THE QUANTITATIVE MOVEMENT OF MANGANESE-54 IN A MODEL FOOD CHAIN

PAUL KENNETH KEARNS, Purdue University

Abstract

Manganese-54 (('54)Mn) is an activation product released in the radioactive effluents of commercial nuclear reactors. Concern exists over the potential risk to man from the consumption of ('54)Mn contaminated fish and seafood. The quantitative movement of ('54)Mn through an aquatic food chain into a mammal was investigated to help evaluate the hazard to man. Steady state ('54)Mn concentration factors for Chlorella spp., Daphnia magna, and yellow perch (Perca flavescens), where water was the only source of the radionuclide, were 2578, 17014, and 10.9, respectively. Biological half-lives for ('54)Mn in Chlorella, Daphnia, and yellow perch were determined to be 0.32, 1.2, and 8.3 days, respectively. The transfer of ('54)Mn from an aquatic food chain to normal and iron-deficient mice was investigated. Twenty-four hours after ingestion of ('54)Mn contaminated fish, iron-deficient mice were found to have more ('54)Mn in the liver, kidney, and carcass than normal animals. The biological half-life for ingested ('54)Mn in mice was 10.2 days. Associated dose calculations revealed that the present International Commission on Radiation Protection (I.C.R.P.) values for the fraction of ('54)Mn retained following ingestion (f(,w)) resulted in an overestimation of dose for normal individuals. However, calculations based upon the results of this research show that doses to iron-deficient animals were 71% and 77% larger for the whole body and liver than those determined using I.C.R.P. figures. This suggests that iron-deficient individuals such as the malnourished individuals, menstruating women, and pregnant women may not be adequately protected against inadvertent consumption of ('54)Mn due to the increased Mn absorption capacity they possess. Studies with intraperitoneally injected carrier-free ('54)Mn revealed minimal differences in ('54)Mn distribution and retention between normal and iron-deficient mice. No differences in retention or distribution of ('54)Mn were detected 7 days after injection. The biological half-life of intraperitoneally injected ('54)Mn was determined to be 9.9 days. This research showed that the transfer of ('54)Mn from an aquatic food chain to a mammal was increased in iron-deficient mice and that dose estimates using I.C.R.P. values for f(,w) underestimated the dose to iron-deficient individuals. Other activation products may also have increased absorption in nutritionally deficient individuals, and investigations into the possible increased dose from the inadvertent consumption of such activation products are warranted. Values of f(,w) in I.C.R.P. Publication #2 provide conservative protection for the general public; however, they may need to be refined for critical portions of the population such as the iron-deficient.

Degree

Ph.D.

Subject Area

Public health

COinS