Absorption and Retention of Cobalt in Man by Whole-body Counting

Abstract

Retention of 60Co given intravenously or orally as 60CoC2 to human subjects was measured by whole-body counting for periods of up to 1018 days. Intravenous 60Co was retained for long periods, as much as 9–16% of the dose being eliminated only with a biological half life of about 2 yr. The absorption of orally administered 60CoC2 depended on several factors, especially on the amount of stable cobalt given. Only 5% or less of a trace dose (containing less than 1 μg Co) was absorbed but this increased to more than 20 % when larger quantities of stable cobalt (1.2 mg) were given. The absorbed fraction of an oral dose was apparently retained by the whole body in a similar way to 60Co given intravenously. Results of serial counts over the liver using a collimated NaI detector, indicated that 60Co was concentrated in this organ in excess of the average whole-body concentration even in subjects measured after 1000 days. Our estimates suggested that the amount of 60Co present in the liver was, on average, about one fifth of the total body content.