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40 CFR Part 61 EPA 402-R-98-007
National Emission Standards
for Hazardous Air Pollutants
Comments and Response to Comments
NESHAPS; National Emission Standards for Radon Emissions
From Phosphogypsum Stacks
November 1998
U.S. Environmental Protection Agency
Office of Radiation and Indoor Air
Washington, D.C. 20460
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PREFACE
The Environmental Protection Agency (EPA) is promulgating revisions to 40 CFR Part
61, Subpart R, National Emission,Standards for Radon Emissions from Phosphogypsum Stacks.
This Background Information Document (BID)-Comments and Response to Comments has been
prepared in support of the final rulemaking. It contains an introduction, general comments on
EPA's approach, laboratory research and development, including sampling and certification, use
outside a laboratory setting, and sampling statistics.
Copies of this BID, in whole or in part, are available to all interested persons. For
additional information, contact Eleanor Thornton-Jones at (202) 564-9773 or write to:
Director, Radiation Protection Division
Office of Radiation and Indoor Air (6602J)
U.S. Environmental Protection Agency
401M Street, SW
Washington, D.C. 20460
An EPA contractor, S. Cohen & Associates, Inc., McLean, VA, provided significant
technical support in the preparation of this BID.
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LIST OF PREPARERS
Various staff members from EPA's Office of Radiation and Indoor Air and the Office of
General Counsel contributed to the development and preparation of this BID:
Julie Rosenberg
Director, Center for Federal Guidance, Reviewer
Air Standards and Communication
Pat Tilson
Environmental Scientist
Project Officer
Tim Backstrom
Attorney, Office of General Counsel
Reviewer
Byron Bunger
Economist
Reviewer
Eleanor Thornton-Jones Program Analyst
Reviewer
An EPA contractor, S. Cohen & Associates, Inc., McLean, VA, provided significant
technical support in the preparation of this BID.
in
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Response to Comments on Amendments to Subpart R
INTRODUCTION
The Environmental Protection Agency (EPA) is promulgating revisions to those portions
of its National Emission Standards for Hazardous Pollutants (NESHAPs) that address radon-222
emissions from phosphogypsum stacks, 40 CFR part 61, Subpart R (Subpart R) which concern:
1) the distribution and use of the substance, phosphogypsum, for indoor research and
development purposes; 2) the sampling and measurement of radium-226 in phosphogypsum; and
3) use of phosphogypsum for outdoor agricultural purposes. EPA is taking this action in
response to issues raised in a petition for reconsideration from The Fertilizer Institute (TFI) which
questioned aspects of the risk assessment EPA performed in support of the rulemaking that
revised Subpart R in 1992. The risk assessment was an evaluation of the risk to persons who
perform research and development activities in a laboratory using phosphogypsum.
Phosphogypsum ~ a byproduct of the wet-acid process of producing phosphoric acid from
phosphate rock - contains naturally occurring radiation emitted by uranium-238 and its decay
products such as radium-226 and radon-222. Exposure to the radiation emitted by these and
other radionuclides in phosphogypsum can increase an individual's probability of developing
cancer.
EPA published a notice of proposed rulemaking on May 8, 1996 and solicited comments
See 61 FR 20775, May 8, 1996. A total of 107 general and specific comments were received by
the docket and at the subsequent public hearing in Florida from 19 organizations and private
citizens. A small number of these comments were procedural in nature, requesting a public
hearing, asking that the comment period be extended, and acknowledging the extension of time to
submit comments. The request for a public hearing was granted. The vast majority of the
comments dealt with policy, legal and technical issues.
Comments are presented here in summary form under four categories that best describe
their content:
,1. General Comments on EPA's Approach
-2. Laboratory Research and Development, including Sampling and Certification
3. Use Outside a Laboratory Setting
4. Sampling Statistics .
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1. General Comments on EPA's Approach
Comment l.a: EPA's authority under the Clean Air Act is limited to ambient air. Air inside
laboratories does not fall within the Clean Air Act definition of ambient air, so EPA has no
authority to regulate the laboratory research and development uses of phosphogypsum. (TFI)
Response: This rulemaking is limited to reconsideration of certain specified issues, including the
amount of phosphogypsum that can be removed from stacks for use in research and development
and correction of the formula used to demonstrate that phosphogypsum removed from a stack
for agricultural purposes meets the 10 pCi/g limit. This comment addresses an issue presented by
the Subpart R rule promulgated in 1992 which is not among those under reconsideration in this
rulemaking. In any case, the commenter misunderstands the structure of the rule. When EPA
first promulgated Subpart R in 1989, it required that radon emissions be controlled by placement
of all phosphogypsum in a stack or mine. In response to that general prohibition, many parties
argued that it would effectively preclude other existing uses of phosphogypsum in activities such
as agriculture and research and development. In order for such uses to be permissible, it was then
necessary for EPA to make specific exceptions to the general requirement that all phosphogypsum
be disposed in stacks or mines, which EPA had determined would protect public health with an
ample margin of safety. EPA concluded that it would be inappropriate to amend the 1989
NESHAP to permit any alternative disposition of phosphogypsum if that alternative would
present potential health risks from radon emissions greater than those EPA would consider legally
permissible as part of disposal. If EPA were not permitted to establish procedures governing
distribution of phosphogypsum removed from a stack which would assure that exceptions to the
general requirement of disposal in a stack or mine would not themselves result in unacceptable
health risks, EPA believes that it would be irresponsible to permit such exceptions. Thus, analysis
by EPA of the risks presented by laboratory use of phosphogypsum is necessary to decide under
what circumstances EPA can make an exception to the general requirement that phosphogypsum
be disposed of in a stack or mine, not because it is the intent of EPA to establish a NESHAP
directly regulating radon emissions to air inside laboratories.
Comment l.b: While EPA has acknowledged that its original risk assessment contained errors,
the agency's response to its current risk assessment proposes that researchers demonstrate that
using more than 700 pounds of phosphogypsum in a laboratory project would be "helpful." This
approach is completely counter to the NESHAPs methodology set out in the Vinyl Chloride
decision. It is not the responsibility of the regulated community to show that an erroneous
limitation is a burden, but it is EPA's responsibility to determine an amount of phosphogypsum
that is presumptively safe to use in research and development and then determine whether,
considering all other factors, that quantity protects human health with an ample margin of safety.
There is no basis for EPA to reduce the amount of phosphogypsum to be used in laboratory
research and development below that which is presumptively safe. (TFI)
Response: This comment misconstrues the Vinyl Chloride decision. Under the methodology
required by that decision, once EPA has determined the level of emissions which is presumptively
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safe, EPA must then establish an additional margin of safety. In this second step, EPA is required
to consider factors such as the economic feasibility of greater control. If there were no practical
utility associated with the ability to use more than a specified amount of phosphogypsum in a
laboratory setting, then it would be appropriate for EPA to establish a limitation which reflected
this conclusion.
However, based on the record in this rulemaking, EPA has concluded that the ability to use
greater quantities of phosphogypsum in a laboratory setting does have practical utility. Since the
corrected risk analysis demonstrates that the use of 7,000 pounds of phosphogypsum for indoor
research and development presents a lifetime risk to the maximally exposed individual which EPA
has deemed presumptively safe under the applicable quantitative criteria, EPA has decided to
revise Subpart R to permit such use.
Comment l.c: EPA must consider the quantity and value of phosphogypsum in evaluating its
stance on phosphogypsum research, since that research is consistent with reuse and recycling
approaches to waste management. The work of the phosphate industry, FIPR, and LSU has led
to many possible uses. EPA has not shown either the understanding the industry expected or
provided necessary support through the regulatory process, by eliminating all research uses, then
by placing very stringent limitations on research and development based on a risk assessment that
the Agency acknowledges included significant errors. TFI supports the proposed modifications to
the 1992 rule, but EPA should reevaluate its entire approach to phosphogypsum research and
development to encourage sound research and development on reuse while still protecting human
health and the environment. (TFI)
Response: EPA has determined that its approach, allowing laboratory research and development
projects using limited quantities of phosphogypsum, is safe, with an ample margin of safety. This
research and development has the potential for finding ways to promote reuse and recycling of
phosphogypsum. In increasing the limit on the amount of phosphogypsum .that can be used in
research and development, the Agency is seeking to assure that the proper balance is reached
between the benefits of such research and development and the risks posed by the use of
phosphogypsum. In this way, EPA is promoting research and development on reuse and recycling
of phosphogypsum.
Comment l.d: EPA's proposed limitation of 7,000 pounds of phosphogypsum per laboratory is
better than the former limit of 700 pounds per experiment, but the higher limit appears to be as
much for EPA's enforcement convenience as for research flexibility. Enforcement convenience is
not a sufficient basis for establishing regulatory limits. EPA should determine a limit per research
and development project that is presumptively safe and request comments on various regulatory
approaches. (TFI, IMC-Agrico)
Response: The Agency's decision to allow the use of 7,000 pounds of phosphogypsum for
research and development is based, on a revised risk assessment; not on enforcement convenience.
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Comment l.e: The limited and controlled nature of all three types of phosphogypsum research
and development (bench scale work in labs, "pot" scale work in greenhouses, and field studies)
make substantive command and control regulation unnecessary! Procedural requirements,
including notice of the radionuclide content of phosphogypsum involved in particular projects,
and, if necessary, deed restrictions and other notice requirements to control access to field
research and development sites are sufficient to protect human health - of both researchers and the
general public - with an ample margin of safety. (TFI)
Response: The Agency's policy is to establish limits on the amount of phosphogypsum that can
be used in a laboratory, and to allow researchers the freedom to conduct their work within that
constraint. The reporting of the radium-226 content of phosphogypsum used in research and
development is no longer required. Outdoor research and development is not permitted under
Section 61.205. Researchers who wish to undertake field studies utilizing phosphogypsum in a
manner not permitted under Section 61.204 may apply for permission to undertake such studies
under Section 61.206. Applicants under Section 61.206 are free to propose any restrictions that
they believe will assure that the risk from a proposed alternative use is kept within acceptable
levels.
Comment 1 .f: EPA should not change the existing NESHAP to allow any increase in the quantity
of phosphogypsum available for research and development uses or allow more than one project
per site. There is considerable evidence that the linear non-threshold relationship is the best tool
to predict the risks of radiation exposure at low doses, despite the position taken by some
members of the Health Physics Society. It is more difficult to control and monitor 7,000 than 700
pounds of phosphogypsum; expanded use will increase cancers in laboratory personnel. EPA
should increase, rather than decrease, restrictions on the use of phosphogypsum, or at the
minimum, maintain the current restrictions, and alternative uses should not be permitted. (Envir.
Confederation, Brown, Behrens, ManaSota-88)
Response: EPA has determined that 7?000 pounds in laboratory research'and development use to
be safe, with an ample margin of safety, so long as this limit is not exceeded for any individual
research activity and no one room within the facility contains more than this limit. The Agency
does not believe that facilities conducting research and development activities involving
phosphogypsum will exercise any less care in storing and handling the larger quantities of material
permitted under the revised NESHAP than they did in storing and handling the 700 pounds
previously allowed.
Comment l.g: New studies show that linear no-threshold assumptions are not completely
accurate and grossly overestimate cancer risk. The linear no-threshold hypothesis has not been
proven; research conducted and evidence obtained over the last decade calls this hypothesis into
question. The Health Physics Society's recent position statement on low-level radiation exposure
recommends against quantitative estimation of health risk below an individual dose of 5,000 mrem
in one year or a lifetime dose of 10,000 mrem in addition to background radiation. The Society
holds that risk estimation in this dose range should be strictly qualitative, emphasizing a range of
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hypothetical health outcomes within an emphasis on the likely possibility of no adverse effects at
all. In addition, the dose rate that has been estimated for a phosphogypsum researcher is much
lower than 5,000 mrem/yr. (Simplot, Gidry)
Response: The Agency position is that the assumption of no threshold and a linear response is
prudent public policy. In conducting risk assessments, EPA must take into account the limitations
and uncertainties in our scientific knowledge about the effects of radiation at all levels of
exposure. An annual exposure to 5,000 mrem would pose a risk far in excess of that determined
to be safe, with an ample margin of safety, which is a lifetime risk to the maximally exposed
individual no greater than 1 x 10"4.
Comment l.h: Industry should be required to use a phosphoric process that creates no
phosphogypsum or other hazardous byproducts, as indicated by the Phosphoric Acid Dialogue
Committee. (ManaSota-88)
Response: This comment is beyond the scope of the issues subject to reconsideration in this
rulemaking. In any case, since the risks posed by releases of radionuclides from phosphogypsum
can be maintained at levels that protect public health with an ample margin or safety, there is no
basis for utilizing a NESHAP to prohibit the production of phosphates by the wet acid process.
2. Laboratory Research and Development, including Sampling and Certification
Comment 2.a: An aggregate limit of 7,000 pounds of phosphogypsum per facility for research
purposes is better than the 700 pound limit per experiment, the 7,000 pound limit will still restrict
research in removing radium from phosphogypsum. At 30 pCi/g, there are less than 10
micrograms by weight of radium-226 in 700 pounds of phosphogypsum, making separation
research difficult. In 7,000 pounds, there are still less than 100 micrograms available. Milligram
quantities of radium are needed for effective separation research. The larger limit also will permit
experiments that are more realistic in size, providing better data and yielding results about using
phosphogypsum that are more accurate. The larger amount per facility would also provide a
more homogeneous supply of phosphogypsum, which is important to providing relationships
among research and development projects and more flexibility in their development. A larger
stockpile would also allow better control of the phosphogypsum by supporting a central
controlled access area, rather than individual project storage areas. (FIPR, TFI, Scott, Gidry,
Seals)
The proposed 7,000 pound limit for a given facility is preferable to setting a limit for each
individual experiment. Even with this limit, the risk would be less than estimated by EPA, as no
laboratory will ever have 7,000 pounds of phosphogypsum on hand every day of the year. The
average amount would probably not be more than 2,000 pounds. (FIPR)
Response: The limit on the amount of phosphogypsum that can be used in a laboratory was
determined to protect those researchers that work with 7,000 pounds of phosphogypsum on a
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continuous basis. This 7,000 pound limit applies separately to each individual research and
development activity. The final rule protects researchers in those rooms in laboratories in which
7,000 pounds of phosphogypsum is used. No more than 7,000 pounds may be stored, or in use in
ongoing experiments, in any room at a research and development facility. A particular facility
may possess more than 7,000 pounds of phosphogypsum for use in multiple research activities, so
long as it does not exceed this limit for any individual research activity and no one room within
the facility contains more than this limit.
Although it is likely that many laboratories will hold less than 7,000 pounds at any one
time, much of the phosphogypsum on hand in a laboratory at a time may be in use in ongoing
experiments, rather than stockpiled in barrels awaiting use.
Comment 2.b: There should be no limitation on multiple research and development activities at a
single facility or by a particular principal investigator, since the actual time the investigator spends
in the laboratory working with phosphogypsum is limited, usually to a maximum of 2 to 3 hours a
day, less than 5 days a week, for a maximum of 150 days a year. An increase to 7,000 pounds of
phosphogypsum for multiple research projects would therefore be very unlikely to result in
unacceptable worker exposure. Given limited storage space in most research laboratories,
phosphogypsum would not be stored in the laboratories, but brought in only on an as-needed
basis. The nearly universal practice is to store phosphogypsum outside in 5-gaIlon pails. No more
than 2 pails are in active use at any one time. (FIPR, Seals)
Response: The Agency agrees that, within the overall limit of 7,000 pounds per room, no limit on
the number of research and development activities at a given facility is necessary.
Comment 2.c: Using 7,000 pounds of phosphogypsum will not appreciably increase the overall
risk of working in a laboratory, when one considers other hazards such as chemical, electrical, or
fire in that setting. In addition, there should be no limit on multiple research and development
activities at any facility or by any investigator. EPA's indoor radon screening criterion of 4 pCi/1
would allow about 500,000 pounds of phosphogypsum in a research laboratory, an essentially
unlimited amount. Other radiation/carcinogen risks deemed acceptable (from air travel, food,
dwelling construction) because they are so small have not been regulated. (Scott, Gidry)
Response: EPA acknowledges that working in a laboratory exposes individuals to a broad
spectrum of risks. However, this does not obviate EPA's responsibility for protecting the public
health of laboratory workers with an ample margin of safety. The Agency's screening level of
4 pCi/1 for indoor radon was established for a different purpose. NESHAPs promulgated under
the Clean Air Act Section 112 must achieve a maximum individual lifetime risk not to exceed
1 x 1014.
Comment 2.d: Radium extraction experiments with more than 700 pounds of phosphogypsum
could cause higher exposures than simple handling and storage. There is no information about the
exposures from radium extraction in the record. (ManaSota-88)
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Response: The Agency does not believe that research into radium extraction would result in
significantly different exposure pathways causing higher risk than those evaluated in its risk
assessments for other research and development uses of phosphogypsum. In fact, much research
would likely involve wet chemistry, which will significantly reduce radon-222 emissions compared
to other handling activities.
Comment 2.e: Three respondents stated that the requirement for an owner/operator of a
phosphogypsum stack to sample the phosphogypsum to be released for research and development
uses should be removed. It is not needed, as there is no limitation on the radium content of
phosphogypsum used for research and development, and in any case, researchers will determine
the radium content. Eliminating the certification requirement would result in most research and
development facilities maintaining a lower phosphogypsum inventory, since it would be easier to
replace the phosphogypsum consumed in research activities. Two other respondents stated the
opposite: that the requirement for stack owners/operators to analyze the radium content of the
phosphogypsum they release should not be eliminated, due to the potential risk of cancer and the
potential mixing of phosphogypsum from different stacks for research and development. The cost
to analyze phosphogypsum has been cited as about $200 per 55-gallon drum, which is
insignificant. (FIPR, TFI, Florida Phosphate Council; ManaSota-88, Sheppard)
Response: The Agency supports research and development that may derive benefits from the
utilization of phosphogypsum, so long as this research can be carried out safely. The risk analysis
demonstrates that the risk from storing and using 7,000 pounds of phosphogypsum in a laboratory
is safe, with an ample margin of safety. EPA has not sought to limit laboratory use of
phosphogypsum with higher radium levels, and the EPA risk assessment assumes that
phosphogypsum used in a laboratory setting will contain higher activity levels. Therefore, the
current requirement that the radium-226 content in the phosphogypsum used in research and
development be measured serves no useful purpose and has been removed from the rule.
Comment Zf: While a greenhouse may be regarded as a laboratory for legal and policy purposes,
raising the issue of EPA's authority to regulate the air inside the greenhouse, the fact that air
exchanges in greenhouses are substantially higher than those in laboratories located in permanent
structures and the fact that researchers generally spend much less time in greenhouses than at
bench-scale work in laboratories both significantly reduce potential exposures for researchers. In
addition, the assumption of two air changes pet hour in a laboratory using 7,000 pounds of 26
pCi/g phosphogypsum is likely to be incorrect by a factor of 400 to 500 percent, given the OSHA
recommendation of 4 to 12 air changes per hour, and a 1995 study that shows that the typical
number of air changes in laboratories is at the high end in the range of 1 to 10 air changes per
hour. Based on the OSHA recommendation alone, EPA's assumption of two changes per hour is
low by at least 100 percent. (TFI, Gidry, Simplot)
Response: The Agency recognizes that greenhouses may have more air changes per hour than
laboratories and that researchers may spend fewer hours in greenhouses. However, the Agency is
promulgating a rule that applies to all indoor research and development activities involving
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phosphogypsum. It is Agency policy to select parametric values that are reasonable in evaluating
risk.
Comment 2.g: The risk analysis allowing the use of 7,000 pounds of phosphogypsum is based on
a ventilation rate of two air changes per hour to remove radon and a gamma exposure based on an
average level of shielding and proximity of a researcher to the phosphogypsum. These two types
of exposure can be varied to allow more phosphogypsum to be used, since the level of
radioactivity in the phosphogypsum should determine the ventilation rate and the shield thickness
required. For example, using the equation given in the risk assessment for the steady-state radon
concentration of radon in laboratory air, the area of exposed phosphogypsum allowed in a
laboratory can be calculated for a given ventilation rate and radium concentration. A greater
ventilation rate would be needed for phosphogypsum containing more radium or for a greater
exposed area. A similar analysis holds for gamma exposure and the amount of shielding needed.
The regulation should indicate the maximum radon concentration and the maximum gamma
emission, rather than a specific amount and concentration. (Simplot)
Response: The proposed regulatory approach described in Comment 2.g. would be considerably
more difficult and burdensome to implement than the rule promulgated by the Agency in 1992,
and being revised today. In addition to requiring data on the ratlium-226 content of the
phosphogypsum, it would require detailed evaluation of ventilation rates, shielding, and exposure
geometries. By contrast, the limitation on the quantity within a facility simply requires the facility
to limit its inventory.
Comment 2.h: EPA's analysis overestimates the risk to phosphogypsum researchers because it
was not conducted in accordance with the recommendation of the ICRP that potential doses be
multiplied by their probability of occurrence. All of EPA's exposure assumptions are treated as
though they will occur. Distribution data can be used to estimate the probability of occurrence for
the parameters assumed. (Gidry)
Response: The Agency is familiar with the recommendations of the ICRP and other advisory
groups. However, EPA's NESHAPs, such as Subpart R, are based on the exposure to the
maximally exposed individual, in conformance with the provisions of the Vinyl Chloride decision,
using the framework of the Benzene NESHAP. In doing this, the EPA ensures that the
NESHAPs protect the health of even the most exposed individual regardless of the likelihood of
that individual's becoming exposed.
Comment 2.i: EPA's multi-laboratory geometry, used for exposure calculations in the risk
assessment, is highly improbable, and assumes no credit for shielding from walls or floors. This
risk assessment is highly conservative, and EPA finds the risk to be acceptable, so more realistic
conditions should provide an even greater "ample margin of safety." (Chambers)
Response: The Agency believes that its risk analysis meets the needs of estimating the maximum
individual risk in a multi-laboratory setting.
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Comment 2.i: In 1992, EPA determined that the presumptively safe level is a maximum individual
risk of 1 x 10"4. It also removed the blanket prohibition on research and development activities.
the Agency concluded that those conditions would protect public health with an ample margin of
safety. Thus, EPA has already found that where the risk from phosphogypsum research and
development is less than 1 x 10"4, there is an ample margin of safety. The only thing that changed
between 1992 and 1996 is that EPA found its risk assessment was flawed and severely
understated the amount of phosphogypsum associated with that presumptively safe risk level.
EPA should therefore increase the limit of phosphogypsum that can be used in research and
development, consistent with the corrected risk assessment findings. (TFI)
Response: EPA agrees and has done so with this rulemaking.
Comment 2.k: EPA's assumption that a researcher spends 1,000 hours per year (about 4 hours
per working day) at an average distance of 1 meter from a drum of phosphogypsum is too
conservative. A researcher typically spends only a few hours per week at a distance of 1 meter
and the remainder of the approximately 20 hours per week at a much greater distance. The
assumed phosphogypsum-contaminated air dust concentration of 100 micrograms per cubic meter
is also unreasonably conservative, as this degree of concentration could only occur (if it occurs at
all) when the phosphogypsum was being sampled or otherwise disturbed. (TFI)
Response: The Agency's choice of exposure parameters and scenarios is consistent with its
policy to set standards which protect the health of the maximally exposed individual.
Comment 2.1: The assumption that researchers using phosphogypsum are exposed for only 10
years is not supported by the record. Exposure times may be much longer. (ManaSota-88)
Response: The Agency agrees that no typical exposure period can be determined from the
available information and that some workers might incur exposures over a period longer than 10
years. However, the Agency believes that using an exposure time of 10 years is reasonable, given
the values assigned to other exposure parameters (hours per day, distance from the source, etc.)
that affect the risk estimate.
Comment 2.m: Any radon build-up in a closed drum typically occurs within the first two weeks,
with longer storage having no significant effect since radon build-up is limited by equilibrium.
Radon will be distributed through the pore spaces of the phosphogypsum, rather than build up on
top of the phosphogypsum in the barrel. There would probably be only a slight increase in radon
over that released from an open drum. There would be no gamma radiation problem because the
drum would act as shielding. In addition, EPA's assumption that research and development
drums of phosphogypsum are open would allow the water to evaporate, which would foreclose
effective research. A closed drum provides significant shielding from gamma radiation. (TFI,
Scott, Simplot)
Response: The Agency agrees that equilibrium in an undisturbed drum will be reached within a
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few weeks, with the radon distributed in the pore spaces of the phosphogypsum. However, the
Agency does not agree that it should ignore the possibility of an open drum over long periods of
time simply because some research plans would be impractical if the material were allowed to dry
out. Finally, the Agency's estimates of the gamma exposure do take into account the geometry of
the storage drum and the shielding that it would provide.
3. Use Outside a Laboratory Setting
Comment 3.a: The statement in Section 61.206(c), that proposed phosphogypsum use or
distribution must protect public health to the same degree as disposal in a stack or mine is a test
for determining a safe or acceptable level, not for establishing an ample margin of safety, as
required under Clean Air Act Section 112. Ample margin is to be determined on a case-by-case
basis, considering alternatives to the proposed use or distribution, so the ample margin provided
by disposal in stacks or mines cannot be transferred to another use. Placing field research under
Section 206, without providing evaluation criteria for field research projects, creates an invalid
rule. (ManaSota-88)
Response: This rulemaking is limited to the reconsideration of the amount of phosphogypsum
that can be used for research and development and to correct the formula used to demonstrate
that phosphogypsum removed from a stack for agricultural purposes meets the 10 pCi/g limit.
This comment addresses an issue of the 1992 rulemaking itself, which is not under reconsideration
here. EPA is now developing a document laying out the procedures for applying for an
alternative use application.
Comment 3.b: It is not correct that Section 61.205 provides the exclusive basis for authorized
research and development activities, as contended at the hearing. This position would preclude
EPA from approving a project where the risk was shown to be much smaller than 1 x 10*4, clearly
not the intended result, as EPA has stated in Section 61.206. Section 61.205 provides the generic
prescribed conditions under which EPA has determined that phosphogypsum can be used with an
ample margin of safety. Those generic conditions cannot preclude other research and
development uses that can also be conducted with an ample margin of safety. (TFI)
Response: Section 61.205 is revised to confirm the intent of EPA that it apply only to indoor
laboratory research and development. Outdoor uses of phosphogypsum must comply with either
Section 61.204, "Distribution and use of phosphogypsum for outdoor agricultural purposes" or
Section 61.206, "Distribution and use of phosphogypsum for other purposes." Section 21.206
allows EPA to authorize, on a case-by-case basis, indoor and outdoor uses not covered or
authorized by Sections 61.204 and 61.205. Phosphogypsum that remains in outdoor stacks must
comply with the numerical limits of Section 61.202.
Comment 3.c: Unlimited amounts of phosphogypsum can be used for agricultural purposes if the
radium content does not exceed 10 pCi/g. The limitation on field research should be the same.
Even at a higher radium content, 7,000 pounds of phosphogypsum should be allowed at any one
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field site, since a reasonable rate of application would limit the size of controlled test fields to a
relatively small number of acres. Controlled field studies contribute very little radon in excess of
background levels, and these slightly increased levels are insignificant compared to the indoor
standard of 0.02 Working Levels. Stack sampling data indicate no excess risk from radon due to
working on or very near a phosphogypsum stack (0.01 WL averaged across all four boundaries of
the stack), so there should be no radon danger from field studies, because the phosphogypsum
concentration would be reduced by the physical process of land application. Further, deed
restrictions or other forms of notice could be used to control later access if significant amounts of
phosphogypsum are left in place after a field study is completed. (FIPR, TFI)
Response: The 10 pCi/g restriction on the radium-226 content of phosphogypsum used in
agriculture was based on representative application rates and tillage practices in the U.S. This
limit applies to agricultural field uses, including those field uses which are for the purpose of
agricultural research and development. Research utilizing phosphogypsum containing more
than 10 pCi/g can be approved on a case-by-case basis under Section 61.206. The efficacy of
deed restrictions or other forms of notice in limiting potential risks can be considered in the
context of individual applications which propose them.
Comment 3.d: EPA's proposal to allow unrestricted agricultural application of 10 pCi/g
phosphogypsum, based on an annual application over 100 years, could be made even more
flexible by allowing similar applications of phosphogypsum with higher radium levels over a
shorter time. This should not change the risk significantly, if EPA would set a maximum amount
of phosphogypsum (perhaps 400 pounds per acre) that could be'applied over the period of an
agricultural research and development program. Evaluating requests following this pattern could
be approved more quickly and help simplify and reduce paperwork. (FIPR)
Response: EPA agrees that the risk assessment model used in deriving the 10 pCi/g limit for
agricultural applications of phosphogypsum under Section 204 could be used to determine
alternative radium-226 concentrations, application rates, and time periods of usage for
phosphogypsum that would meet an acceptable risk. In cases where there are applications dealing
with similar alternative uses, the Agency is prepared to streamline its approval process under
Section 206 to reduce the burden on applicants, provided their data demonstrate the projects meet
the 1 x W4 risk criteria. ,
Comment 3.e: Studies of radium uptake by plants would be severely constrained by a 700-pound
limitation, as a laboratory study showed no difference in radium uptake between rice plants grown
in a control medium and in phosphogypsum; this should be examined on a larger scale. Data from
plants growing on phosphogypsum stacks also often show little or no difference from those -
grown in a control medium; however, the numbers of samples are too small to properly assess
those results. Water hyacinths do show an increased radium uptake when grown in water with
phosphogypsum. However, for perspective, a person consuming a typical diet receives a dose of
about 1.5 mrem/yr. If consuming milk and meat from cattle grazing on a phosphogypsum test
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plot, the annual total additional dose would be 0.15 mrem. For vegetables such as radishes and
kale, the additional dose would be about 0.18 mrem/yr. (Scott)
Response: This rulemaking is limited to the reconsideration of the amount of phosphogypsum
that can be used for research and development and to correct the formula used to demonstrate
that phosphogypsum removed from a stack for agricultural purposes meets the 10 pCi/g limit.
This comment addresses the 1992 rulemaking itself, which is not under reconsideration here. In
any case, the limit on the radium content of phosphogypsum used in agriculture is based on risks
associated with subsequent occupancy of treated land, not on any hypothetical dietary exposures.
The limit on indoor research and development is being increased to 7,000 pounds with this
rulemaking.
Comment 3.f: With no limit on the quantity of phosphogypsum that can be used in field studies
(the research and development limit does not apply), any such study must be specifically approved
by EPA. This currently requires the applicant to provide a full risk assessment acceptable to the
agency. EPA has not provided: 1) guidance on the content of the required risk assessment, 2) a
consistent approach and standards for approval of field study requests by regional offices, and 3) a
defined time period for EPA review of risk assessments and applications. This situation is unduly
burdensome to industry. The individual approval regulatory scheme that applies to
phosphogypsum field studies is therefore arbitrary and capricious. If EPA continues to require
individual approval for phosphogypsum field studies, it must develop protocols for seeking and
granting those approvals, talcing into account two main issues. First, the protocols should include
a "tiering" process, under which smaller, more limited field studies can be approved on the basis
of a screening analysis rather than a complete risk assessment. Second, field studies that are the
same or similar to those already approved after a full risk assessment should not have to duplicate
that risk assessment: the subsequent studies should be required only to address the relevant
differences between the projects. Further, field studies that do not result in permanent
installations should not be required to provide a formal risk assessment. (TFI, Seals, Florida
Phosphate Council)
Response: This rulemaking is limited to the reconsideration of the amount of phosphogypsum
that can be used for research and development and to correct the formula used to demonstrate
that phosphogypsum removed from a stack for agricultural purposes meets the 10 pCi/g limit.
This comment addresses the 1992 rulemaking itself, which is not under reconsideration here.
These issues were considered in the 1992 rulemaking and the Agency determined that the use of
phosphogypsum in agriculture and for research and development, under the limitations imposed
on its use, is safe. The Agency also provided for alternative use of phosphogypsum under the .
provisions of Section 61.206, where Agency approval is required for its use. Any applicant is
required to demonstrate that the alternative use meets EPA's risk requirements before the use can
be approved. The Agency shares the commenters' view that wherever possible, the application
process and review should be streamlined. Existing models and other precedents will be allowed
wherever appropriate to eliminate redundancy and unnecessary steps for applicants and EPA. In
response to specific issues raised in this comment: 1) EPA has been and will continue to be
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available to offer guidance to applicants and is developing comprehensive written guidance; (2)
All alternative use applications are approved at the EPA headquarters level, not at the regional
level, which assures that all applicants under Section 61.206 are evaluated in a consistent manner;
(3) Given the uniqueness, of each application, EPA cannot commit to a predetermined review
period. However, as stated above, where there are acceptable precedents, EPA will allow them as
part of an application.
Comment 3. g: Public health will not be protected if more field projects are allowed. Using
phosphogypsum as roadbed material and for agricultural purposes will contaminate soil,
groundwater, air, and vegetation as radium-226 is leached by traffic, flooding, rain, and other
weather conditions. Using phosphogypsum as landfill cover and to enhance waste decomposition
will contaminate the site for future use and expose landfill workers and the public to excess cancer
risk. This use will also contaminate ground and surface waters, as all landfills, lined or unlined,
eventually leak. Using phosphogypsum to make reefs in offshore waters is equivalent to dumping;
phosphorus will harm aquatic ecosystems, accumulate radionuclides and heavy metals, and
eventually enter the food chain thrpugh benthic feeders. Future use of land areas would have to
be restricted for thousands of years to protect public health. Deed restrictions for using
phosphogypsum in projects such as these are meaningless when used to secure an EPA exemption
for that use, because the applicant admits that phosphogypsum is harmful by agreeing to a deed
restriction. However, any deeds to lands that have been treated with phosphogypsum should still
state that fact. (ManaSota-88, Sheppard) .
Response: This rulemaking is limited to the reconsideration of the amount of phosphogypsum
that can be used for research and development and to correct the formula used to demonstrate
that phosphogypsum removed from a,stack for agricultural purposes meets the 10 pCi/g limit.
This comment addresses the 1992 rulemaking itself, which is not under reconsideration here.
These issues were considered in the 1992 rulemaking and the Agency determined that the use of
phosphogypsum in agriculture and for research and development, under the limitations imposed
On its use, is safe, with an ample margin of safety. The Agency also provided for alternative use
of phosphogypsum under the provisions of Section 61.206, where Agency approval is required
for its use. Any applicant is required to demonstrate that the alternative use meets EPA's risk
requirements before the use can be approved.
Comment 3.h: Use of phosphogypsum in roadbeds will contaminate soil, groundwater, air, and
vegetation by leaching, flooding, and traffic wear. Monitoring wells adjacent to a road
constructed with phosphogypsum have shown elevated radionuclide levels. (ManaSota-88)
Response: This rulemaking is limited to the reconsideration of the amount of phosphogypsum
that can be used for research and development and to correct the formula used to demonstrate
that phosphogypsum removed from a stack for agricultural purposes meets the 10 pCi/g limit.
This comment addresses the 1992 rulemaking itself, which is not under reconsideration here. Any
use of phosphogypsum for roadbed use would have to be approved under Section 61.206. Such
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use would be approved only if the applicant demonstrates that the requirements of Section 61.206
are satisfied.
4. Sampling Statistics
Comment 4.a: The rules requiring sampling across the area of the stack to be moved into
commerce need to be better defined, as the sampling requirements are burdensome and expensive.
The proposed requirements leave open several questions, such as:
- do underlying strata have to be sampled?
- will EPA require a new sampling program for each new stratum?
- does each shipment from a stratum have to be analyzed? (Simplot)
Response: No sampling is required for phosphogypsum removed from the stack for use in
research and development. For all other cases, the surface of the area from which
phosphogypsum is to be remove must be sampled once a year. The underlying strata do not need
to be sampled. The same sampling protocol must be used each time the surface of the area from
which the phosphogypsum is to be removed is sampled, that is a minimum of 30 samples must be
taken each time the area is sampled. Individual shipments do not need to be sampled provided
they have been removed from the area of the stack that was sampled and found to be less that 10
pCi/g by the procedures outlined in the rule and described in the document "Statistical Procedures
for Certifying Phosphogypsum for Entry into Commerce, as Required by Section 61.207 of 40
CFR Part 61, Subpart R" and provided that this sampling was performed no longer than one year
proceeding its removal.
Comment 4.b: According to the rule, apparently every stratum of phosphogypsum that might be
moved off the site must be sampled, with the number of samples to be determined by how close
the phosphogypsum is to the average radium-226 concentration of 10 pCi/g. The error bound of
the samples must be no more than 0.05. The explanation section of "Statistical Procedures for
Certifying..." assumes that the standard deviation among samples is 8.2 pCi/g. This equation
indicates that the closer to 10 pCi/g the radium-226 concentration of the phosphogypsum, the
required number of samples and thus the testing expenses increase rapidly, due to the stringent
error bound of 0.05. A regulation stating a total exposure limit based on the product of radium
concentration and area could solve this sampling problem. Regulations should require the same
knowledge of the error distribution of radium concentrations without regard to the actual
concentration, to allow the company to design their operation based on that knowledge, again
taking concentration and area into account. (Simplot)
Response: The test does not require that every stratum of the phosphogypsum in a stack be
sampled. It requires that the surface of the area from which phosphogypsum is to be removed
must be sampled annually. A minimum of 30 samples is needed in all cases. The number of
samples needed does increase as the true radium-226 concentration approaches 10 pCi/g. This is
a characteristic of the statistics underlying hypothesis testing. As stated in the rule, this situation,
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where the required sample size may be quite large, may cause the cost of sampling to increase to
the point that a stack operator may abandon the attempt to certify this area of the stack for the
removal of phosphogypsum. The standard deviation of 8.2 pCi/g used in the Appendix to
"Statistical Procedures for Certifying Phosphogypsum for Entry into Commerce, as Required by
Section 61.207 of 40 CFR Part 61, Subpart R" was for illustration only, although it was chosen to
be representative of values likely to be encountered in these types of tests. It was not intended to
represent a true case; Note that both the mean and standard deviation ,enter into the
determination of the critical value, which is needed for certification of an area of a stack for
removal of phosphogypsum.
Comment 4.c: Since phosphogypsum has a low radioactivity content and the accuracy of
laboratory equipment is not perfect, the way radiation is released (in bursts, not continuously)
may lead to overestimating the radium content of a sample of phosphogypsum. EPA should
clarify the equations used for determining the radium-226 concentration of a phosphogypsum
stack, and revise the methods for determining the sample size and testing needed to demonstrate
that the radium concentration is less than 10 pCi/g. However, EPA has assumed that the number
of disintegrations from a 10 g portion of a 10 pCi sample is enough to justify the assumed
transitions from the mathematically correct binomial distribution the to approximate and thus
somewhat less accurate Gaussian statistics used in the draft of "Statistical Procedures ... ." A
binomial distribution is more appropriate for testing purposes, rather than a Gaussian distribution,
as it measures both mean and variance, and is the appropriate expression for radioactivity release.
A rule should be based on full mathematical rigor: The NESHAP should be revised to permit a
statistical analysis based on either a binomial or Gaussian distribution. (TFI, Simplot)
Response: This comment confuses two separate steps that must be undertaken in characterizing
the radium-226 content of phosphogypsum. The first step to is determine the radium-226 content
of each sample removed from the stack. This requires the use of counting statistics, based on the
Poisson distribution. A separate analysis (or count) must be performed on each sample to
determine its radium-226 concentration. The required procedures are described in Part 61,
Appendix B, Method 114. The techniques described there are standard laboratory procedures for
measuring the levels of radioactivity in samples. Once the radium-226 concentrations of each of
the samples has been determined, the procedures outlined in the revised Section 61.207 of
Subpart R, promulgated with this rulemaking, are used in performing the second step, where the
average radium-226 concentration of the phosphogypsum in the area of the stack is determined.
The second step does not rely on the procedures of Method 114. Instead the statistics outlined in
Section 61.207, and discussed in the document "Statistical Procedures for Certifying
Phosphogypsum for Entry into Commerce, as Required by Section 61.207 of 40 CFR Part 61,
Subpart R" are appropriate.
For example, in a case where 30 samples of phosphogypsum had been removed from a stack
for analysis, the procedures used in Method 114 would be used to determine the, radium-226
concentrations in each of the 30 samples. After these 30 concentrations had been determined, the
radium-226 concentration in the area of the stack from which phosphogypsum is to be removed
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would then be determined following the procedures outlined in Section 61.207 and discussed in
the document "Statistical Procedures for Certifying Phosphogypsum for Entry into Commerce, as
Required by Section 61.207 of 40 CFR Part 61, Subpart R." The procedures outlined there are
based on the normal (or Gaussian) distribution. As discussed in the Appendix of this document,
there is good theoretical justification for the use of this distribution
Comment 4.d: For the sampling protocol, EPA should consider a method that would take known
characteristics of a particular phosphogypsum source into account and allow the mean value of a
certain number of samples to be used as a qualifying limit, since the risk associated with radium
content does not vary that much within a few pCi/g of EPA's limit of 10 pCi/g. The closer the
radium content is to 10 pCi/g, the more samples are required to determine the actual radium
content within EPA's error band, and there will always be a risk of misclassification. (Chambers)
Response: The test that the Agency is requiring for demonstrating that the phosphogypsum
which is to be removed from a stack is no greater than 10 pCi/g is based on the standard statistical
test of hypotheses. The test is conservative. It is structured in such a way that strong evidence is
required in demonstrating that the true concentration is less than 10 pCi/g. In cases where the
true mean is less than 10 pCi/g, the closer the true mean is to 10 pCi/g, the more demanding the
evidence required (i.e. the larger the sample needed to demonstrate compliance). This is
appropriate, because the Agency's concern is the risk posed by the use (or misuse) of
phosphogypsum.
Comment 4.f: The value of 0.05 in the proposed rule is the probability that sampling the stratum
of phosphogypsum entering commerce shows that it is safe to distribute/transport the
phosphogypsum when it is not in fact safe to do so - that is, when the true sampling value exceeds
10 pCi/g. This type of analysis will result in phosphogypsum being rejected for use when it
should be accepted. This false rejection rate could be excessively high, depending on the mean
radium content of the phosphogypsum. The revised rule should adopt a balance between
allowable Type I and Type II errors. (Simplot)
Response: There is always a chance of occurrence a Type 1 or a Type II error in tests of
statistical hypotheses, such as the test required by Section 61.207. The chance of error is inherent
in all tests of hypotheses. In structuring these tests, there is a tradeoff in the chances of Type I
and Type II errors. Given no change in the sample size, the consequence of reducing the chance
of occurrence of a Type I error is to increase the chance of occurrence of a.Type II error.
Similarly, an attempt to reduce the chance of a Type II error will result in an increase in the
chance of a Type I error. An increase in the sample size, with no other changes in the test, is the
only way to simultaneously reduce the chance of occurrence of both the Type I and Type II
errors. The Agency's choice of a .05 probability of occurrence of a Type I error is predicated on
the need to protect the general public from the risk of radiation exposure.
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