Radionuclide levels in caribou of northern Alaska in 1995-96

Updated 2000-04-18

Caribou (Rangifer tarandus) were sampled (1995-96) from a mortality event near the Project Chariot site (NW Alaska), the location of a radiotracer experiment in the 1960’s, and reference sites. Radionuclide levels in muscle and bone and the cause(s) of the mortality were determined due to concerns of local residents. Bone gross alpha mean activity (n = 65) was 130.0 Bq/kg, and varied significantly (< 0.01) from 73.3 to 168.0 Bq/kg among locations. Bone and muscle gross beta mean activity was 510.4 and 9.78 Bq/kg. Bone strontium-90 mean activity (n = 58) was 137.8 Bq/kg. Muscle potassium-40 mean activity (n = 65) was 183.0 Bq/kg, and significantly varied from 76.0 to 104.4 Bq/kg by location. Muscle cesium-137 mean activity (n = 65) was 6.67 Bq/kg, ranged significantly from 0.74 to 15.6 Bq/kg by location, and increased with increasing body condition score. Bone potassium-40 mean activity ranged from 18.9 to 47.4 Bq/kg, and muscle strontium-90 ranged from 8.89 to 20.0 Bq/kg. Radionuclide concentrations were at expected levels and low in some cases as compared to Canadian caribou studies.

This is not a National Implementation Plan (NIP) project

Time frame

Project time span
1995 - 1999
Data collection
1995 - 1996
Data processing
1997 - 1998
Data reporting
1998 - 1999

Contact information

Contact person
Todd M. O'Hara
Dept. of Wildlife Management North Slope Borough Box 69 Barrow, Alaska 99723 USA
1 907 852 0350
1 907 852 0351

Parameters and Media

Parameter groups measured/observed/modelled
Heavy metals
Other metals/elements
Media sampled/studied/modelled
Terrestrial mammals
Additional information or further specification of types of data / information collected, species / tissues / organs sampled, etc.

Species sampled: caribou (Rangifer tarandus) Sampling sites: Point Hope, Cape Thompson, Teshekpuk Lake, Barrow, Red Dog Mine matrices sampled: muscle and bone other information collected: age, body condition score Radionuclides analyzed: Cs-137, K-40, Sr-90


Regions studied
Stations or areas where observations are made

see above

Data availability

Are data archived or planned to be archived at an AMAP Thematic Data Centre?
References to key publications (or planned publications) and data reports
O'Hara et al., 1999. Radionuclide levels in caribou of northern Alaska in 1995-96. Arctic 52(3):279-288.
Samples/specimens archived in specimen banks?

Methods & Procedures

Procedures and methodology used for, e.g., sampling and sample storage, sample pretreatment, extraction and analysis, including which laboratories are involved, references to methods employed, etc.

Caribou were sampled from many areas on or near the North Slope of Alaska. Animals found dead or euthanatized (Cape Thompson and Point Hope) and hunter-killed (Barrow, Point Hope, Teshekpuk Lake, and Red Dog Mine) were examined and sampled for this study. The number of caribou examined and/or sampled are listed below; six in Point Hope in March, 1995; six from Barrow in March-April, 1995; 101 from Cape Thompson in 1995 (65 of these sampled and 30 analyzed); nine from Teshekpuk Lake in July, 1995; 15 from Red Dog Mine in March, 1996. The total is 100 sampled, 137 examined, and 65 analyzed. Radioanalysis A contract laboratory (Lockheed Martin Lockheed Analytical Services, Las Vegas, NV) measured gross alpha and beta emissions (method LAL0060), Cs-137 and K-40 by gamma spectroscopy (method LAL0064), and Sr-90 (method LAL0196) in muscle and bone. Specimens (femur and associated muscle) were collected in the field and placed in sealed plastic bags, labeled, and frozen. All specimens were returned to the NSB-DWM freezer in Barrow, AK for logging and preparation for shipment to the processing laboratory (Diagnostic Services, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA). Upon arrival at the processing laboratory the muscle was trimmed from the bone. Muscle was homogenized using a food processor and placed in polypropylene containers provided by the contract laboratory. A band saw was used to prepare cross-sections of femur and placed in the container provided by the contractor. For all radiochemical analyses calibration and quality control (QC) included instrument calibration, initial and continuing calibration verification, quench monitoring standards, instrument background analysis, method blanks, yield tracer, laboratory control samples, and duplicate samples. All samples were analyzed as wet weight. Gamma spectrum analysis was all within QC criteria using High-Resolution Gamma Spectroscopy and activity reported as pCi/g. For gross alpha and beta, all criteria were met except for sample weight reductions were needed in some cases. Strontium-90 analyses were within criteria limits except for two samples that had yttrium recoveries slightly above the limits. Stable strontium carrier is added to the sample. Samples are dissolved using microwave digestion and the cations are concentrated using a strong cation exchange column from dilute acid. The cations are then eluted using 8 M nitric acid and evaporated to dryness. The residue is dissolved in Sr Spec column feed solution and passed through the Sr Spec column. The strontium is eluted with 0.05 M nitric acid and evaporated to dryness in a planchet. The strontium yield is determined by the weight of strontium nitrate on the planchet. The radiostrontium is counted several times over 2 weeks using a low background beta counting system (< 1.0 cpm beta). The ingrowth of Y-90 allows the activity of Sr-89 and 90 to be determined by regression analysis of the resulting counts. The counting efficiency is obtained using standard Sr-89, 90 and Y-90 activities. These data must be used to make corrections since the beta particle energies are different for Sr-89, Sr-90, and Y-90. Alpha and beta counting is conducted using a low background alpha/beta proportional counting system and counting efficiencies are determined from a plot of the counting efficiencies as a fraction of sample mass. The calibration standard used for gross beta is Sr-90 in equilibrium with Yttrium-90 and for gross alpha, Americium-241. The minimum detected activity (MDA, Bq/kg) range was 1.11-2.22 for Cs-137, 22.6-24.4 for K-40, 7.04-35.2 for Sr-90, 1.85-37.8 for gross alpha, and 2.96-75.9 for gross beta. Recovery was 118-119% for Sr-90, 92-99% for Cs-137, 100-105% for gross beta, and 107-114% for gross alpha. Levels at or near, and greater than the MDA were reported as measured. Detection limits were reported for each sample and nuclide. A few animals were reported as - (negative) activity (well below the MDA) and were recorded as 0 Bq/g. This occurred mostly for Cs-137 levels in muscle for those areas with low levels (Barrow, Cape Thompson, Point Hope). For all other locations, the Cs-137 activity was above the MDA and recorded as the measured level for all caribou tested. For gross alpha, the detected levels and averages are close to the MDA for muscle samples. Units were reported in pCi/g by the contract laboratory and summary statistics (means) will be reported as Bq/kg. The conversion was: pCi/g X 1 Bq/27 pCi X 1,000g/kg = Bq/kg. Age Estimates “Aging” of caribou was conducted by a contract laboratory (Matson's Laboratory, Milltown, MT) using the central (primary) incisor when available; when not available the first premolar was submitted. Teeth were extracted from collected mandibles and placed in paper envelopes. When pairs of matched teeth (both central incisors from one animal) were available these were submitted for comparison and quality control (a test of precision). For matched teeth if ages disagreed the age estimate with the highest score of reliability was used. A letter suffix (A = nearly certain age, B = some error possible, C = error likely) accompanied each age estimate that indicated reliability of the estimate based on the annulus pattern. Of 45 matched pairs of caribou teeth 28 (62%) agreed, 12 (27%) disagreed by 1 year, 4 (9%) by 2 years, and 1 (2%) by 4 years. Body condition (BC) score Body condition scores were determined as outlined by Kistner et al. (1980). Kistner et al. (1980) developed a field technique for evaluating physical condition of deer. This field technique is based on carcass fat at indicator depot sites (cardiac, omental, perirenal, and subcutaneous regions of the tail head and brisket) and muscle mass. Fat indices are rated by multiples of 5 from 0-15 and muscle is scored as 0 or 5. Body condition (BC) scores were set as emaciated (0-10), poor (11-40), fair (41-70), good (71-80) and excellent (81-95). Obtaining a complete BC score was not always possible because of time restrictions. Six fat depot sites are given scores of 0 (no visible fat), 5 (slight quantities of fat), 10 (moderate fat), and 15 (heavy fat), and muscle mass is ranked as 0 (if carcass is "bony") or 5 (full). A score can range from 0-95. Mean scores should be calculated for sex and age-classes separately if possible. Our sample sizes are small so this could not be done. Season of sampling is important as food is usually abundant in the summer and fall resulting in fat deposition, whereas fat is utilized during other times of the year. Bone marrow fat evaluation was used and is better suited for assessing very poor condition (Kistner et al., 1980; Ransom, 1965; Neiland, 1970). Subcutaneous fat is only present in good to excellent condition of most deer (Kistner et al., 1980). In emaciated animals serous atrophy occurs at these depot sites, especially the marrow cavity, and was examined in this study. Statistical Analyses Most statistics (means, standard deviations, ranges, linear regression analyses) were performed using Microsoft Excel for Windows version 7.0. The original data (pCi/g) was used for all calculation and analyses. SPSS for MS Windows (7.5.2) was used for the analysis of variance (ANOVA) and Tukey’s Highly Significant Differences (HSD) test.

QA/QC Information (what QA/QC procedures are implemented, laboratories involvment in QA/QC activities, model verification/validation routines, etc.)

see above

Additional Information

Is this a bi- AND multi-lateral project (i.e. a project involving cooperation between different countries)?
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