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Patricia A. Thomas¹ and Thomas E. Gates²

¹Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
²Saskatchewan Environment and Resource Management, Prince Albert, Saskatchewan, Canada

Abstract

The richest uranium ore bodies ever discovered (Cigar Lake and McArthur River) are presently under development in northeastern Saskatchewan. This subarctic region is also home to several operating uranium mines and aboriginal communities, partly dependent upon caribou for subsistence. Because of concerns over mining impacts and the efficient transfer of airborne radionuclides through the lichen-caribou-human food chain, radionuclides were analyzed in tissues from 18 barren-ground caribou (Rangifer tarandus groenlandicus) . Radionuclides included uranium (U) , radium (²²⁶Ra) , lead (²¹⁰Pb) , and polonium (²¹⁰Po) from the uranium decay series ; the fission product (¹³⁷Cs) from fallout ; and naturally occurring potassium (⁴⁰K) . Natural background radiation doses average 2-4 mSv/year from cosmic rays, external gamma rays, radon inhalation, and ingestion of food items. The ingestion of ²¹⁰Po and ¹³⁷Cs when caribou are consumed adds to these background doses. The dose increment was 0.85 mSv/year for adults who consumed 100 g of caribou meat per day and up to 1.7 mSv/year if one liver and 10 kidneys per year were also consumed. We discuss the cancer risk from these doses. Concentration ratios (CRs) , relating caribou tissues to lichens or rumen (stomach) contents, were calculated to estimate food chain transfer. The CRs for caribou muscle ranged from 1 to 16% for U, 6 to 25% for ²²⁶Ra, 1 to 2% for ²¹⁰Pb, 6 to 26% for ²¹⁰Po, 260 to 370% for ¹³⁷Cs, and 76 to 130% for ⁴⁰K, with ¹³⁷Cs biomagnifying by a factor of 3-4. These CRs are useful in predicting caribou meat concentrations from the lichens, measured in monitoring programs, for the future evaluation of uranium mining impacts on this critical food chain. Key words: caribou, cesium, food chain, lead, polonium, radiation dose, radionuclides, radium, risk, uranium. Environ Health Perspect 107:527-537 (1999) . [Online 27 May 1999]

http://ehpnet1.niehs.nih.gov/docs/1999/107p527-537thomas/ abstract.html

Address correspondence to P.A. Thomas, Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5B3. Telephone: (306) 244-4807. Fax: (306) 931-1664. E-mail: thomasp@sask.usask.ca

We appreciate the technical assistance of T. Bollinger, T. Swenson, K. Krieger, K. Sobey, and D. Dyck, and we thank the Saskatchewn Research Council for prompt sample analyses.

This research was funded by Saskatchewan Environment and Resource Management and Saskatchewan Health.

Received 13 October 1998 ; accepted 3 March 1999.