Table 2 -8. Toxicological Limits on Airborne Concentrations of Transportable (soluble) Uranium

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

Table 2 -8. Toxicological Limits on Airborne Concentrations of Transportable (soluble) Uranium

Chronic Exposure

Occupational Limit, mg/m3

Agency

Reference

NRC

0.2

Footnote to Appendix B, 10

CFR 20 (NRC 1992a)

ACGIH

0.2

Threshold Limit Values and

Biological Exposure Indices for

1997, American Conference of

Governmental Industrial

Hygienists (ACGIH 1997)

OSHA (a)

0.05 (soluble)

29 CFR 1910.1000

0.25 (insoluble)

NIOSH

0.05

National Institute for

Occupational Safety and Health

Preferred/recommended limit.

(a)

Past limits for single acute inhalation intakes have been set by the International Commission on

Radiological Protection in its Publication 6, (ICRP 1964) to 2.5 mg of soluble uranium inhaled in any one

day. This value is based on one day's intake at the maximum permissible concentration (at the time) of 210

g/m3. Lawrence (Lawrence 1984) derived acute inhalation intake limits of 15 and 80 mg for Class D and

Class W materials, respectively. This derivation is based on not exceeding a kidney burden of 3 g U/g

kidney after a single acute inhalation. NRC regulations at 10 CFR 20 limit the intake of soluble uranium to

10 mg in a week.

Chronic exposure to a concentration of 0.2 mg/m3 results in a weekly intake of 9.6 mg (40 h/week x

1.2 m3/h x 0.2 mg/ m3) and a steady-state kidney burden of roughly 900 g, when the ICRP Publication 30

metabolic model for Class D uranium is used. This same model indicates that an acute intake of 18 mg will

result in a prompt kidney burden of approximately 900 g. However, 10 CFR 20 limits acute exposures to

40 DAC-hours, or 9.6 mg.

Recurrent concerns have arisen about the adequacy of existing limits intended to prevent chemical

damage to kidneys. These concerns have focused particularly on the

lack of data on the effects of combined exposures to UO2F2 and HF

lack of detailed information on effects of short-term exposures to soluble/transportable uranium

in the range from 100-1000 mg/m3

lack of data on thresholds for repairable injury.

DOE sponsored research to determine the exposure levels that would be expected to 1) have no

effect, 2) cause non-lethal injury, and 3) be lethal to 50% of the exposed population (LD 50). Researcher

consensus resulted in the uptake levels (in g U/g) listed in Table 2-9 along with the corresponding total

uranium in 70- kg standard man.

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