no significant losses from the skeleton wWere reported during a 250 q bored nichchee eased absorp tion of actinides has been reported when adeings ating agents or citrate comple xes. . The percen tage wren tay Administered Pu absorb ed in the GI tract of rats ineres eed 700 fen when a . nistered with DTPA Plus citrate (1.7% of administered dose) when coeeare ans absorption of Pu nitrate (0.0011%) (Baxter and Sullivan, 1972) rt increaving anon admini stered separately, were slight ly less ef fective rption, 0. and 0,79% of absorbed dose res ti (gee retention was highes t with citrate (0.091%), "pallo u ef a)” o ) also reported that neptun ium citrate was more readily absorbed than N nagnitede that Np absorption in the gut was higher than Pu by an order of . + Scott et al. (1949), using 24lanci 3 and 242 (mCl3, estimat and 0.05%, respectively, were absorbed in the GI tract. Comparablevalues were Teported using BkCl3 and *53BkC14 (Hungate et al., 1972), Elevated GI Buldakovet af.(1970) ne animal s has been emphasized by severa l investigators . reported high absorption and skel tal young dogs. Ballou (1958) and Baxter and Sul li ) eatimated chac absorption in young rats was from 2 to 100 ti times aeBre greate atee r then th ree f gtat Pu Moskalev et al. . (1969) re ported on the effects of continuousi aly y feeding 23 2 39 parate ro rats from age 3 months till death. The skeleton burden was always mes the liver burden with the result that 5 of 68 rats develo osteosarcomas with an estimated ed average bone dose of 57 rads P et crac eenee Eeeeundant literature that absorption of actinides from the € bloodstream is almost insignific ant und er most conditi . Potential hazards may exist, howev er, if actinides are present with complexing oxPoee or chelat d. ing agents g , . if a bsorption is continuous, or if young animals are Avatlable literature indicates that the epidermis of smal] mamma ls is an . ective parrter fo the absorp tion of transuranics, particular ly the insoluble nompound most ; ely to be found in the environment. Increased absorption (Oakley andThompson,1955;BuldakorofarnsopubLity of plutonium compou nds high levels of absorption and retention have been repo tedwi ch dewey (992) and intramuscular admin istrations (ICRP, 1992; Durbin” 9) fee a nas Co puncture wounds ceee eussand intramuscular injection, which may Sustained under natural condit i cane ekereeeePresent Plutonium uptake routes most likely co resul t ie etenticent . on burdens. Langham et al,, 1962, reported no systematic absorp tion Plutonium oxide when it was applie d to abraded skin of rabbits Wh solution of PuCl3 in dimethyl sulfox ide was placed on the naked sole of a. oe foots 0.26% of the appli ed dose was detected in the circu lating blood wath n3 rr] ures (Watters and Johnson, 1970), Khodyreva (1968) applied Plutorate (pHs) to the skin of rabbit s and estimated 0.15% was absor bed and retained after 14 days. Hungate et al. (1972) found that 0.03% per om? of “ einsteinium was absorbed when 0.01 N nitric acid was applied to naked rat skin, A maximum of 1.2% of Pluto nium metal implanted subcutaneously 1 bbi and mice was absorbed and distribute d throughout the body durin lifett : (Lisko and Kisileleski, 1953). In their studies, the liver/skeleton u tak ratios were dissimilar between the two species, probably reflecting the rapid 388 liver clearance rate reported in numerous studies of the rat. The average rat skeleton contained almost 10 times more plutonium than the average rabbit skeleton. Osteogenic sarcoma of the spine was reported from the rat with the highest burden. The results of their data indicate the desirability of obtaining more information on plutonium, and other transuranics, uptake in numerous species of animals. Weeks and Oakley (1953, 1954) reported plutonium absorption as high as 2% with 10 N nitric acid and 0.3% with 0.1 N nitric acid after 5 days. Oakley and Thompson (1955) reported increases in absorption with an increase in depth of administration. Using Pu (NO3), with 0.1 N nitric acid, an increase in percentage of administered dose absorbed from 0.33% in intact skin to 2.7% from subcutaneous injection with a corresponding increase in liver deposition was reported. Cable et al. (1962) estimated up to 12% retention in the lymph nodes and 4.8% in bones after 7 days when Pu (NO4), was injected intradermally. Their data indicated that percent absorption may be inversely related to dosage as Thompson (1967) later suggested. Scott et al. (1948) and Taylor (1969) have reported absorption values of 65 and 51% of Pu0yClo and plutonium nitrate, respectively; 256 days after administration of Pud.Cly 47% was retained in the skeleton. Whereas rather low levels of uptake of transuranics by means of ingestion or parenteral absorption into vertebrate systems may be important particularly in chronic situations, laboratory experiments indicate that inhalation is the most hazardous natural route of entry. Inhaled insoluble Pu produced Lung tumors (Moskalev, 1972; Bair and Thompson, 1974). Significant increases in lung tumors of rats were reported with accumulated dceses of 50 rads using inhaled 77%pu citrate (Moskalev, 1972) and 9-32 rads with soluble *38py (Sanders, 1973). Several works provide summaries of inhalation studies relating to the retention, translocation, and biological effects of Pu and in some cases other transuranics (Abrams ¢t al., 1947; Bair and Willard, 1963; Morrow, 1966; Buldakov, 1970; Sanders, 1973; ICRP, 1972; Bair et al., 1973 and others). The results of these studies indicate that absorption from the lung varies from Absorption, fate, and effects of inhaled less than 1% to as much as 10 to 15%. transuranics depend on such factors as solubility, chemical form, respiratory rate, and particle size. In addition, Bair et al. (1966) and Buldakov et al. (1970) have pointed out important differences between acute versus chronic Insoluble Pu compounds are retained exposures. (239pu 0.) in the lung and associated lymph nodes and are translocated to the bone and liver very slowly, where they are retained; hence, resulting pathologies are somewhat confined to these tissues, Soluble Pu compounds are translocated relatively rapidly via the blood to bone and liver and, to a lesser extent, lymph nodes, kidney, spleen, and gonads. Translocation rates and retention times differ between some species as rats loose Pu from liver much more rapidly than dogs. Stannard and Morrow (1956) demonstrated the importance of respiratory rate and volume to Pu deposition. Bair and Willard (1963) {ndicated that deposition and retention of Pu was greatest when inhaled as large particles of 0.6 uw CMD. Inhaled Pu Q2 and more soluble Pu compounds result in lymphopenta. Bafr et al. (1966) reported all but two dogs with less than 0.003-0.0002 wCi/g Pu O59 in lung showed persistent lymphopenia and leukopenia throughout their life span. Bair et al. (1973) reported there is a possible relationship between Pu-induced lymphopenia, lymp node pathology, decreased immunological capability (Dilley, 1970), and the pathogenesis of Pu-induced pulmonary neoplasia. 389