The distribution of intracellular alkali metals in Reference Man

Abstract

A review of recent literature and a re-analysis of data used in Publication 23 of the International Commission on Radiological Protection (ICRP) have revealed several problems regarding the distribution of the predominantly intracellular alkali metals potassium, rubidium and caesium in ICRP Reference Man. In this paper we re-evaluate the distribution of the intracellular alkali metals in humans and we offer an approach for selecting reference concentrations for the organs of a typical adult human. For non-skeletal tissues, reference values for K, Rb and Cs are determined as a trimmed weighted mean of reported values remaining after studies involving apparently questionable populations or measurement techniques have been eliminated. The skeleton is treated as a special case, with explicit consideration being given to the heterogeneous distribution of these elements among different regions and different types of skeletal tissue. The most significant suggested changes for the intracellular alkali metals are for Rb in the skeleton and total body. ICRP Reference Man has a total Rb content of 0.68 g, compared with our estimate of only 0.25 g, and a skeletal Rb content of 0.21 g, compared with our estimate of only 0.013 g. This has important dosimetric implications for radiorubidium, because the retention model for Rb given in ICRP Publication 30 assigns a large portion of an intake to the skeleton on the basis of the large skeletal Rb content assigned to Reference Man in ICRP Publication 23.

A Biokinetic Model for Rb in Humans

“…Previously, the authors reexamined the organ masses and the steady-state distributions of K, Rb and Cs in a typical 70-kg adult male, age 35 y (Williams and Leggett 1987;Leggett and Williams 1986). Pertinent features of this reference male are summarized in Table 1.…”

“…Despite the large amount of physiological and medical information available on Rb, there does not exist a model that tracks the timedependent distribution of this element in the body over an extended period with much detail or accuracy. For example, the retention model for Rb given in Publication 30 of the International Commission on Radiological Protection (ICRP 1979) inaccurately portrays the skeleton as the tissue with the highest Rb concentration (Williams and Leggett 1987). Also, the ICRP model views all non-skeletal tissues as a single compartment and thus cannot accurately depict the heterogeneous distribution of Rb in soft tissues at early times (Ryan et al 1985 ) .…”

Lifetime accumulation of 137Cs and 40K in the ribs and sternum of an Austrian “mountain pasture” cow

“…Various investigations showed that K and Cs have many common properties but some tissues and organs discriminate quantitatively between those elements. Comprehensive studies concerning the distribution of alkali elements in humans were published by Williams and Leggett (1987) and Leggett et al (2003).…”

Clinical Effects of Cesium Intake

“…Cesium enters easily into the plant and animal systems and is deposited in soft tissues [12]. The total content of this intracellular form is very low, no more than 0.00131 g [13].…”