Natural radionuclides in human hair

Abstract

Naturally occurring radionuclides of terrestrial origin, such as 238U, 235U, 226Ra, 210Po and 210Pb, are present to various degrees in all environmental media, including the human body. Like other pollutants, many natural radioactive substances also accumulate in hair. In this article, the transfer to human scalp hair and typical concentrations in hair are presented for some natural radionuclides. Uranium is a primordial radioactive element ubiquitously present in the Earth’s crust. Natural uranium consists of a mixture of three radioactive isotopes: 238U (99.2745% by mass), 235U (0.7200%) and 234U (0.0054%). All three isotopes are α-emitters with very long half-lives. In addition to uranium isotopes, 226Ra, 210Po and 210Pb are taken into account. They occur widely in the natural environment as they are part of the 238U decay chains. All these radionuclides are transferred from the environment to the human body via inhalation and the ingestion of foodstuffs and water. The intake of natural radionuclides varies depending on the diet and residential location. Consequently, the concentrations in human hair vary greatly. The concentrations of uranium, 210Pb and 210Po in human hair have been observed to vary between <0.5-140,000 ng/g, 0.7-10 mBq/g and 0.4-59.3 mBq/g, respectively. Natural variation in the transfer of natural radionuclides into hair complicates the use of hair as an accurate bioindicator.