Uranium Toxicity
(last updated 7 Dec 2016)
Contents:
> See also:
Uranium presents both chemical and radiological hazards. Risk assessments must address both types of hazards, therefore.
Unfortunately, there are some problems with the comparison of these hazards:
- insufficient data for chemical toxicity:
there is no data available for long-term effects of uranium ingestion on humans, all information available is from intermediate-term studies on animals,
- standards for radiation doses and chemical toxicity not comparable:
for radiation and for cancer-inducing effects of chemical toxics, a linear dose-effect relationship is assumed at low doses and low dose rates; therefore any standard can only limit the effects to a selected level, while for non-cancer-inducing effects of chemical toxics, the existence of a no-adverse-effect level is assumed.
- residual risk from chemical toxicity regarded acceptable usually is orders of magnitude lower than from radiation:
the lifetime cancer risk from continuous radiation exposure at ICRP's dose rate standard for the public of 1 mSv/a during a 70 year lifetime is 1 : 286, and the lifetime cancer risk for workers exposed at ICRP's current dose rate standard for workers of 20 mSv/a during a 40 year work life is 1 : 31, while the acceptable lifetime risk from toxics often is selected in the 1 : 10,000 to 1 : 1,000,000 range.
(see also: Uranium Biokinetics Calculator)
The study [ATSDR1999] reviews all published data on animal studies known on uranium toxicity:
- For the hazard from intermediate duration inhalation of soluble forms of uranium, the study [Rothstein1949a] on dogs, is used: It showed that uranium concentrations of 0.15 mg U/m3 in air produced the lowest observable adverse effect. From this figure, a "minimal risk" inhalation level for humans of 0.4 µg/m3 is derived, applying a number of safety factors.
- For the hazard from intermediate duration inhalation of insoluble forms of uranium, the study [Rothstein1949b] on dogs, is used: It showed that uranium concentrations of 1.1 mg U/m3 in air produced no observable adverse effect. From this figure, a "minimal risk" inhalation level for humans of 8 µg/m3 is derived, applying a number of safety factors.
- For the hazard from chronic duration inhalation of soluble forms of uranium, the study [Stokinger1953b] on dogs, is used: It showed that uranium concentrations of 0.05 mg U/m3 in air produced no observable adverse effect. From this figure, a "minimal risk" inhalation level for humans of 0.3 µg/m3 is derived, applying a number of safety factors.
In another review [Jacob1997], performed for the German Federal Environmental Agency, another study performed by [Stokinger1953a] on rats is used: The rat study showed slight impacts to the kidneys at uranium resorption rates of 2.6 µg per kg per day. This rate corresponds to uranium concentrations of 40 µg per m3 in air. Applying a number of safety and conversion factors, the authors obtain a "tolerable" level of 0.07 µg/m3 uranium in air.
Inhalation of uranium
(based on chemical toxicity)
| TAC
[µg/m3] |
| [ATSDR1999] intermediate duration, soluble | 0.4 |
| [ATSDR1999] intermediate duration, insoluble | 8 |
| [ATSDR1999] chronic, soluble | 0.3 |
| [Jacob1997] | 0.07 |
TAC = Tolerable Air Concentration
(see also Uranium Radiation Exposure · Uranium Radiation Individual Dose Calculator)
Inhalation of uranium for workers
(based on radiological hazard)
| | insoluble | |
soluble |
|---|
| |
Dose fact.
[mSv/mg] | ALI
[mg] | DAC
[µg/m3] | |
Dose fact.
[mSv/mg] | ALI
[mg] | DAC
[µg/m3] |
| natural uranium with all progeny in secular equilibrium | |
0.42 | 47.6 | 16.5 | |
0.34 | 59 | 21 |
| pure natural uranium | |
0.2 | 100 | 34.7 | |
0.013 | 1520 | 530 |
| enriched natural uranium (3.5%) | |
0.676 | 29.6 | 10.3 | |
0.044 | 450 | 159 |
| depleted natural uranium (0.2%) | |
0.110 | 183 | 63.4 | |
0.0073 | 2740 | 950 |
| recycled uranium | |
0.65 | 31 | 10.8 | |
0.041 | 486 | 169 |
| enriched recycled uranium (3.5% equiv.) | |
2.80 | 7.15 | 2.5 | |
0.176 | 114 | 39 |
| depleted recycled uranium (0.2%) | |
0.173 | 116 | 40 | |
0.011 | 1750 | 610 |
ALI = Annual Limit on Intake based on 20 mSv/a
DAC = Derived Air Concentration based on 20 mSv/a, breathing rate of 1.6 m3/h, working time of 1800 h/a
Short-lived decay products included
Based on ICRP68 dose factors for 1 µm AMAD, initial enrichment to 3.5%, burnup of 39 GWd/tHM, storage time of 5 years after unload
Inhalation of uranium for the public
(based on radiological hazard)
| | insoluble | |
soluble |
|---|
| |
Dose factor
[mSv/mg] | ALI
[mg] | DAC
[µg/m3] | |
Dose factor
[mSv/mg] | ALI
[mg] | DAC
[µg/m3] |
| natural uranium with all progeny in secular equilibrium | |
0.70 | 1.42 | 0.18 | |
1.6 | 0.63 | 0.08 |
| pure natural uranium | |
0.22 | 4.5 | 0.58 | |
0.013 | 74.5 | 9.4 |
| enriched natural uranium (3.5%) | |
0.75 | 1.34 | 0.17 | |
0.045 | 22.3 | 2.8 |
| depleted natural uranium (0.2%) | |
0.12 | 8.3 | 1.05 | |
0.0075 | 134 | 17 |
| recycled uranium | |
0.71 | 1.41 | 0.18 | |
0.081 | 12.3 | 1.6 |
| enriched recycled uranium (3.5% equiv.) | |
3.1 | 0.324 | 0.041 | |
0.4 | 2.49 | 0.32 |
| depleted recycled uranium (0.2%) | |
0.19 | 5.27 | 0.67 | |
0.012 | 85.1 | 11 |
ALI = Annual Limit on Intake based on 1 mSv/a
DAC = Derived Air Concentration based on 1 mSv/a, breathing rate of 0.9 m3/h, continuous exposure
Short-lived decay products included
Based on ICRP72 dose factors for adults, initial enrichment to 3.5%, burnup of 39 GWd/tHM, storage time of 5 years after unload
Note:
The ICRP68/ICRP72 
(1995/1997) dose factors used here show significant differences from those in ICRP60/61 (1990): The new inhalation dose factors for uranium and thorium are about a factor of 4 lower, and for actinium a factor 2 lower.
(The dose coefficients for workers were again revised in ICRP137/141 (2017/2019).)
- U.S. NRC Occupational Annual Limits on Intake (ALI's) for Inhalation
- Unatural (soluble): 1 µCi (= 37000 Bq, equiv. to 1.5 g)
Unatural (insoluble): 0.05 µCi (= 1850 Bq, equiv. to 74 mg)
(10 CFR 20, App. B 
, 1991)
These values are based on a committed effective dose equivalent of 5 rems (50 mSv).
- U.S. NRC Occupational Derived Air Concentrations (DAC's)
- Unatural (soluble): 5.0E-10 µCi per ml of air (= 18.5 Bq/m3, equiv. to 0.74 mg/m3)
But, to address the chemical toxicity, the following tighter criterion is defined, in addition to the radiological one:
- 0.2 mg uranium/m3 of air (for soluble uranium)
- 0.045 mg natural uranium/m3 of air, if its decay products are present in equilibrium, as in ore dust prior to chemical separation of the uranium from the ore
Unatural (insoluble): 2.0E-11 µCi per ml (= 0.74 Bq/m3, equiv. to 29.5 µg/m3)
(10 CFR 20, App. B , 1991)
- U.S. Occupational Safety and Health Administration (OSHA) regulations
- Permissible Exposure Limit - Time Weighted Average:
soluble uranium: 0.05 mg/m3
insoluble uranium: 0.25 mg/m3 (!)
(29 CFR 1910 Subpart Z Table Z-1 , 1997)
(see also: Uranium Biokinetics Calculator)
The "minimal risk" level for intermediate-duration ingestion proposed by [ATSDR1999] is an oral uptake of 2 µg of uranium per kg body weight per day. This is based on adverse effects observed by [Gilman1998b] with rabbits at uptakes of 0.05 mg per kg per day.
[Jacob1997] proposes a "tolerable" uptake of 0.7 µg per kg per day. This value is based on adverse effects observed by [McDonald-Taylor1992] with kidneys of rabbits at resorption rates of 3.2 µg U per kg and day.
The World Health Organization (WHO) has established a Tolerable Daily Intake (TDI) for uranium of 0.6 µg/kg body weight per day [WHO1998, WHO2003]. This is based on adverse effects observed by [Gilman1998a] with kidneys of rats at uptakes of 60 µg U per kg per day.
With [Zamora1998], for the first time, a study on the effects of chronic ingestion of uranium with drinking water on humans is available. It finds that kidney function is affected by uranium uptakes considered safe in the publications based on animal studies:
"A study was conducted of the chemical effects on the human kidney
induced by the chronic ingestion of uranium in drinking water. Subjects
were divided into two groups: The low-exposure group, whose drinking
water was obtained from a municipal water system and contained < 1
µg uranium/L, and the high-exposure group, whose drinking water
was obtained from private drilled wells and contained uranium levels
that varied from 2 to 781 µg/L." These levels caused uranium intakes in the range of 0.004 to 9 µg per kg body weight and day.
From the study's conclusions:
" The present investigation suggests that long-term ingestion of uranium by humans may produce interference with kidney function at the elevated levels of uranium found in some groundwater supplies."
"These observed effects may represent a manifestation of subclinical toxicity which will not necessarily lead to kidney failure or overt illness. It may, however, be the first step in a spectrum which with the chronic intake of elevated levels of uranium may lead to progressive or irreversible renal injury."
In a more recent larger study on humans [Kurttio2002], nephrotoxic effects of uranium in drinking water were found even for low concentrations - without a clear threshold. The authors conclude that "... our results suggest that the safe concentration of uranium in drinking water may be within the range of proposed guideline values of 2-30 µg/L".
In another study with people who consumed drinking water with elevated uranium concentrations [Kurttio2005], the same authors found some indication that, in addition to kidneys, bone may be another target of chemical toxicity of uranium in humans.
Based on the higher uranium resorption in humans rather than experimental animals, [Konietzka2005] assumes a Tolerable Daily Intake of 0.2 µg/kg body weight per day and recommends a safe concentration in drinking water of 10 µg/L for lifetime exposure.
Ingestion of uranium
(based on chemical toxicity)
| TDI
[µg/(kg·d)] | ALI
[mg] | DDWC
[µg/l] |
| [ATSDR1999] | 2 | 51.2 | 102 |
| [Jacob1997] | 0.7 | 17.9 | 36 |
| [WHO1998] | 0.6 | 15.3 | 31 |
| [Konietzka2005] | 0.2 | 5.1 | 10 |
TDI = Tolerable Daily Intake
ALI = Annual Limit on Intake based on 70 kg body weight
DDWC = Derived Drinking Water Concentration based on 500 l/a
For a discussion of the combined effects of ingested uranium, cyanide, fluoride, and/or nitrate, see [ATSDR2004].
(see also Uranium Radiation Exposure · Uranium Radiation Individual Dose Calculator)
Ingestion of uranium for the public
(based on radiological hazard)
| Dose factor
[mSv/g] | ALI
[mg] | DDWC
[µg/l] |
| natural uranium with all progeny in secular equilibrium | 31.7 | 31.5 | 63 |
| pure natural uranium | 1.23 | 813 | 1630 |
| enriched natural uranium (3.5%) | 3.98 | 251 | 500 |
| depleted natural uranium (0.2%) | 0.71 | 1410 | 2820 |
| recycled uranium | 3.89 | 257 | 515 |
| enriched recycled uranium (3.5% equiv.) |
16.7 | 60 | 120 |
| depleted recycled uranium (0.2%) |
1.08 | 923 | 1850 |
ALI = Annual Limit on Intake based on 1 mSv/a
DDWC = Derived Drinking Water Concentration based on 1 mSv/a, 500 l/a
Short-lived decay products included
Based on ICRP72 dose factors for adults (these don't make a distinction for solubility), initial enrichment to 3.5%, burnup of 39 GWd/tHM, storage time of 5 years after unload
- WHO provisional guideline for drinking-water quality:
- 30 µg of uranium per litre
This value is derived from epidemiological studies on populations exposed to high uranium concentrations and is based on the consumption of 2 litres of drinking water per day [WHO2011].
(see also Issues)
This value supersedes the earlier 2 µg/l provisional guideline, which was based on animal studies and 10% allocation of the TDI to drinking water [WHO1998], the 9 µg/l provisional guideline, which was based on 50% allocation of the TDI to drinking water [WHO2003], and the 15 µg/l provisional guideline, which was based on 80% allocation of the TDI to drinking water [WHO2004].
(see also Issues)
- Health Canada - Interim maximum acceptable concentration (IMAC) for uranium in drinking water:
- 20 µg per litre
(see also Issues)
- U.S. EPA - Rule on Radionuclides in Drinking Water:
- Maximum contaminant level for naturally occuring uranium: 30 µg per litre
EPA determines a safe level of 20 µg/L, assuming that an adult with a body mass of 70 kg drinks 2 liters of water per day and that 80% of exposure to uranium is from water. For cost considerations, however, EPA established a standard of 30 µg/L rather than 20 µg/L.
(65 FR 76707, 7 Dec 2000)
(see also Issues)
- U.S. EPA - Preliminary Remediation Goal (PRG) for Superfund:
- 2.22 µg per litre for U-238 in tap water
(see also Issues)
- U.S. EPA - Groundwater Standards for Remedial Actions at Inactive Uranium Processing Sites:
- Maximum Concentration Limit for combined uranium-234 and uranium-238: 30 pCi/l (1.11 Bq/l)
(Where secular equilibrium obtains, this criterion will be
satisfied by a concentration of 0.044 milligrams per liter
(0.044 mg/l = 44 µg/l). For conditions of other than secular equilibrium,
a corresponding value may be derived and applied, based on the
measured site-specific ratio of the two isotopes of uranium.)
(40 CFR Part 192 (PDF-format); 60 FR 2854, 1995)
- U.S. NRC Occupational Annual Limits on Intake (ALI's) for Oral Ingestion:
- Unatural: 10 µCi (= 14.8 g)
(10 CFR 20, Appendix B , 1991)
- California Public Health Goal for Uranium in Drinking Water (not a regulatory standard):
- 0.5 µg per litre
(Public Health Goal for Uranium in Drinking Water , Office of Environmental Health Hazard Assessment, August 2001 )
- German drinking water standard
- 10 µg per litre
(Trinkwasserverordnung (PDF), view here)
- German standard for bottled water designated suitable for preparation of baby food
- 2 µg per litre
(Mineral- und Tafelwasser-Verordnung (PDF))
- Australian Drinking Water Guidelines:
- the concentration of uranium in drinking water should not exceed 0.02 mg/L (= 20 µg/L)
(ADWG 1996, updated September 2001
)
- Australian and New Zealand Guidelines for Fresh and Marine Water Quality:
- A freshwater low reliability trigger value of 0.5 µg/L was calculated for uranium using an AF (assessment factor) of 20 on limited chronic data. No marine data were available to calculate a guideline value. This should only be used as an indicative interim working level.
(Environment Australia: The National Water Quality Management Strategy (NWQMS) , Vol. 2, Ch. 8, 2000)
- [ATSDR1999] U.S. Agency for Toxic Substances and Disease Registry (ATSDR ): Toxicological Profile for Uranium , September 1999 (see details).
- [ATSDR2004] U.S. Agency for Toxic Substances and Disease Registry:
Interaction Profile for Cyanide, Fluoride, Nitrate, and Uranium , May 2004
- [Gilman1998a] Gilman A P, Villeneuve D C, Secours V E, et al.: Uranyl nitrate: 28-day and 91-day toxicity studies in the Sprague-Dawley rat. Toxicological Sciences Vol.41 No.1 (Jan.), 1998, p.117-128
- [Gilman1998b] Gilman A P, Villeneuve D C, Secours V E, et al.: Uranyl nitrate: 91-day toxicity studies in the New Zealand white rabbit. Toxicological Sciences Vol.41 No.1 (Jan.), 1998, p.129-137
- [Jacob1997] Jacob, P., Pröhl, G., Schneider, K., Voß, J.-U.: Machbarkeitsstudie zur Verknüpfung der Bewertung radiologischer und chemisch-toxischer Wirkungen von Altlasten, Umweltbundesamt , Texte 43/97, Berlin 1997, 145 p.
- [Konietzka2005] Konietzka, R; Dieter, H H; Voss, J-U: Vorschlag für einen gesundheitlichen Leitwert für Uran in Trinkwasser (Proposal for a health based guide value for uranium in drinking water), in: Umweltmedizin in Forschung und Praxis, Vol. 10 (2005), No. 2, p. 133-143
- [Kurttio2002] Kurttio P, Auvinen A, Salonen L, et al.: Renal Effects of Uranium in Drinking Water , Environmental Health Perspectives, Vol. 110, No. 4, April 2002, p. 337-342
- [Kurttio2005] Kurttio P, Komulainen H, Leino A, Salonen L, Auvinen A, and Saha H: Bone as a Possible Target of Chemical Toxicity of Natural Uranium in Drinking Water Environmental Health Perspectives, Vol. 113, No. 1, January 2005, p. 68-72
- [McDonald-Taylor1992] McDonald-Taylor C K, Bhatnagar M K, Gilman A, et al.: Uranyl Nitrate-Induced Glomerular Basement Membrane Alterations In Rabbits: A Quantitative Analysis. in: Bulletin of Environmental Contamination and Toxicology Vol. 48 No.3, 1992, p. 367-373
- [Ortega1989] Ortega A, Domingo J L, Llobet, J M et al.: Evaluation of the oral toxicity of uranium in a 4-week drinking water study in rats. in: Bulletin of Environmental Contamination and Toxicology, Vol.42, No.6, 1989, p. 935-941
- [Rothstein1949a] Rothstein, A: Uranyl Fluoride. in: Voegtlin C, Hodge H C (eds.): Pharmacology and Toxicology of Uranium Compounds I-IV, New York, 1949, p. 548-560
- [Rothstein1949b] Rothstein, A: Uranium Dioxide. in: Voegtlin C, Hodge H C (eds.): Pharmacology and Toxicology of Uranium Compounds I-IV, New York, 1949, p. 614-621
- [Stokinger1953a] Stokinger H E, Baxter R C, Dygert H P, et al.: Chapter 21. Toxicity following inhalation for 1 and 2 years. in: Voegtlin C, Hodge H C (eds.): Pharmacology and Toxicology of Uranium Compounds I-IV, New York, 1953
- [Stokinger1953b] Stokinger H E, et al.: Uranium Tetrachloride. Toxicity following inhalation for 1 and 2 years. in: Voegtlin C, Hodge H C (eds.): Pharmacology and Toxicology of Uranium Compounds I-IV, New York, 1953, p. 1522-1553
- [WHO1998] World Health Organization: Guidelines for Drinking-water Quality, Second edition, Addendum to Volume 2: Health Criteria and Other Supporting Information, WHO/EOS/98.1, Geneva 1998, 283 p.
- [WHO2003] World Health Organization: Guidelines for Drinking Water Quality, Third edition, 2003
- [WHO2004] World Health Organization: WHO Guidelines for drinking-water quality, third edition, 2004 · Uranium in Drinking-water, Background document (172k PDF)
- [WHO2011] World Health Organization: Guidelines for Drinking-water Quality, Fourth Edition, 2011 · Chemical hazards in drinking-water - Uranium
- [Zamora1998] Zamora,M.L., Tracy, B.L., Zielinski, J.M., Meyerhof, D.P. and Moss, M.A.: Chronic Ingestion of Uranium in Drinking Water: A Study of Kidney Bioeffects in Humans, Toxicological Sciences Vol.43, No.1, (May 1998), p. 68-77
- Uranium series ICRP 60/61 dose coefficients (1990)
- Uranium series ICRP 68 dose coefficients for workers (1995)
- Uranium series ICRP 72 dose coefficients for the public (1997)
- Uranium series ICRP 137/141 dose coefficients for workers (2017/2019)
> See also the following review draft reports:
- U.S. ATSDR: Draft Interaction profile for cyanide, fluoride, nitrate, and uranium
(Comments must be received on or before November 30, 2002, see Regulatory Issues)
- U.S. EPA: Comparison of Health Risks Arising From
the Radiological and Chemical Toxicity of Uranium,
Appendix F of Radiation Site Cleanup Regulations: Technical
Support Document For The Development Of Radionuclide Cleanup
Levels For Soil, Review Draft, EPA 402-R-96-011 A,
September 1994.
Download (select file appf.pdf from 1.9M ZIP-archive)
- National Council on Radiation Protection and Measurements : Uranium: Radiation Protection Guidelines, NCRP Draft Report No. SC 57-15, Bethesda MD, August 1999, 145 p.