The gastrointestinal absorption of plutonium and americium in the hamster

Abstract

Plutonium-239 and americium-241 were administered to adult hamsters in various chemical forms and their absorption from the gut was measured. The results have been compared with published data on other species in order to derive values for the estimated absorption of these actinides in man. On the basis of current knowledge, the best values for adults would appear to be: 0.05% for americium, 0.01% for plutonium ingested in soluble form, and 0.0001% for plutonium ingested as the dioxide. Plutonium dioxide should be considered as soluble if a significant proportion (greater than 5%) of the activity is in particles less than 25 nm in diameter.

ICRP Publication 141: Occupational Intakes of Radionuclides: Part 4

“…Analysis here (assuming s s = 10 −4 d −1 ) for a freshly prepared americium oxide gave f r = 0.6 and s r = 1 d −1 (giving assignment to Type M) for particles of size <0.025 µm, f r = 0.9, and s r = 4 d −1 (giving assignment to Type F) for particle size range 0.025–1.2 µm. For an AmO 2 suspension aged for 4 months in water, analysis here gave f r = 0.9 and s r = 3 d −1 for particles of size <0.025 µm, and f r = 0.7 and s r = 3 d −1 for particles in the size range 0.025–1.2 µm, giving assignment to Type M. (901) Stather et al. (1979a,b,c) studied clearance from the lungs of hamsters after inhalation of actinide oxides, either alone or in combination with other metals.…”

“…(1979b, 1984). For both species, the amounts of 239 Pu deposited in tissues from blood were <0.1% ILD at 30 d and <0.4% ILD at the end of the study (360 or 540 d; Stather et al., 1979a). Analysis here gave f r <10 −4 and s s = 5 × 10 −6 d −1 , with assignment to Type S. (765) Lataillade et al.…”

“…Investigations indicated that this was related to the fraction of particles that penetrated a 100-nm filter, then referred to as the ‘ultrafilterable’ fraction, and probably to particles within it of ∼1-nm diameter (e.g. Stather et al., 1979a; Stradling et al., 1980). Particles with physical diameters <100 nm are now described as ‘ultrafine particles’ or ‘nanoparticles’.…”

“…In the presence of sodium, ETD was far higher, between 6% and 38% ILD at sodium:plutonium ratios between 7:1 and 270:1, but there was no correlation with the ratio. Stather et al. (1979a) reported the result for a sodium:plutonium ratio of 27:1, for which ETD was 34% ILD.…”

Physicochemical factors that affect metal and metal oxide nanoparticle passage across epithelial barriers

“…In vivo studies have shown intestinal absorption of particles to be size‐dependent, with smaller particles (polystyrene microspheres, colloidal gold) being absorbed to a greater degree than larger ones 134, 135. Studies with highly insoluble radioactive metal NPs have shown extremely low transfer into blood following GI tract exposures,125, 136 but with some evidence that a negative surface charge promotes the absorption of the smallest particles 137. Electron microscopy with elemental analysis has identified nanosized particulates in liver, kidney, and colon tissue samples from humans 138–140.…”