Answer to Question #450 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I am an engineer and have ingested uranium. The levels in my hair are about 32 ug/g, found in several different hair analysis tests over a period of several months. My questions are, what is considered a dangerous level of uranium, what organs store the uranium, and what are the health implications? I understand that this information will not substitute for seeking advice from a medical professional. Please post the answer since I am currently unable to access my email. Thank you. Scott
Uranium, as you know, is a heavy naturally occurring metal that is found just about everywhere in nature. Although radioactive, it has a very low specific activity (i.e., the amount of radioactivity per gram) and thus, being a heavy metal, is considerably more hazardous from the standpoint of chemical toxicity. Indeed, for natural uranium the chemical toxicity is the overriding consideration and is approximately the same as the chemical toxicity of lead.
Animal studies have shown that sufficiently high doses of uranium ingested into the body will produce damage to the kidneys, and at still greater doses may cause death. However, there are few human data available and those that are available seem to suggest that ingested uranium may not be very toxic to humans. There are no known deaths from oral intake of uranium and studies with animals suggest that an acutely toxic dose in humans would be very large and that intakes on the order of several to several tens of grams would be required for even slight effects.
Before the discovery of insulin, uranium was used therapeutically for the treatment of diabetes with daily doses in the milligram or even greater range; no poisonings were reported. This is also consistent with studies of persons who have suffered massive intakes of uranium (typically through inhalation from industrial accidents). However, largely based on animal studies, limits have been established by the U.S. Environmental Protection Agency and other governmental bodies for uranium in water and air. As a heavy metal, uranium expectedly is excreted in the hair.
Assuming that the analytical results are correct (and this is subject to question and will be discussed below) the level that is cited—32 ug/g—is certainly on the high side although it could fall at the high end of the normal range, depending on where the person lives and dietary factors. Hair analysis, however, is subject to numerous errors and the effects of contaminants, not a trivial problem in the case of uranium which is naturally present in water and soil.
Hair analysis is not the standard nor an accepted way of evaluating exposure to or intake of uranium. A more appropriate test would be urinalysis, which could also include an examination for various indicators of kidney damage such as protein, casts, glucose, and nonprotein nitrogen or other biomarkers associated with kidney damage or reduced kidney function. You indicate that you have ingested uranium but do not specify the source, amounts, or type or chemical species, or time frame, all of which are important in determining the actual uptake of uranium and the potential for adverse effects.
It is well known that absorption of uranium from the gut is small, and typically only a few percent of the uranium ingested is absorbed via the gut. Once absorbed into the body, most of the uranium is quickly excreted via the urine. A small fraction is retained in the skeleton, which is the primary depot for uranium in the body. If you have additional questions please contact our website editor, Gen Roessler. She will give you information so that you can contact me directly.
Ron Kathren Professor Emeritus
Answer posted on 27 November 2000. The information and material posted on this website is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Website. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.
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