EPA Review of Standards for Uranium and Thorium Milling Facilities @ 40 CFR Parts 

61 and 192.

Comments by Steven H Brown, CHP

Revised November 7, 2010

I am Steven Brown from Centennial Colorado. I appreciate the opportunity to provide these 

comments for EPA’s consideration regards to review of EPA standards for Uranium and 

Thorium Milling Facilities @ 40 CFR Parts 61 and 192.

I have been a practicing health physicist for over 40 years. I am certified by the American 

Board of Health Physics and a Diplomat of the American Academy of Health Physics. I am a 

past president of Central Rocky Mountain Chapter of the Health Physics Society.

The Health Physics Society, formed in 1956, is a scientific organization of professionals 

who specialize in radiation safety. Its mission is to support its members in the practice of 

their profession and to promote excellence in the science and practice of radiation safety. 

Today its nearly 6,000 members represent all scientific and technical areas related to 

radiation safety including academia, government, medicine, research and development, 

analytical services, consulting, and industry in all 50 states and the District of Columbia. 

I would like to provide EPA with some broad scientific perspectives related to the adequacy 

of existing public exposure standards for uranium mills and in situ recovery facilities that 

are promulgated in 40 CFR Parts 61, 190 and 192. Specifically, these are the 20 picocuries 

per meter squared per second (pCi / m2‐sec) radon flux criteria for uranium mill tailings 

impoundments specified in Part 61 Subpart W and Part 192, Subpart D as well as the 25 

mrem /year public exposure standard in Part 190 as referenced in Part 192. 
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My remarks will address the following seven questions:

1. Are the existing radiation dose limits in the regulations (Federal and Agreement 

States) for uranium milling facilities (including in situ recovery plants) adequate to 

protect the public from additional radiation exposure above our natural background 

exposure?

2. Is the existing 20 picocuries per meter squared per second (pCi/meter2 – sec) radon 

flux (emission) standard in 40 CFR Parts 61, Subpart W and 192, Subpart D 

adequate to protect the public from additional radiation exposure above our natural 

background exposure?

3. What do we know about radon releases from water impoundments?

4. What do we know about radon emissions from ISRs?

5. What are current practices and results in estimating doses to the public from 

uranium recovery facilities?

6. What is known about the potential health effects to populations living in the vicinity 

of uranium mines and mills?

7. What is known about the health impacts (e.g., lung cancer) to many uranium miners 

who worked underground in the 1950s and 1960s?

1. Are the existing regulations (Federal or USNRC Agreement States) for uranium 

milling facilities (including in situ recovery plants) adequate to protect the public 

from additional radiation exposure above our natural background exposure?

Our lifestyles, where we choose to live, what we eat and drink, has a much larger impact on 

our  radiation  exposure  than  exposure  at  current  regulatory  limits.  The  basic  regulatory 

limits that operating uranium mills and ISRs must comply with are 100 millirem* per year 

from  all  sources  including  radon  and  25  millirem  /  year  excluding  radon**  (US  Nuclear 

Regulatory  Commission:  10  CFR  20  and  10  CFR  40  Appendix  A;  US  Environmental 

Protection Agency: 40 CFR 190; Texas Department of State Health Services, Title 30 of the 

Texas  Administrative  Code,  Chapter  336;  Colorado  Department  Health  of  Public  and 

Environment, 6 CCR 1007 ‐ 1, Part 4)

*NOTE: a millirem is a unit of effective radiation dose. It is related to the amount of energy absorbed by 

human tissue and other factors. 1,000 millirem = one rem.

** Radon is a naturally occurring radioactive gas, which is released into the atmosphere at the Earth’s surface 

from the decay of radium. Both radium and radon are daughter products of uranium.

Now lets compare these numbers to the annual radiation doses we receive as citizens of 

planet Earth. Figure 1 below depicts the typical components of human exposure in the US

to ionizing radiation.
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Figure 1:  Percent contribution of various sources of exposure to the total radiation dose of a typical 

resident in the US. Reproduced from National Council on Radiation Protection and Measurements.  

Report No. 160, Ionizing Radiation Exposure of the Population in the United States. 2009.

                                                                                                                                                                                                             

As can be seen from figure 1, background radiation exposure is about 50% of the total 

exposure; the other 50% is primarily from medical exposures. Consumer products we use 

everyday that contain radioactive materials (e.g., smoke detectors, luminous watches, etc) 

contribute about 2 % of our dose. Other man made sources of radiation, including the 

nuclear industry, contribute < 0.1% of our annual dose.

Natural background can vary considerable from place to place across the United States or 

over relatively small areas within a region. This is due to effects of elevation (higher cosmic 

radiation exposure at higher elevations), greater levels of naturally occurring radioactive 

elements in soil and water in mineralized areas (e.g., igneous formations in Rocky 

Mountains) and other factors like local geology and chemistry. This is depicted in Table 1, 

which compares average annual background radiation exposure for the US, all of Colorado 

and Leadville, CO. (high elevation and in mineralized area) as contrasted to coastal areas 

like Virginia and Oregon.  This table shows the major components of natural background 

radiation including terrestrial radiation (uranium, radium, thorium and a naturally 

radioactive form of potassium in soil, rocks and water), cosmic radiation (high energy 

particles and rays from space) and internal radiation (from food, water and radon gas from 
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natural uranium decaying in the ground).

The data in Table 1 demonstrates that the differences in annual background exposure 

based on where one chooses to live, what one chooses to eat and drink have a much greater 

impact on public exposure than the regulatory dose limits we discussed above. 

Source US Avg.1 Colorado 2 Leadville, 

CO. 2

Virginia 3 Oregon 3

Cosmic 

Radiation

     31 50 85 28 28

Terrestrial 

Radiation

     19 49 97 20 27

Radon and 

Other Internal

  260 301 344 182 102

Totals     310 400 526 230 157

TABLE 1: Comparison of average radiation backgrounds in US  (units of millirem / yr)

1 National Council on Radiation Protection and Measurements.  Report No. 160, Ionizing Radiation Exposure of 

the Population in the United States. 2009. 2 Moeller D, Sun LSC. Comparison of Natural Background Dose Rates for Residents of the Amargosa Valley, NV, 

to those in Leadville, CO, and the States of Colorado and Nevada. Health Physics 91:338‐353; 2006 3 USEPA.  Assessment of Variations in Radiation Exposure in the United States.  Contract Number EP‐D‐05‐

002 (Revision 1).  Washington, DC.  2006

Because background radiation varies significantly across the U.S., it follows that population 

exposure varies accordingly. As indicated in Table 1, if for example, one chooses to live in 

Colorado vs. Oregon, the difference in his or her annual radiation dose is more than 240

mrem /yr which is more than twice the Federal public exposure limit for uranium mills of 

100 mrem /yr. In other words, if you are a resident of Colorado and leave to visit your 

sister for a month in Oregon, you could “save” 20 – 30 mrem of exposure, which is about 

equal to the EPA 40 CFR 190 limit of 25 mrem /year excluding radon.

2. Is the existing 20 picocurie/meter2 – second (pCi/m2­sec) radon flux /emission 

standard in 40 CFR Parts 61, Subpart W and 192, Subpart D adequate to protect the 

public from additional radiation exposure above our natural background exposure ?

Specifically regarding natural background exposure to radon, note that Figure 1 and Table 

1 demonstrate that radon can contribute much more than 50 % of our total background 

exposure and almost 300 mrem / yr in the Rocky Mountain States (due to higher levels of 

natural uranium and radium in the soil and rocks than, e.g., the coastal plains of the US). 

It is recognized that EPA’s public exposure criteria for radon in 40 CFR 61, Subpart W and 

Part 192, Subpart D is expressed as a “flux” (emission rate from a surface) of 20 pCi/m2‐
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sec. This limit however includes natural background, which is typically 1‐2 pCi/m2‐sec 

almost anywhere on the earth’s surface and can be several times higher than this in 

mineralized areas. So in some places, the EPA radon flux limit could be just a few times the 

existing background rate. 

It is also recognized that 40 CFR Subpart W also imposes work practice requirements @ 

61.252(b)(1) limiting the operator to two tailings impoundments of no more than 40 acres 

each. Accordingly, if it is assumed that the entire 80‐ acres are emitting radon at the limit of 

20pCi/m2 ‐sec, the annual “source term” can be directly calculated to be about 200 Curies. 

This is approximately equal to the “source term” from 2‐3 square miles of the earth, almost 

anywhere, at a typical planet wide background flux of 1 ‐ 2 pCi/m2‐ sec.

However, the quantity or emission rate of a radionuclide from a source within the 

restricted area of a licensed facility is not the primary criteria for public radiation 

protection. This is routinely achieved by demonstrating compliance with the fundamental 

public dose limit of 100 mrem /year including radon (e.g., @ 10 CFR 20.1301 and 

commensurate sections of Agreement State regulations) and in demonstrating compliance 

to concentrations of radionuclides permitted to be released to unrestricted areas (e.g., at 

the site boundary) specified in 10 CFR 20, Appendix B, Table 2 (for radon = 1 X 10‐8 uCi/ml 

w/o progeny; 1 X 10‐10 with progeny). 

It is at the site boundary and/or locations where people actually live, not at a somewhat 

arbitrary* location within the restricted area inaccessible to the public, that public 

radiation protection criteria should be applied. Although the historical need is understood 

for establishment of the radon flux criteria to limit radiological impact to a future public 

who may have access to formerly decommissioned uranium tailings sites, for licensed 

operating facilities, other mature regulatory controls as referenced here provide much 

greater assurances that exposure of the public is maintained ALARA in support of 

optimizing the risk vs. benefit relationship.

* “Arbitrary” relative to the most likely pathways of exposure to a member of the pubic including 

considerations of local meteorology and demography

3. What Do We Know About Radon Releases from Water Impoundments?

In response to concerns regards to radon releases from the decay of its radium parent 

contained in water impoundments (e.g., evaporation ponds) associated with uranium 

recovery facilities, two recent reports provide some valuable insight:

(1) SENES Consultants Ltd, Evaporation Pond Radon Flux Analysis, Piñon Ridge Mill Project, 

Montrose County, Colorado. August 2010 for Energy Fuels Resources Corporation; included 

as Appendix D of Energy Fuels’ Application for Approval for Construction, Pinon Ridge Mill, 

Montrose County, Colorado as submitted to US EPA Region VIII, Denver, Colorado August 31 

2010. This report is posted along with the complete application on the EPA Subpart W web 
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site under “Applications”, Pinon Ridge Mill: Application for Approval of Construction of 

Tailings Facility.

This study provided estimates of radon flux from and concentrations above proposed 

water impoundments (evaporation ponds containing raffinate solution) with a specified 

radium concentration and compared results to other existing models. Conservative 

estimates of radon flux indicates that the emissions are low and less than or similar to the 

pre‐operational average background radon flux of 1.7 pCi m‐2 s‐1 observed at various 

locations within the proposed tailings areas on the site.  The estimated radon flux levels 

from the evaporation ponds is also a small fraction (less than 10%) of the 20 pCi m‐2 s‐1

limit for pre‐1989 uranium tailings that has been assumed here for context.  This 

conservative estimate was based on the Nielson and Rogers model *.  

* Nielson, K.K. and V.C. Rogers 1986.  Surface Water Hydrology Considerations in Predicting Radon Releases 

from Water­Covered Areas of Uranium Tailings Ponds.  Proc. Eighth Annual Symposium on Geotechnical & 

Hydrological Aspects of Waste Management, Geotechnical Engineering Program, Colorado State University & 

A.A. Balkema, Fort Collins, CO, USA, February 507, PP:215‐222.

The model assumes that the emission rates are enhanced by the turbulence at the top layer 

of the water column where all the radon in the top one‐meter of water is assumed to be 

released to air instantaneously.  For comparison purposes, the same parameters were used 

to estimate the radon emissions using an on‐line program that is available on the World 

Information Services on Energy (WISE) website. The on‐line model, which is attributed to 

the Rogers and Nielson model, produced identical results.

The results of this assessment also indicated that the radon emissions associated with the 

evaporation of the raffinate solution and the emissions due to the operation of sprinkler 

systems are extremely low and insignificant compared to the radon flux from the ponds

due  to diffusional and turbulence processes.

Finally, the calculations indicated that the incremental air concentration due to the 

emission of radon from the evaporation ponds is very small (on the order of 3%) relative to 

the assumed background radon concentration.

(2) K.R. Baker and A.D. Cox 2010.  Radon Flux from Evaporation Ponds.  Presented at 

National Mining Association (NMA) / Nuclear Regulatory Commission (NRC) Uranium 

Recovery Workshop 2010, Denver, CO, May 26‐27.

A presentation by Baker and Cox at the most recent NMA/NRC workshop in Denver (May 

2010) and subsequently at the National Health Physics Society Annual Meeting in Salt Lake 

City (June 2010) considers the situation where appreciable concentrations of radon are 

present in the ponded water, as may arise for example from elevated levels of Ra‐226 

dissolved in the pond water.  Baker and Cox, reporting on a stagnant film model and some
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measurement data*, suggest a radon flux of the order of 1 pCi m‐2 s‐1 per 100 pCi/L of 

dissolved radon in the ponded water. 

* A modified version of EPA Method 115 was used to measure radon flux from the pond surface

4. What do we know About Radon Emissions from ISRs?

Regarding radon evolution from in situ uranium recovery facilities, the majority of radon, 

which is released at the surface is not (as at a conventional mill) a result of on‐surface 

decay of radium over time in tailings impoundments since ISRs do not generated 

conventional tailings as a radon source. At ISRs, the radon is brought to the surface 

dynamically, dissolved in the lixiviant returning from underground. Just as dynamically, 

that portion of the total dissolved radon that is above the solution's saturation value is 

released when encountering atmospheric pressures and temperatures. 

Modern ISR uranium recovery processes are operated under “closed loop’ conditions. The 

circulating lixiviant goes directly from well field header houses thru the ion exchange 

process and is then reconstituted and returned directly to the well field as an essentially 

closed system. Atmospheric conditions are initially encountered during resin transfer at 

the shaker screens. Accordingly, the vast majority of the “radon source term” for these 

facilities is associated with small releases from the well heads and header houses in the 

well fields and from the IX ‐ resin – elution system interface where the process is first 

opened to atmospheric pressure. For facilities that have water retention ponds at the back 

end of the process (barren lixiviant bleeds, restoration wastes, etc), only a small percentage 

of the radon originally dissolved in the pregnant lixiviant initially returning from the well 

fields would be expected to remain. ISRs in Texas are currently operating without these 

“surge ponds” and send liquid wastes directly to a permitted deep disposal well.*

* For general discussions of the radiological characteristics of ISRs, including mechanisms of radon evolution, 

see: National Mining Association. Generic Environmental Report in Support of the Nuclear Regulatory 

Commission’s Generic Environmental Impact Statement for In Situ Uranium Recovery Facilities, K Sweeney, 

NMA to L Camper, USNRC November 30, 2007; Brown, S. The New Generation of Uranium In Situ Recovery 

Facilities: Design Improvements Should Reduce Radiological Impacts Relative to First Generation Uranium 

Solution Mining Plants. Proceedings of the 2008 Waste Management Symposium, Phoenix. ASME Press, New 

York, NY, ISBN # 978160560422. 2008. 

For more on mechanisms of ISR radon source terms see: Brown, S. and Smith, R., 1982. A Model for 

Determining the Radon Loss (Source) Term for a Commercial In Situ Leach Uranium Facility. In: M. Gomez 

(Editor), Radiation Hazards in Mining‐Control, Measurement, and Medical Aspects. Soc. Min. Eng., pp. 794—

800; Marple, M.L and Dziuk, T, Texas Department of Health, Bureau of Radiation Control. Radon Source Terms 

at In Situ Uranium Extraction Facilities in Texas. Proceedings of the Sixth Annual Uranium Seminar, South 

Texas Minerals Section of AIME. Corpus Christi. September 11‐14, 1982
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5. What are Current Practices and Results in Estimating Doses to the Public from 

Uranium Recovery Facilities?

Calculations performed in accordance with existing NRC guidance are used to estimate 

source terms and calculate off‐site dose to the public. For example, USNRC Regulatory 

Guide 3.59, Section 2.6 provides methods acceptable to NRC for estimating the radon 

source term during ISR operations. Additionally, USNRC NUREG 1569, Appendix D, 

provides the MILDOS – AREA computer code methodology acceptable to the NRC, which 

includes expressions for calculating the annual Rn‐222 source terms from various aspects 

of ISR operations which is then used by MILDOS to calculate off‐site public dose and 

demonstrate compliance with dose limits of 10 CFR 20.1301.

See e.g.: U.S. Nuclear Regulatory Commission, NUREG‐1569, Standard Review Plan for In Situ Leach Uranium 

Extraction License Applications, June 2003. Yuan, Y.C., J.H.C. Wang and A. Zielen. 1989. MILDOS­AREA: An 

Enhanced Version of MILDOS for Large­area Sources. Argonne National Laboratory (ANL) report ANL/ES‐161. 

June 1989; U.S. Nuclear Regulatory Commission (NRC), 1987. Methods for Estimating Radioactive and Toxic 

Airborne Source Terms for Uranium Milling Operations. Regulatory Guide 3.59.

Regards to historical estimates of offsite radon concentrations and public dose from ISRs as 

reported by its licensees, the U.S. Nuclear Regulatory Commission, in NUREG‐1910, Generic 

Environmental Impact Statement for In­Situ Leach Uranium Milling Facilities (2009), 

Chapter 4.2 indicates:

• Quarterly and biannual measurements of downwind concentrations of radon at an 

operational ISR facility boundary from 1991 to early 2007 were below 74 Bq/m3 

[2.0 pCi/liter] with a majority of measurements below 37 Bq/m3 [1 pCi/liter]. For 

comparison, these measured values are well below the NRC effluent limit for radon 

at 10 CFR Part 20, Appendix B of 370 Bq/m3 [10 pCi/liter] and in fact, are probably 

just background values.

• Argonne National Laboratory’s MILDOS‐AREA computer code (Argonne National 

Laboratory, 1989 – see above) is typically used to calculate radiation doses to 

individuals and populations from releases occurring at operating uranium recovery 

facilities. The code is capable of modeling airborne radiological effluent releases 

applicable to both conventional mills and ISR facilities (including radon gas from 

well fields and processing facilities and yellowcake particulates from thermal drying 

operations)

• All reported doses have been well within the 10 CFR Part 20 annual radiation dose 

limit for the public of 1 mSv [100 mrem/yr] including dose from radon and its 

progeny and within the EPA fuel cycle annual limit (40 CFR 190) of 0.25 mSv [25 

mrem], which does not include dose due to radon and its progeny. 
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6. What is known about the potential health effects to populations living in the 

vicinity of uranium mines and mills?

Uranium is a heavy metal and acts similarly to other heavy metals in the body (like 

molybdenum, lead, mercury). Accordingly, for natural uranium, national and international 

human exposure standards are based on the possible chemical toxicity of uranium (e.g., 

effect on kidney—nephrotoxicity), not on radiation and possible “cancer effects” 

(radiotoxicity). However, there has never been a death or permanent injury to a human 

from uranium poisoning*.

* See e.g.: (1) U.S. Nuclear Regulatory Commission. Standards for Protection Against Radiation; 10 CFR 20, 

Appendix B., Table 1. 1992. (2) International Commission on Radiological Protection. Limits for Intakes of 

Radionuclides by Workers. ICRP Publication 30, 1979.  (3) US Dept. of Health and Human Services, Public 

Health Service, Agency for Toxic Substances and Disease Registry. Toxicological Profile for Uranium. 1999. 

(4) Acute Chemical Toxicity of Uranium. Kathryn, RL and Burkin, RK. Health Physics, 94(2), pp 170‐179, 

February 2008)

Regarding ionizing radiation in general, the health effects are well understood. No health 

effects have been observed in human populations at the exposure levels within the range 

and variability of natural background exposures in the US. An official position of the 

National Health Physics Society is that below 5,000 – 10,000 millirem  (which includes the 

range of both occupational and environmental exposures), risks of health effects are either 

to small to be observed or non‐ existent (see Radiation Risks in Perspective

@hps.org/hpspublications/positionstatements). International and national authorities that 

establish exposure standards for workers and the public rely on the work of scientific 

committees of the highest professional standing for their evaluations of the scientific 

information on the health effects of ionizing radiation. These scientific committees include 

the United Nations Scientific Committee on the Effects of Ionizing Radiation (UNSCEAR); 

the International Commission on Radiological Protection (ICRP); the National Academy of 

Science’s Biological Effects of Ionizing Radiation (BEIR) Committee, the National Council on 

Radiation Protection and Measurements (NCRP) and others.

But what about the specific concerns regarding health effects to populations living close to 

uranium recovery facilities? Despite much confusion and misunderstanding, possible 

health effects in populations living near uranium mines and mills have been well studied. 

No additional effects have been observed when compared to the health status of other 

similar populations not living nearby. A few sources providing the scientific evidence that 

supports this conclusion include:

• US Department of Health and Human Services, Public Health Services, Agency for 

Toxic Substance and Disease Registry, Toxicological Profile for Uranium, 1999. 

Chapter 1: Public Health Statement for Uranium, Section 1.5: How Can Uranium 

Effect My Health? – “ No human cancer of any type has ever been seen as a result of 

exposure to natural or depleted uranium” (Available at: 
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http://www.atsdr.cdc.gov/toxprofiles/tp150.html)

• Cancer and Noncancer Mortality in Populations Living Near Uranium and Vanadium 

Mining and Milling Operations in Montrose County, Colorado, 1950 ­2000. Boice, JD, 

Mumma, MT et al. International Epidemiology Institute, Rockville, MD and 

Vanderbilt University, Vanderbilt‐Ingram Cancer Center, Nashville, TN. Journal of 

Radiation Research, 167:711‐726; 2007: “ The absence of elevated mortality rates of 

cancer in Montrose County over a period of 51 years suggests that the historical 

milling and mining operations did not adversely affect the health of Montrose 

County residents”

• Cancer Mortality in a Texas County with Prior Uranium Mining and Milling Activities, 

1950 – 2001. Boice, JD, Mumma, M et al. International Epidemiology Institute, 

Rockville, MD and Vanderbilt University, Vanderbilt‐Ingram Cancer Center,

Nashville, TN Journal of Radiological Protection, 23:247 – 262; 2003 – “No unusual 

patterns of cancer mortality could be seen in Karnes County over a period of 50 

years suggesting that the uranium mining and milling operations had not increased 

cancer rates among residents”.

• Cancer Incidence and Mortality in Populations Living Near Uranium Milling

and Mining Operations in Grants, New Mexico, 1950–2004. Boice, JD, Mumma, M et al.

International Epidemiology Institute, Rockville, MD and Vanderbilt University, 

Vanderbilt‐Ingram Cancer Center, Nashville, TN. Journal of Radiation Research, 174, 

624–636. 2010 – “With the exception of male lung cancer (in former underground 

miners), this study provides no clear or consistent evidence that the operation of 

uranium mills and mines adversely affected cancer incidence or mortality of county

residents”.

7. But what about the known health impacts (e.g., lung cancer) to many uranium 

miners who worked underground in the 1950s and 1960s? 

These miners worked in conditions that by today’s standards we would consider 

unacceptable. They were exposed to very high levels of radon progeny (which are decay 

products of uranium) in poorly ventilated underground mines. Many of these miners also 

had severe smoking habits, which enhanced the ability of the radon daughters to deliver 

radiation dose to the lung. Follow up of 68,000 former miners over many years indicated 

the occurrence of about 2700 lung cancers in this population; much higher than the

expected incidence. This is an incidence rate of about 4%. As a point of comparison, the 

baseline incident rate of lung cancer in non‐smoker, Caucasian males today is about 0.4 % 

(Dr. John Boice, International Epidemiology Institute, Vanderbilt University – personal 

communication)

These conditions existed before we had Federal Agencies (Occupational Safety and Health 
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Administration ‐ OSHA, Mine Safety and Health Administration ‐ MSHA, US Nuclear 

Regulatory Commission ‐ NRC) and laws to better protect workers throughout American 

industry (construction, manufacturing, farming, mining, etc). Based on the best scientific 

information available, we consider as safe the occupational exposure standards we have 

today as enforced by these agencies. The level of exposure of some of these early uranium 

miners was 100 – 1000 times higher than our current Federal standards.

As just one of many possible historical comparisons regards to working conditions in 

American industry decades ago, it is of note that almost 100 men died from construction 

and related accidents in the building of the Hoover Dam in the 1920s, long before Federal 

regulations were in place to protect workers. These circumstances would of course also be 

unacceptable today

Conclusions:

(1) The existing public radiation exposure criteria for uranium mills and in situ recovery 

facilities in 40 CFR Parts 61, 190 and 192 are adequately protective since they represent 

small fractions of the natural radiation background variation across the US. Our lifestyles, 

where we choose to live, what we eat and drink, has a much larger impact on our radiation

exposure than exposure at these very low regulatory limits.

(2) Regarding ionizing radiation in general, the health effects are well understood. No 

health effects have been observed in human populations at the exposure levels within the 

range and variability of natural background exposures in the US.

(3) Radon emission rates ( flux) from water impoundments (evaporation ponds) at 

licensed conventional mills and ISRs are not expected to be significantly different than that 

from typical background radon emission associated with land surfaces almost anywhere 

due to the very poor diffusion of radon through water.

(4) Historical environmental measurements made in the vicinity of uranium recovery 

facilities and public dose assessment performed and reported to the USNRC indicate radon 

concentrations at site boundary locations and doses to the public are consistently well 

below Federal limits.

(5) The possibility of health effects in populations living near uranium mines and mills over 

50 years have been well studied by national scientific bodies of the highest professional 

standing. No additional effects have been observed when compared to the health status of 

other similar populations not living nearby.

(6) However, given that 40 CFR 192 was released in 1983, changes and updates have been 

made in the basic dosimetry models and science we use today to estimate radiological 

doses and risks. Accordingly, EPA should consider reassessing exposure terminology and 

criteria (e.g., as used in 40 CFR 190) to be consistent with current national and 

international methods and models, e.g., (1) International Commission on Radiological 
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Protection, 2008. “Publication 103 Recommendations of the ICRP, Annals of the ICRP.”

2008 and (2) National Research Council, 2006. “Health Risks for Exposure to Low Levels of 

Ionizing Radiation; BEIR VII, Phase II.”