Milk Sampling

Milk samples were collected weekly in Idaho Falls and monthly at eight other locations around the INEEL during the fourth quarter of 2001.  All samples were analyzed for gamma emitting radionuclides.  Samples from four locations (Arco, Howe, Dietrich, and Roberts) were analyzed for ⁹⁰Sr. 

Iodine-131 was detected in two samples, from Roberts and Idaho Falls.  Three samples (Idaho Falls, and Rupert in November; and Blackfoot in December) had a ¹³⁷Cs concentration greater than their 2s uncertainty (Figure 12).  Of the four samples analyzed for ⁹⁰Sr all had concentrations greater than their associated 2s value.  Data for ¹³¹I and ¹³⁷Cs in milk samples are listed in Table C-8.  Data for ⁹⁰Sr in milk samples are listed in Table C-9, both in Appendix C.

Chemically, ⁹⁰Sr acts similar to calcium.  Therefore, it is expected that, if ⁹⁰Sr were present, it would be found in substances with high calcium content such as milk.  The EPA’s ERAM program samples milk from approximately 55 sites across the United States.  These data showed ⁹⁰Sr results in milk to be greater than the 2s level in about 63% of samples with a range of –0.15 to 2.12 pCi/L (-0.006 to 0.078 Bq/L) (EPA, 1997).  While ⁹⁰Sr levels in the three samples analyzed for ⁹⁰Sr were greater than their associated 2s values, all results were within the range measured across the United States.  All ⁹⁰Sr detected in fourth quarter ESER milk samples were at very low concentrations and indistinguishable from levels expected from ⁹⁰Sr released 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 in drinking water at 8 pCi/L.  This Safe Drinking Water limit is based on a 4 mrem per year limit and the assumption that two liters per day are consumed.  The maximum concentration [1.2 ± 0.7 pCi/L (0.05 ± 0.03 Bq/L)] measured in milk during the fourth quarter, 2001 is lower than the 8 pCi/L limit.  Data for ⁹⁰Sr in fourth quarter milk samples are listed in Table C-9 (Appendix C).