significant
geographic correlation has been found between radon levels in
groundwater systems and the levels of other inorganic contaminants.
Radon may be found in groundwater systems where other contaminants (for
example, arsenic) also occur. However, finding a high (or low) level of
radon does not indicate that a high (or low) level of other
contaminants will also be found. Similarly, there is little evidence
that radon occurrence is correlated with the presence of organic
pollutants. In estimating the costs of radon removal, EPA has taken
into account the fact that other contaminants, such as iron and
manganese, may also be present in the water. High levels of iron and
manganese may complicate the process of radon removal and increase the
costs of mitigation.
Radon is released rapidly from surface water. Therefore, radon
levels in supplies that obtain their water from surface sources (lakes
or reservoirs) are very low compared to groundwater levels.
Because of its short half life, there are relatively few man-made
sources of radon exposure in ground water. The most common man-made
sources of radon ground water contamination are phosphate or uranium
mining or milling operations and wastes from thorium or radium
processing. Releases from these sources can result in high ground water
exposures, but generally only to very limited populations; for
instance, to persons using a domestic well in a contaminated aquifer as
a source of potable water (USEPA 1994a).
B. Past Studies of Radon Levels in Drinking Water
A number of studies of radon levels in drinking water were
undertaken in the 1970s and early 1980s. Most of these studies were
limited to small geographic areas, or addressed systems that were not
representative of community systems throughout the U.S. The first
attempt to develop a comprehensive understanding of radon levels in
public water supplies was the National Inorganics and Radionuclides
Survey (NIRS), which was undertaken by the EPA in 1983-1984. As part of
NIRS, radon samples were analyzed from 1,000 community groundwater
systems throughout the United States. The size distribution of systems
sampled was the same as the size distribution of groundwater systems in
U.S., and the geographic distribution was approximately consistent with
the regional distribution of systems. Because of the limited number of
samples, however, the number of radon measurements in some States was
quite small. Table XI.B.1 summarizes the regional patterns of radon in
drinking water supplies as seen in the NIRS database.
Table XI.B.1.--Radon in Community Ground Water Systems by Region (All System Sizes)
----------------------------------------------------------------------------------------------------------------
Geometric
Region Arithmetic mean Geometric mean standard
(pCi/L) (pCi/L) deviation (pCi/L)
----------------------------------------------------------------------------------------------------------------
Appalachian............................................ 1,127 333 4.76
California............................................. 629 333 3.09
Gulf Coast............................................. 263 125 3.38
Great Lakes............................................ 278 151 3.01
New England............................................ 2,933 1,214 3.77
Northwest.............................................. 222 161 2.23
Plains................................................. 213 132 2.65
Rocky Mountains........................................ 607 361 2.77
----------------------------------------------------------------------------------------------------------------
Source: USEPA 1999g.
Note: These distributions are described in two ways. First, the arithmetic means (average values) are given. In
addition, the geometric mean and geometric standard deviation are given. This approach is taken because the
distributions of radon in groundwater systems are not ``normal'' bell-shaped curves. Instead, like many
environmental data sets, it was found that the logarithms of the radon concentrations were normally
distributed (``lognormal distribution.'') The geometric mean corresponds to the center of a bell-shaped
``normal'' distribution when radon concentrations are expressed in logarithms. The geometric standard
deviation is a measure of the spread of the bell-shaped curve, expressed in logarithmic form.
The NIRS has the disadvantage that the samples were all taken from
within the water distribution systems, making estimation of the
naturally occurring influent radon levels difficult. In addition, the
NIRS data provide no information to allow analysis of the variability
of radon levels over time or within individual systems. Thus, while the
NIRS data provide statistically valid estimates of radon levels in the
systems that were sampled, they do not adequately represent radon
levels in some individual States, especially in large systems.
The NIRS data formed the basis for EPA's first estimates of the
levels of radon in community groundwater systems in the United States
(Wade Miller 1990). They formed the basis for estimating the impacts of
EPA's 1991 Proposed Rule. These estimates were updated in 1993, using
improved statistical methods to estimate the distributions of radon in
different size systems (Wade Miller 1993.)
C. EPA's Most Recent Studies of Radon Levels in Ground Water
EPA's current re-evaluation of radon occurrence in ground water
(USEPA 1999g) uses data from a number of additional sources to
supplement the NIRS information and to develop estimates of the
national distribution of radon in community ground water systems of
different sizes. EPA gathered data from 17 States where radon levels
were measured at the wellhead, rather than in the distribution systems.
The Agency then evaluated the differences between the State (wellhead)
data and the NIRS (distribution system) data. These differences were
then used to adjust the NIRS data to make them more representative of
ground water radon levels in the States where no direct
[[Page 59310]]
measurements at the wellhead had been made. EPA solicits any additional
data on radon levels in community water systems, particularly in the
largest size categories.
Table XI.C.1 summarizes EPA's latest estimates of the distributions
of radon levels in ground water supplies of different sizes. It also
provides information on the populations exposed to radon through
community water systems (CWS). In this table, radon levels and
populations are presented for systems serving population ranges from 25
to greater than 100,000 customers. The CWSs are broken down into the
following system size categories:
Very very small systems (25-500 people served), further
subdivided into 25-100 and 101-500 ranges, in response to comments
received on the 1991 proposal;
Very small systems (501-3,300 people);
Small systems (3,301-10,000 people);
Medium systems (10,001-100,000 people); and
Large systems (greater than 100,000 people).
Table XI.C.1.--Radon Distributions in Community Groundwater Systems
----------------------------------------------------------------------------------------------------------------
System Size (Population Served)
-----------------------------------------------------------------------------------
25-100 101-500 501-3,300 3,301-10,000 >10,000 All systems
----------------------------------------------------------------------------------------------------------------
Total Systems............... 14,651 14,896 10,286 2,538 1,536 43,907
Geometric Mean Radon Level, 312 259 122 124 132 232
pCi/L......................
Geometric Standard Deviation 3.0 3.3 3.2 2.3 2.3 3.0
Arithmetic Mean............. 578 528 240 175 187 442
Population Served (Millions) 0.87 3.75 14.1 14.3 55.0 88.1
Radon Level, pCi/L.......... Proportions of Systems Exceeding Radon Levels (percent)
100......................... 84.7 78.7 56.9 60.4 62.9 74.0
300......................... 51.4 45.1 22.1 14.3 16.2 39.0
500......................... 33.6 29.1 11.4 4.6 5.5 24.2
700......................... 23.4 20.3 6.8 1.8 2.3 16.5
1000........................ 14.7 12.9 3.6 0.6 0.8 10.2
2000........................ 4.7 4.4 0.8 0.0 0.1 4.9
4000........................ 1.1 1.1 0.1 0.0 0.0 0.8
----------------------------------------------------------------------------------------------------------------
Sources: USEPA 1999g; Safe Drinking Water Information System (1998).
Systems were broken down in this fashion because EPA's previous
analyses have shown that the distributions of radon levels are
different in different size systems. In the updated occurrence
analysis, insufficient data were available to accurately assess radon
levels in various subcategories of largest systems. Thus, data from the
two largest size categories were pooled to develop exposure estimates.
D. Populations Exposed to Radon in Drinking Water
Based on data from the Safe Drinking Water Information System
(SDWIS), the Agency estimates that approximately 88.1 million people
were served by community ground water systems in the United States in
1998. Using the data in Table XI.C.1, systems serving more than 500
people account for approximately 95 percent of the population served by
community ground water systems, even though they represent only about
33 percent of the total active systems. The largest systems (those
serving greater than 10,000 people) serve approximately 62.5 percent of
the people served by community ground water systems, even though they
account for only 3.5 percent of the total number of systems.
As noted previously, the average radon levels vary across the
system size categories. As shown in Table XI.C.1, the average system
geometric mean radon levels range from approximately 120 pCi/L for the
larger systems to 312 pCi/L for the smallest systems. The average
arithmetic mean values for the various system size categories range
from 175 pCi/L to 578 pCi/L, and the population-weighted arithmetic
mean radon level across all the community ground water supplies is 213
pCi/L (calculations not shown). The bottom panel of Table XI.C.1 shows
the proportions of the systems with average radon levels greater than
selected values.
Table XI.D.1 presents the total populations in homes served by
community ground water systems at different radon levels, broken down
by system size category. These data show that approximately 20 percent
of the total population served by community ground water systems are
served by systems where the average radon levels entering the system
exceed 300 pCi/L and 64 percent of this population are served by
systems with average radon levels above 100 pCi/L. Less than one-tenth
of one percent of the population is served by systems obtaining their
water from sources with radon levels above 4,000 pCi/L.
Table XI.D.1.--Population Exposed Above Various Radon Levels by Community Ground Water System Size (Thousands)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Very very small Very Small Small Medium Large
Radon level (pCi/L) --------------------------------------------------------------------------------- Total
25-100 101-500 501-3,300 3,301-10K 10K-100K >100K
--------------------------------------------------------------------------------------------------------------------------------------------------------
4,000.................................................... 9.4 46 20 0.2 0.9 0.4 77.2
2,000.................................................... 41 183 119 5.7 21.7 11.0 381
1,000.................................................... 128 541 513 85.5 289 147 1,695
700...................................................... 202 848 962 267 859 436 3,558
500...................................................... 290 1,210 1,620 672 2,070 1,050 6,893
300...................................................... 445 1,880 3,140 2,080 6,060 3,070 16,641
100...................................................... 733 3,290 8,080 8,760 23,400 11,900 56,054
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 59311]]
XII. What Are the Risks of Radon in Drinking Water and Air?
A. Basis for Health Concern
The potential hazard of radon was first identified in the 1940s
when an increased incidence of lung cancer in Bohemian underground
miners was shown to be associated with inhalation of high levels of
radon-222 in the mines. By the 1950s, the hazard was shown to be due
mainly to the short half-life progeny of radon-222. Based on a clear
relationship between radon exposure and risk of lung cancer in a number
of studies in miners, national and international health organizations
have concluded that radon is a human carcinogen. In 1988, the
International Agency for Research on Cancer (IARC 1988) convened a
panel of world experts who agreed unanimously that sufficient evidence
exists to conclude that radon causes cancer in humans and in
experimental animals. The Biological Effects of Ionizing Radiation
(BEIR) Committee (NAS 1988, NAS 1999a), the International Commission on
Radiological Protection (ICRP 1987), and the National Council on
Radiation Protection and Measurement (NCRP 1984) also have reviewed the
available data and agreed that radon exposure causes cancer in humans.
EPA has concurred with these determinations and classified radon in
Group A, meaning that it is considered by EPA to be a human carcinogen
based on sufficient evidence of cancer in humans. After smoking, radon
is the second leading cause of lung cancer deaths in the United States
(NAS 1999a).
Most of the radon that people are exposed to in indoor and outdoor
air comes from soil. However, radon in ground water used for drinking
or other indoor purposes can also be hazardous. When radon in water is
ingested, it is distributed throughout the body. Some of it will decay
and emit radiation while in the body, increasing the risk of cancer in
irradiated organs (although this increased risk is significantly less
than the risk from inhaling radon). Radon dissolved in tap water is
released into indoor air when it is used for showering, washing or
other domestic uses, or when the water is stirred, shaken, or heated
before being ingested. This adds to the airborne radon from other
sources, increasing the risk of lung cancer (USEPA 1991, 1994a; NAS
1999b).
B. Previous EPA Risk Assessment of Radon in Drinking Water
1. EPA's 1991 Proposed Radon Rule
Because initial information on the cancer risks of radon came from
studies of underground miners exposed to very high radon levels, not
much consideration was given to non-occupational radon exposure until
recently. As new miner groups at lower radon exposure levels were added
to the data base, it became evident that radon exposures in indoor air,
outdoor air, and drinking water might be important sources of risk for
the U.S. population. In 1991, as part of developing a regulation for
radionuclides and radon in water as required by the 1986 Safe Drinking
Water Act, EPA drafted the Radon in Drinking Water Criteria Document
(USEPA 1991) to assess the ingestion and inhalation risk associated
with exposure to radon in drinking water. EPA estimated that a person's
risk of fatal cancer from lifetime use of drinking water containing one
picocurie of radon per liter (1 pCi/L) is close to 7 chances in 10
million (7 x 10--7). Based on this and other
considerations, EPA proposed a rule for regulating radon levels in
public water systems (56 FR 33050).
2. SAB Concerns Regarding the 1991 Proposed Radon Rule
The Radiation Advisory Committee of EPA's Science Advisory Board
(SAB) reviewed EPA's draft criteria document and proposed rule and
identified a number of issues that had not been adequately addressed,
including: (a) Uncertainties associated with the models, model
parameters, and final risk estimates; (b) high exposure from water at
the point of use (e.g., shower); (c) risks from the disposal of
treatment byproducts; and (d) occupational exposure due to regulation
and removal of radon in drinking water. The SAB recommended that EPA
investigate these issues before finalizing the radon rule. The EPA
considered SAB's recommendations in developing the current proposal.
3. 1994 Report to Congress
In 1992, Congress passed Public Law 102-389 (the Chafee-Lautenberg
Amendment to EPA's Appropriation Bill). This law directs the
Administrator of the EPA to report to Congress on EPA's findings |
