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Sunday, June 23, 2019

Basis for protection standard for uranium


Basis for protection standard for uranium
Uranium, a terrestrial radionuclide, is naturally present in the environment – in soil, rocks, in sea water, ground water, in food in the human body itself. The mass concentration of uranium varies from place to place depending on the environmental conditions. Natural uranium consists of three isotopes of uranium-238U, 235U and 234U with different half-lives. The longest-lived 238U has a half-life of 4.5 billion years. Typically, the soil concentration is about 3 parts per million (ppm).
In addition to its radioactive nature, it is, as water soluble uranium compounds, is chemically toxic. Uranium gets deposited in the kidneys due to its physicochemical properties. The US EPA (2001) and WHO (2011) standard for uranium in drinking water is 30 micrograms per liter which is equivalent to 0.75 Bq/liter. The threshold limit value (TLV) (ACGIH, 1994) in air in work environment for insoluble uranium is 0.2 mg/m3.
The protection standards for uranium (soluble) is limited by the chemical toxicity, while for insoluble compounds, the protection standards are based on radiological considerations.