Agricultural Products and Wildlife Sampling
Another potential pathway for contaminants to reach humans is through the food chain. The ESER Program samples multiple agricultural products and game animals from around the INEEL and Southeast Idaho. Specifically, milk, wheat, potatoes, garden lettuce, sheep, big game, waterfowl, doves, and marmots are sampled. Milk is sampled throughout the year. Sheep are sampled during the second quarter. Lettuce and wheat are sampled during the third quarter, while potatoes and waterfowl are collected during the fourth quarter. See Table A-1, Appendix A, for more details on agricultural product and wildlife sampling. This section discusses results from milk, lettuce, wheat, and large game sampled during the third quarter of 2002. A summary of approximate minimum detectable concentrations (MDCs) for radiological analyses is provided in Appendix B. There are no regulatory standards for radionuclide concentrations in agricultural products or wildlife tissues.
Milk samples were collected weekly in Idaho Falls and monthly at nine
other locations around the INEEL (Figure 12) during the fourth quarter of
2002. All samples were analyzed for gamma emitting radionuclides.
Samples are analyzed for 90Sr during the second and fourth
Data for 131I and 137Cs in milk samples are listed in Table C-8. Iodine-131 or 137Cs were not measured above the 2s value in any milk sample during this quarter. Iodine-131 was detected in one sample, the October sample from Roberts, exceeding the 2s value. No samples had 137Cs concentrations greater than their 2s uncertainty.
Strontium-90 was measured in four samples above the 2s value. The
detection of 90Sr in milk around the INEEL at very low
concentrations is not unusual and is indistinguishable from 90Sr
levels expected from historical fallout events (e.g. from nuclear
weapons tests and Chernobyl) (EPA 1997). There are no established limits
for 90Sr in milk but, for comparison, the EPA has set the
limit for 90Sr under the Safe Drinking Water Act at 8 pCi/L
(0.3 Bq/L). This limit is based on a 4 mrem per year exposure limit and
the assumption that two liters per day are consumed. The maximum
concentration (0.84 ± 0.72 pCi/L [0.03 ± 0.02 Bq/L) measured in milk
during the fourth quarter, 2002 is many times lower than the 8-pCi/L
limit. All resulst are reported in Table
C-9, Appendix C.
Nine potato samples were collected from area growers and from out-of-state locations. All samples were analyzed for gamma emitting radionuclides and 90Sr. No 90Sr was detected in any of the samples. Cesium-137 was measured in one sample from Mud Lake above its respective 2s value. The concentration of 137Cs from Mud Lake was 3.4 ± 3.3 pCi/kg (dry) (0.13 ± 0.12 Bq/kg [dry]).
Large Game Animal Sampling
Three game animals were sampled during the fourth quarter of 2002. All
were killed as a result of vehicular collisions. These accidents
involved two mule deer (Odocoileus hemionus)
and one elk (Cervus elaphus). Efforts were made to collect
samples of thyroid, liver, and muscle tissue from each animal, but due
to their condition at the time of sampling not all animals provided all
samples. Cesium-137 and 131I data for all big game samples
are listed in Appendix C,
Each sample collected was analyzed for gamma emitting radionuclides. Liver and muscle tissue of all animals had detectable concentrations of naturally occurring potassium-40. Cesium-137 was measured in the liver tissue of the elk sampled on October 14, 2002 above the respective 2s value. No 131I was measured in any game sample for the quarter.
The concentrations measured in the above samples are
within the range of values for samples collected in the past. Likewise,
the presence of 137Cs is commonly associated with plant
uptake of fallout from past weapons testing and nuclear accidents (i.e.,
Eleven waterfowl were collected during 2002: two each from the control locations of Mud Lake and Heise, three from the northeast Test Reactor Area (TRA) pond, and four from the TAN pond. All were analyzed for gamma emitting radionuclides with a subset analyzed for 90Sr, 238Pu, 239/240Pu, and 241Am. Concentrations of radionuclides measured in edible tissues are shown in Table 4. Seven waterfowl had measurable levels of at least one radionuclide in edible tissue. Of the radionuclides measured at each location, Mud Lake, the TRA NE pond, and TAN, each had three. Curium-141 (141Cm), niobium-95 (95Nb), and 90Sr were detected at concentrations greater than their 2s values in the muscle tissue of three of the waterfowl sampled. No 137Cs was measured above the 2s concentration in any edible tissue. Duck hunting is not allowed on the INEEL, but a maximum potential exposure scenario to humans would be someone collecting a contaminated duck and immediately consuming all muscle, liver, heart, and gizzard tissue (average 225 g). The maximum potential dose from eating 225 g (8 oz) of meat from the most contaminated ducks collected in 2002 was estimated to be 0.004 mrem. This dose is an order of magnitude lower than last years estimated dose of 0.89 mrem. This is attributed primarily to the fact that waterfowl from the TRA Warm Waste Pond, containing low levels of radionuclides, were not taken in 2002. This dose is far less than 240 mrem we receive each year from ambient sources and the 100 mrem per year DOE regulatory dose limit. Results for all duck samples are listed in Table C-13 of Appendix C.
Table 4. Measured radionuclides in edible tissues of waterfowl.