Hazards and effects of inhaling Uranium

Uranium presents both chemical and radiological hazards. Risk assessments must address both types of hazards. There are some problems with the comparison of these hazards. They are, insufficient data for chemical toxicity standards for radiation doses and chemical toxicity not comparable residual risk from chemical toxicity regarded acceptable usually is orders of magnitude lower than from radiation The inhalation of soluble forms of uranium 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.The inhalation of insoluble forms of uranium in air produced no observable adverse effect. From this figure, a "minimal risk" inhalation level for humans of 8 µg/m3 is derived. 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 progeny 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 progeny 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. Current Standards of Inhalation: 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) 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) U.S. Occupational Safety and Health Administration (OSHA) regulations Permissible Exposure Limit - Time Weighted Average: soluble uranium: 0.05 mg/m3insoluble uranium: 0.25 mg/m3 (!)