Human Response Indicators

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

BrCa x (0.476) x (0.12) = 0.039 mg/day Br

x Ca = 0.68 mg/day

Standard man breathes 9.6 m3 of air in an 8-hour day, so the resulting concentration limit is 0.68/9.6 =

0.07 mg/m3. This is 40% higher than the OSHA standard for soluble uranium of 0.050 mg/m3.

Consequently, the OSHA limit is somewhat conservative for exposures to soluble/transportable (i.e., Class

D) uranium.

2.4.1 Human Response Indicators

Most data on human response to uranium exposure comes from accidental exposures (generally

UF6 releases). Accidental exposures to UF6 have resulted in fatalities on at least three occasions. The

primary cause of injuries and fatalities has been HF that was formed by hydrolysis of UF6, rather than

exposure to UF6 itself. Several individuals who received high, non-fatal exposures experienced

pulmonary edema, nausea, vomiting, abdominal cramps, and chemical burns on the skin due to HF

exposure. In addition, urinary abnormalities, such as transient albuminuria (albumin in urine) and the

presence of red cells and casts, were observed, as was retention of nitrogenous products such as urea and

non-protein nitrogen in the blood.

The urinary and blood abnormalities are indicators of kidney damage, and are the result of

inhibited resorption in the tubules. Animal studies indicate that urinary abnormalities can be observed

after exposures that are well below lethal levels. In addition, urinary abnormalities such as proteinuria

(protein in urine), glucosuria (glucose in urine), and polyuria (increased urine volume) have all been

observed following uranium exposure, as has the presence of certain enzymes in urine. Of all these

abnormalities, glucosuria appears to be the most sensitive and most nearly proportional to uranium

exposure.

Once absorbed into the blood, uranium is distributed to bone and kidneys, with a portion of the

uptake being generally distributed throughout the body. For inhaled uranium, residence time in the lungs

depends upon the solubility of the material. Material that is deposited in the lungs is cleared via the

bloodstream, the pulmonary lymph, and the gastrointestinal (GI) tract. Approximately 1 % of the uranium

is absorbed into the bloodstream from the GI tract.

In the event of an acute exposure to highly transportable (Class D) uranium compounds, urine

samples should be collected 3-4 hours post-exposure and analyzed for uranium as soon as possible. If the

uranium concentration is less than 2.0 mg/L, it is unlikely that any significant kidney damage has occurred

or will occur. However, it is important to check the urine for biological indicators of damage at any

exposure above 2.0 mg/L. While the most sensitive indicators are increased volume and glucose levels,

these are useful only if data on what is "normal" for the individual involved are available. Lacking that

information, it is best to check for albuminuria as an indicator of kidney damage. If kidney damage is

suspected, a specialist in urinary disorders should be consulted. In general, a urine uranium level greater

than 6.0 mg/L will produce some level of albuminuria. A level of 20 mg/L indicates a very serious

exposure with potentially life-threatening consequences and would indicate the need for immediate

hospitalization.

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