Dose due to 40K

The dose due to 40K has been estimated. Potassium is one of the most abundant elements in nature, being approximately 2% of the Earth's crust. Potassium has three isotopes 39K, 40K and 41K, two are stable while 40K is radioactive with a half life of 1.2x109 years; there is 0.0117% 40K-to-K ratio. Potassium plays an important role in plants, animals and humans growth and reproduction. Due to the fact that K is an essential element for humans, 40K is the most abundant radioisotope in human body. In order to keep good health conditions K must be intake at daily basis trough food and beverages, however when K in ingested above the requirements produce adverse health effects in persons with renal, cardiac and hypertension problems or suffering diabetes. In 89.3% 40K decays to 40C through β-decay, in 10.3% decays through electronic capture and emitting 1.46 MeV γ-ray. K is abundant in soil, construction materials, sand thus γ-rays produced during 40K decay contribute to external dose. For K in the body practically all 40K decaying energy is absorbed by the body; thus 40K contributes to total dose in humans and it is important to evaluate its contribution. In this work a set of 40K sources were prepared using different amounts of KCl salt, a γ-ray spectrometer with a NaI(Tl) was characterized to standardized the sources in order to evaluate the dose due to 40K. Using thermoluminescent dosemeters the dose due to 40K was measured and related to the amount of 40K γ-ray activity. (Author)