The U.S. Atomic Energy Commission Rocky Flats Area Office (USAEC-RFAO) funded this study Published in 1975. The cattle were sacrificed in November of 1973. Concentrations of Uranium (U), Plutonium (Pu) and Americium (Am) were measured in various tissues from ten (10) cattle collected from a herd which grazed on a pasture Northeast of the Rocky Flats Plant (RFP). The Pu concentrations were equivalent to those found in other herds grazing in areas where Pu in soil was above the U.S. average. The cohort Am was 1/4 to 1/2 of the Pu-239 concentrations in the same tissues.

Commercial cattle herds graze the natural vegetation immediately outside the fence around the RFP and drink water from streams draining from the RFP. Ten cattle were used as biological monitors to measure the uptake of Pu and other radionuclides in the tissue.

The history of this herd as related by the original owner is as follows: Since their purchase 5 or 6 years ago, each cow grazed from mid-May to the end of October in the RFP area of concern (5-6 months per year). One of the streams used by the cattle carried effluent from the RFP system, which included low-level radioactive process waste water until December 1973 when this waste water was diverted to holding ponds on-site. They received no supplemental feed and their drinking water came primarily from Walnut Creek. The rest of the year the cattle grazed on wheat alfalfa, or corn fields near Brighton, Colorado. Calves were born on the pasture land near the RFP during late May or early June of 1973. Study cattle from the Nevada herds grazed year round at their sites.

The history and vital statistics of the cohort cattle studied from the Roller Coaster, Searchlight. and Nevada Test Site (NTS) pastures near the NTS are as follows: The Roller Coaster herd had access to a range contaminated with Pu during the 1963 Roller Coaster series of above ground nuclear tests. The NTS herd grazed on ground zero areas where several atmospheric nuclear tests had been conducted in the early 1960's. both areas had radioactive contamination levels far greater than that considered to be "background". Despite contradictory results, the data suggests that the RFP cattle had higher exposure to Pu than the cattle from the Nevada areas.

Most of the uranium (U) concentrations found in the bovine tissues were in the range of those found in previous studies. A major exception was in the tracheo-bronchial (throat and lung area) lymph nodes. This suggests a higher uranium inhalation exposure for the RFP cattle than for other herds in the study. The average U-238 concentrations in soil sampled in an arc 5 miles from the RFP was 0.77 pCi/g dry soil. This was about three times the world wide average of 0.25 pCi/g.

There are natural uranium (U) deposits in the general area. The RFP has also processed and released large amounts of uranium. The Pu-239 data suggests inhalation exposures in the tracheo-bronchial lymph nodes (TBLN), were higher in the RFP adult samples than in the Nevada herds studied. Some of the Pu detected in the lung and tracheo-bronchial lymph nodes (TBLN) in the RFP herd may have come from resuspended dust inhaled during grazing. Vegetation was collected from various locations as remote as 15 miles from the RFP. There is no comparative data for concentrations of americium (Am). The other herds were not tested for this plutonium daughter radioisotope. Pu concentrations for water samples taken from Walnut Creek were 8 times greater than that for Am.

The authors stated that the results would have been higher for the RFP cattle if they had not been subjected to a 3-day delay from removal from pasture, to transfer to Nevada for sacrifice. This three-day delay in addition to the stress of transfer induced greater clearance of radionuclides due to diarrhea and dehydration. The clearance half time from the naso-pharyngeal (nose and upper throat) and tracheo-bronchial (lower throat and lungs) regions of the lung may be less than 24 hours for insoluble Pu; 40% of that is deposited in the pulmonary region, and has a clearance time of one day. The cattle groups from Nevada were sacrificed within 24 hours.

The range for Strontium-90 levels detected in the femur (bone) samples of the RFP cattle ranged from 2.0 - 5.8 pCi/g of ash with an average value of 3.4 pCi/g of ash. This is the mid-range found in cattle from Nevada during 1972. (The highest readings have been obscured by this "averaging"). Tritium levels detected in the blood of the RFP cattle ranged from 2,040 - 6,080 pCi/liter. The mid-range value was 3,320 pCi/L. These tritium levels resulted primarily from the ingestion of water from Walnut Creek which was contaminated with tritium during April and May of 1973. CDH tested samples during November of 1973 from Walnut Creek at Indiana Street that ranged from 2,400 pCi/L to 12,600 pCi/L with a mid-range value of 7,800 pCi/L. The use of mid-range values obscures the impact of the higher values.

"Contamination of Municipal Water Supplies in the Denver Metropolitan Area by the Rocky Flats Plutonium Plant" by Dr. Carl J. Johnson, MD, MPH presented at the Annual Meeting of the American Association for the Advancement of Science in San Francisco, CA in January 3-8, 1980. He reported that "...a major tritium release reached a peak of nearly 3 million pCi/L in May of 1973. Broomfield tap water reached a high of 18,780 pCi/L. Tritium levels in the urine of Broomfield residents measured as high as 8,100 pCi/L..." Dr. Johnson stated that Am would be of greater concern in time due to Am ingrowth from Pu, along with greater bioavailability.

Dose calculations from the consumption of liver from the Nevada cattle compared with the RFP cattle was 4 times greater for uranium and 6 times lower for Pu-239. Plutonium translocates to specific radiosensitive organs (uneven distribution). Uranium disperses and distributes uniformly within the tissues of the body. Therefore, the liver is a poor indicator for a comparison of uranium-to-plutonium bioaccumulation. The concentrations of uranium in the tracheo-bronchial lymph nodes (TBLN) in the five (5) young cattle was 2.3 times greater than that of the five (5) mature cattle. The gonads were tested on the RFP cattle only. Conversely, the uranium concentration in the gonads of the mature cattle was approximately 2.9 times higher than that of the younger cattle. The difference in gonadal concentrations may be due to the mature cattle having active hormone systems that may enhance uptake. The RFP cattle had high readings for Am in TBLN and gonads. Four of the five mature RFP cows were found to be barren. Gonadal tissue had higher concentrations of all actinides when compared to muscle. The results were high in addition to the TBLN. The plutonium concentration was greater in the RFP cattle than that for the Nevada herds in this study. The Nevada cattle were not tested for Am.