Toxicological/Biological Effects - doe-hdbk-1113-98_reaffirm_2005

DOE-HDBK-1113-98

Radiological Safety Training for Uranium Facilities

Module 101 Properties of Uranium

2. Toxicological/Biological Effects

The principal entry of uranium into the human system is due to either inhalation

or ingestion. Inhalation occurs either from release of volatile uranium

compound or from suspension of volatile uranium-laden aerosols. Ingestion can

occur when the uranium is introduced into water for consumption or the food

chain by plant uptake. When uranium is either ingested or inhaled, it is removed

from the body with a biological half-life varying between 6 and 5000 days,

depending on which organ has become contaminated.

Uranium tends to concentrate in the kidneys and the bones. Additionally, if

inhaled, the lungs are exposed. Internal exposure to uranium is controlled by

limiting the ingestion and inhalation of this element. These methods, along with

measurement techniques, are discussed in Module 104.

Most heavy metals, such as uranium, are toxic to humans depending on the

amount introduced into the body. For short-term (acute) exposures, the

toxicological effects are the primary concern, and acute exposures to significant

amounts of uranium may result in kidney damage. However, as the enrichment

of the uranium in the 235U isotope increases, so too do the effects of radiation

exposure in relation to toxicological effects.

Past industrial experience has proven that if there is a long-term exposure of

small amounts of uranium (chronic exposure), the radiological effects are the

primary biological concern. In fact, for chronic exposures, a development of

tolerance against the toxicological effects may occur. The principal radiological

hazard associated with uranium is due to the relatively high energy alpha

particles its radionuclides and daughters emit. A chronic exposure to these