SWRHL-43r 1311 TRANSPORT THROUGH THE AIR-FORAGE-COW-MILK SYSTEM USING AN AEROSOL MIST (PROJECT RAINOUT) by Richard L. Douglas, Stuart C. Black and Delbert S. Barth Radiological Research Southwestern Radiological Health Laboratory ENVIRONMENTAL PROTECTION AGENCY Las Vegas, Nevada 89114 Published June 1971 This study performed under a Memorandum of Understanding (No. SF 54 373) for the U. S. ATOMIC ENERGY COMMISSION ------- This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately-owned rights. Available From The National Technical Information Service, U. S. Department of Commerce, Springfield, VA 22151 Price: Paper Copy $3.00; Michrofiche $.95 001 ------- SWRHL-43r 1311 TRANSPORT THROUGH THE AIR-FORAGE-COW-MILK SYSTEM USING AN AEROSOL MIST (PROJECT RAINOUT) by Richard L. Douglas, Stuart C. Black and Delbert S. Barth** Radiological Research Southwestern Radiological Health Laboratory* ENVIRONMENTAL PROTECTION AGENCY Las Vegas, Nevada 89114 Published June 1971 This study performed under a Memorandum of Understanding (No. SF 54 373) for the U. S. ATOMIC ENERGY COMMISSION *Formerly part of U. S. Department of Health, Education, and Welfare, Public Health Service, Environmental Health Service, Environmental Control Administration, Bureau of Radiological Health **Dr. Delbert S. Barth is presently Director, Bureau of Air Pollution Sciences, EPA, Triangle Park, N. C. 27709 ------- ABSTRACT Project Rainout was an experiment conducted to determine the transfer of 131I from forage to dairy cow milk when the radio- iodine was sprayed on the forage as an aqueous solution. Growing alfalfa, cut as green chop, and spread hay were used as forage. The peak activity in milk from cows consuming both types of forage occurred about one day after the start of feeding. The peak milk-to-peak forage ratio was 0. 013 for the cows fed hay and 0. 041 for the cows fed green chop. The hay fed cows secreted in milk an average of 4. 5% of the amount of 131I they ingested, while the green chop fed cows secreted 6. 1%. ------- TABLE OF CONTENTS Page ABSTRACT i LIST OF TABLES iii LIST OF FIGURES iv INTRODUCTION 1 PROCEDURES 3 A. Experimental Design 3 B. Preparation, Deposition and Assessment of Hydrosol 7 C. Meteorological Instrumentation 10 D. Forage Collection and Animal Husbandry 11 E. Sampling Techniques I/ F. Sample Analysis 13 RESULTS AND DISCUSSION 15 A. Deposition and Assessment of Radioiodine Solution 15 B. Effective Half-life on Growing Alfalfa 23 C. 131j Activity in Dairy Cow Forage 23 D. 131I Activity in Milk 28 CONCLUSIONS 37 REFERENCES 38 DISTRIBUTION ------- LIST OF TABLES Table Page 1. Groups of cows and feeding schedule 6 2. System efficiency and minimum sensitivity for 131j 14 3. 131j deposition on planchets 16 4. Amount of precipitation at each sample position 18 5. Meteorological data during and after deposition September 29, 1966 19 6. Air sampler data during and after deposition 21 7. Summary of the daily averages of 131j concentrations (|j.Ci/kg) on forage 25 8. Mean concentrations of *31j in miik by groups (pCi/liter) 29 9. Effective half -lives of 131I in milk 33 10. Comparison of results from four studies 34 11. Percent of ^ I ingested which was secreted in milk 36 111 ------- LIST OF FIGURES Figure 1. Layout of EPA Experimental Farm 4 2. Project Rainout study area 5 3. Aerosol spray procedure 8 4. Histogram of droplet size distribution 22 5. Mean concentrations of I in growing alfalfa 24 6. Mean values of ^ I in green chop 26 7. Mean values of ^ I in hay 2? 8. Mean concentrations of I in milk of Group I cows 31 i -31 9. Mean concentrations of -'I in milk of Group II cows 32 IV ------- INTRODUCTION The major mission of Radiological Research, a program of the Southwestern Radiological Health Laboratory, Environmental Pro- tection Agency, is to study the transfer of radioiodine from the atmosphere to man via the route air-forage-cow-milk-man. Our program is strongly field-oriented, and includes an experimental farm at the Atomic Energy Commission's Nevada Test Site. This farm consists of 17 acres of irrigated land, a 24-cow dairy herd, and associated support facilities and equipment. Whenever possible, we conduct our studies using contamination released from Plowshare cratering experiments, reactor runs, and inadvertent releases from underground weapons tests at the NTS. Since these sources of radioactivity are relatively limited, we supplement them by semicontrolled releases of radio- active material at our farm. Two such studies (Projects Hayseed and Alfalfa) have been conducted prior to the present (7 8} study. ' They both involved the release of a 3 I-tagged diatomaceous earth aerosol over growing forage, which was sub- sequently cut and fed to dairy cows. Although these studies differed in aerosol particle size and the type of forage used, they were both designed to study the deposition and uptake of a dry particulate aerosol. While deposition of radioiodine as a dry aerosol may be a major fallout mechanism, other methods are certainly possible. One of these is the removal of gaseous iodine from a cloud by the scrub- bing action of rain, known as "rainout" or "washout". In such ------- cases the iodine is presumably deposited on forage as an aqueous solution. For this type of deposition, very little information is available as to either the scrubbing mechanism or the behavior of the activity after deposition on forage. In addition, the decon- taminating effects of clean water added after deposition of the activity, commonly referred to as washoff, are little understood. This additional precipitation might result from continuing rainfall after the cloud has passed, or from applying irrigation water after the contaminating event. The experiment described in this report was named Project Rainout. It was designed to study the behavior of radioiodine deposited on forage as a solution, both with and without the application of additional water. For convenience, the I-tagged solution is referred to as hydrosol, although it technically is a liquid aerosol. The specific objectives of Project Rainout were: 1. To determine the concentrations of 131I on spread alfalfa hay and growing alfalfa as a result of applying the 31I as an aqueous solution. 2. To determine the amounts of 131I in the milk of dairy cows consuming the two types of contaminated forage. 3. To relate the concentration of 131I in forage to that in milk. 4. To study the retention of 131I on growing alfalfa when various amounts of additional water were applied after the initial contamination. ------- PROCEDURES A. Experimental Design The study area for Project Rainout (actual area of the experiment) was a long narrow strip of growing alfalfa between two irrigation laterals at our farm at the Nevada Test Site (Figure 1). The design of the study area was based on feed requirements, forage sampling, hydrosol deposition methods, and various operational requirements (Figure 2). The resulting area was 235 meters long by 5 meters wide having a total area of 1175 square meters. The criteria for deposition of the 131 I solution were: 1. That the study area be uniformly contaminated in a manner simulating a mist or light drizzle. 2. That precipitation levels be on the order of 0. 01 inch. 3. That droplet size be on the order of 70 to 500 microns. 4. That the contamination level be on the order of 105 pCi 131 I/kg of wet forage. 5. That the wind speed be in the range of 1-8 miles per hour, with wind direction unimportant. We felt that the mist or light drizzle criteria, with associated pre- cipitation levels and droplet size, would be optimum for applying contamination, since more, water or larger drops might tend to flood the contamination off the alfalfa. Based on our previous (7 8) experiments * , the above cited forage contamination level would give milk activity levels which could be easily measured. The lactating dairy herd was divided into three groups of six cows each as shown in Table 1. Cow assignments to each group were ------- Barn, Hay Shed, & Corrals -X- Gate 5 , r J Lateral Number 1 ORIGINAL UNCONTAMINATED GREEN CHOP AREA T Reservoir PRJECT "RAINOUT" STUDY AREA X 4 5 Foot Tower SECONDARY UNCONTAMINATED GREEN CHOP AREA 8 X ^__-r_ — Telemetry & Power Poles & Cables -X- 10 ii- ia 14 16 -X- j Scale: 1" = 6O Meters LAYOUT OF EPA EXPERIMENTAL FARM FIGURE 1 4 ------- Lateral #3 Plot 1 Lateral #4 Plot 3 Plot 2 1»21 FTC IT*" __2«J.£ Eao •' Plot 4 Plot 5 >io GREEN CHOP PLOTS Hay Lateral #5 Lateral #6 LEGEND D 1-METER METEOROLOGY STAND El 3-METER METEOROLOGY STAND V AIR SAMPLER - DURING RELEASE T AIR SAMPLER - AFTER RELEASE • PLANCHET NUMBER (ODD NUMBERS ALSO HAD PRECIPITATION MEASUREMENT) Scale: 1" = 30 Meters PROJECT RAINOUT STUDY AREA FIGURE 2 ------- Table 1. Groups of cows and feeding schedule Group Cow No. Type of Feed Remarks II III 12, 13, 16, 18, 27, 28 19, 26, 43 45, 46, 47 2, 5, 11, 15, 21, 44 Contaminated hay (7.5 kg morning and afternoon). Contaminated alfalfa green chop (12. 5 kg - 20 kg morn- ing) and uncontaminated hay (7.5 kg afternoon). Uncontaminated green chop (20 kg morning) and uncon- taminated hay (7.5 kg after- noon) . Fed contaminated hay from afternoon September 29 through afternoon October 6. Fed contaminated green chop from afternoon September 29 through morning October 6, then uncontaminated green chop to the end of the study. Control cows fed green chop from Land #2 - September 29 through October 3. From Land #8, October 4 through October 6. ------- based on a stratified selection made from a list arranged according to the cows' milk production and the number of days in production. This resulted in each group being as nearly the same as possible. The cows in Group I were fed contaminated alfalfa hay each morning and afternoon for eight days. Group II cows were fed freshly chopped contaminated alfalfa forage (hereafter referred to' as green chop) each morning and uncontaminated hay each afternoon for the same period. Group III was the -control group, and these cows were fed uncontaminated green chop in the morning and uncontaminated hay in the afternoon. B. Preparation, Deposition, and Assessment of Hydrosol The hydrosol generation system consisted of a 29-foot, two-inch channel beam suspended about one meter above the ground between two pickup trucks. Twenty-two atomizing spray heads were spaced along the beam at 15-inch intervals. The nozzles of the spray heads pointed up and to the rear so that the axis of o the cone of spray was about 15 above horizontal. A 55-gallon drum in each truck contained the radioiodine solution. Eleven spray heads were fed from each drum. The drums were pres- surized at a constant 40 psi from cylinders of dry nitrogen carried in each truck. Alternate heads had orifices drilled to 1.59mm and 1. 19mm. These delivered, respectively, 0.34 and 0.26 gallons per minute (Figure 3). Twenty-three mCi of 131 I were added to each of the drums, and the drums filled with distilled water. Five grams of potassium iodide carrier and enough 0. 10 N NaOH to maintain the solution at H 8 was added to each drum. The contents of the drums were P thoroughly mixed and aliquots taken to quantitate the true l31 I concentration. ------- oo . - - - * > ^ 1 ' v: •**' AEROSOL SPRAY PROCEDURE FIGURE 3 ------- The tagged hydrosol was sprayed over the study area on Sep- tember 29, 1966. The application was made in a single pass over the area, starting at 1028 hours PDT and taking about 26 minutes. At the end of the contamination run, clean drums were substituted for the contaminated ones and the spray system was flushed before starting the washoff spray. The washoff water was applied by spraying clean tap water over three plots (Plots 1, 2, and 3, Figure 2) after the contaminated spray pass. The vehicles were driven in reverse over all three plots, then forward over 3 and 2, then in reverse again over 2, thus giving three different levels of precipitation on the plots. Plot 4 did not receive any additional precipitation. On Plot 5, the irrigation system was used to add a large amount of water for washoff. This water was added between 1530 hours, September 29, and 1100 hours, September 30. The amount of precipitation was determined from the weight dif- ferences of fifteen plastic petri dishes containing anhydrous calcium sulfate. They were unsealed prior to the spray piiss and resealed with a silicon lubricant as soon as possible after the pass. Thirty 4-inch diameter stainless steel planchets were used to quantitate the deposition of activity on the study area. They were placed on wooden stakes 15" above the ground (the average height of the alfalfa). Whatman 541 filters were placed in these plan- chets following the release to absorb the solution and facilitate drying prior to counting. Gelman "Tempest" air samplers were operated on the anticipated downwind side of the study area during the release (See Figure 2). Following the release, sampler 4 was moved to the opposite side of the area at approximately the same distance from the field as sampler 3. Samplers 1 and 2 were moved to cleared areas near ------- their original positions but within the study area in order to quan- titate the resuspension of radioiodine. The sampling train con- sisted of.a four-inch diameter Whatman 541 prefilter to collect particulate activity and a MSA charcoal cartridge to collect gaseous iodine. Glass slides coated with a phenol red/n-Propanol film were mo- mentarily exposed to the hydrosol by use of a special container. These slides were subsequently used to determine the size and size distribution of the droplets, uncorrected for any spread factor, by measuring the diameter of the characteristic print remaining after the liquid evaporated. A laboratory study was conducted following the field exercise to determine the spread factors. For this study, a vibrating reed was used to generate monodispersed droplets of water. A stroboscope synchronized with the droplet frequency effectively stopped the droplets in space so they could be photographed. The droplets were allowed to impact on glass slides prepared with the phenol red/n-Propanol film and the prints thus formed were compared in size with the size of the droplet recorded on the photo- graph. The procedure was repeated for various sized droplets and a spread factor curve was developed. A more detailed description of these methods is given in a report now in preparation. C. Meteorological Instrumentation Since weather conditions greatly influence the deposition and re- tention of radioactive material, we routinely document the micro- meteorology at the farm during and after a release. For Project Rainout, meteorological instrumentation was installed at the study area as shown in Figure 2. Wind speed and direction instruments, with sensors at a height of one meter, were placed in two locations within the study area. Another wind speed and direction instrument 10 ------- with sensors at three meters was placed at the midpoint and immediately north of the grid. Instrumentation to measure tem- perature, relative humidity, and evaporation was also placed at this point. The wind data were recorded on continuous-trace analog recorder charts. Prior to and during the release the data were integrated and tabulated at one-minute intervals. Following the release and for the next seven days, the data were integrated and tabulated at one-hour intervals. D. Forage Collection and Animal Husbandry The alfalfa hay to be contaminated was placed in the study area in a stack 15 meters long by 5 meters -wide by 24 centimeters deep. The hay was placed on a plastic sheet and covered with screen wire. Following the release, the hay rations (7. 5 kg each) for that day's feeding were weighed into polyethylene feed tubs. The remainder of the hay was collected by weighing feeding rations into plastic bags. The bags were sealed and stored near the corral. Fresh green chop was cut each day. Uncontaminated green chop was cut first, then the contaminated green chop. After cutting the contaminated green chop, the tractor, chopper, and wagon were decontaminated with a high-pressure water spray. The daily ration of contaminated green chop (12. 5 to 20 kg, depending on the amount available) for each cow of Group II was weighed directly into a feed tub from the wagon. The uncontaminated green chop for the con- trol cows was fed free-choice from the feed bunk. Unconsumed contaminated forage was weighed before disposal. This amount was subtracted from the original ration in order to have an 11 ------- accurate record of each cow's consumption. The "uncontaminated" green chop was cut from an area north of the study area for the first five days (Figure 1). When this forage was found to be con- taminated by resuspcnded 131I, the cutting area was moved south of the study area. The Group I and II cows were kept in individual pens at all times except during milking. Each cow had an individual watering bowl, feed tub, and milking bucket. At each milking, the control cows were milked first, followed by the Group I cows, then the Group II cows. The cows of Groups I and II were removed from the individual pens on October 10. They were, however, held as separate groups in divided areas of the corral. Cows of Groups II and III were placed together on October 12. On October 14, all cows of all groups •were turned into a common corral. Blood samples for blood chemistry and hematology were taken from each cow before and after the experiment. The details of animal care, feeding and milking procedures, sampling techniques, record keeping, and equipment decontam- ination are described in References 7 and 9. E. Sampling Techniques Hay and green chop samples were taken from each cow's feed tub. The forage was spread evenly in the tub, and a handful was taken from each surface corner and a handful from the bottom center. The entire sample was sealed in a plastic bag. Milk samples were collected by filling a one-gallon plastic con- tainer (Cubitainer) directly from the milking bucket. After ® filling, the outside of the Cubitainer was rinsed to remove any (R) ' 12 ------- spilled'milk. For composite milk samples, all milk from each cow was poured into a common container and mixed thoroughly and the sample taken from this composite. Grain samples were collected daily from the bulk supply. Water samples were collected daily by filling a Cubitainer from each group's common source. Five samples of growing alfalfa were collected from each of the five treatment areas at each sampling time. Samples were taken by placing a metal ring having an area of 0. 15 m2 in the center of the designated area and cutting all plants within the ring two inches above the ground level. The cut alfalfa was then sealed in plastic bags. F. Sample Analysis The I content of the samples was determined by gamma spec- troscopy. Our system consisted of a TMC Model 404C 400-channel pulse height analyzer. Model 520 P punch control, Model 52Z Resolver-Integrator, Model 500 printer, and a Tally Model 420 perforator. The detectors were two 4 - by 9-inch Nal(Tl) crystals mounted facing each other with vertical spacing variable from direct contact to 14-inch separation. Each crystal had a separate high voltage supply and was viewed by four three-inch photomulti- plier tubes. The crystal assembly was mounted in a steel shield with six-inch walls. The inside dimensions of the shield were 39-by 42- by 42-inches, and it was lined with lead, cadmium, and copper sheets. Table 2 shows the types of sample containers used and the mini- mum sensitivity for each type sample. The minimum sensitivity was based on a 40-minute count and average sample size. The 13 ------- resolution of the system was 10. 2% based on the 137 Cs photopeak. Table 2. System efficiency and minimum sensitivity for 131I Sample type Milk and water Grain Hay Charcoal (from air sampler) Green chop Filter paper Fallout planchet Container 4-liter Cubi- tainer 400-ml plastic 400-ml plastic 400-ml plastic 400-ml plastic 400-ml plastic 400-ml plastic Efficiency 17. 3% 27.8% 28. 1% 27. 8% 34. 8% 48. 0% 48. 0% Minimum Sensitivity* 10+_5 pCi/1 80+10 pCi/kg 100+15 pCi/kg 30+5 pCi/sample 80+10 pCi/kg 15+5 pCi/sample 15+5 pCi/sample *Based on a 40-minute count. 14 ------- RESULTS AND DISCUSSION A. Deposition and Assessment of Radioiodine Solution Of the 46 mCi of 131I in the drums, 44. 3 mCi were sprayed out. At the end of the contamination run, four gallons of solution re- mained in the drums. The fallout planchets showed an average activity deposition of 24. 6 (o,Ci/m2 (Table 3). Using this figure, we calculated that 28. 9 mCi, or 65. 2% of the 131I released, was deposited on the study area. This contamination was deposited with an average of 0. 007 inches of precipitation on the study area (Table 4). Two planchets had extreme deposition values which can be explained. The high deposition of 55. 29 |J.Ci/m2 at No. 4 was due to a stop for sprayer adjustments at this point. The low deposition of 3.82 [xCi/m at No. 27 was probably due to sputtering of the spray caused by movement of the solution in the nearly empty tanks. After deleting these two values, the activity deposition varied by a factor of about 4 (10.58 to 45.64 u.Ci/m2). This variation is attributed to variable wind speed and direction (Table 5), and uneven ground speed of the trucks carrying the spraying system. The levels of uncontaminated precipitation for the washoff study were: Plot 1 - 0.003" Plot 4 None Plot 2-0. 041" Plot 5-8. 23" Plot 3 - 0.032" 15 ------- Table 3. 131I deposition on planchets Sample Position 1 2 3 4 5- 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Activity ((j-Ci/m2 ) 32. 02 17-48 29. 11 55. 29 22.96 15. 24 24.76 24.76 38. 54 11. 69 22. 01 19. 10 19. 78 45. 64 22. 20 * 39.97 20. 22 27. 04 22. 37 28.93 30.76 25.96 :,'= 17.80 16. 32 3.82 25.96 16 ------- Table 3. I deposition on planchcts (Continued) Sample Position Activity 29 10.58 30 18.81 Average = 24. 6 + 10.6 *Planchet dropped from stake **Mean + one standard deviation 17 ------- Table 4. Amount of precipitation at each sample position Sample Position Precipitation (inches) 1 0.009 2 0.010 3 * 4 0. 007 5 0.012 6 0. 006 7 0. 005 8 0.008 9 0.015 10 0.006 11 0.008 12 0. 007 13 0.003 14 0.001 15 0.003 Average - 0. 007 +_ 0. 004 inches** * Sample dropped from stake -f-'f Mean + one standard deviation The data from the four air samplers (Table 6) indicate some resus- pension of activity after the deposition. The ratios of gaseous-to- particulate activity generally increased during the afternoon and correlate roughly with temperature rise. This is attributed to volatilization and/or transpiration of the iodine from the plants. Figure 4 is a histogram showing the distributioTT of droplet sizes, uncorrected for the spread factor. The curve does not represent a statistical best fit, but only implies an outline of the distribution. A log-normal distribution of the droplet size has a geometric mean of 283 (J. and a geometric standard deviation of 2. 05. When the spread factor is applied to the size distribution, the geometric mean is reduced to 139 JJL. 18 ------- Table 5. Meteorological data during and after deposition September 29, 1966 Time (PDT) lozsW 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 10.50. 1051 1052 1053 East 1 Meter Dir* Speed** 060 085 090 085 050 045 045 050 080 095 ,075 060 065 070 085 080 080 075 055 055 055 065 060 045 040 045 07 07 05 06 08 07 05 04 06 08 08 07 06 04 05 05 05 06 06 07 08 07 06 06 06 06 West 1 Meter Dir* Speed** 070 090 070 050 055 035 050 090 090 085 070 075 085 070 070 085 050 060 060 070 065 065 070 060 055 080 05 06 06 04 04 06 05 05 05 05 06 06 07 06 05 04 05 04 04 07 07 08 07 07 07 07 3 Meters Dir* Speed** 030 040 060 090 030 050 045 050 030 035 075 085 080 055 055 060 070 070 060 075 055 045 040 045 060 060 09 09 09 07 07 09 09 07 07 07 09 11 1 1 10 09 07 07 07 06 09 09 08 12 11 10 10 Temperature Rel.Hum. °F Percent 74 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 27 27 27 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 29 29 29 29 29 29 29 19 ------- Table 5. Meteorological September 29, data during and after deposition 1966 (Continued) Time (PDT) 1054(2) 1055 1056 1057 1058 1059 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 East 1 Meter Dir* Speed** 040 065 075 085 085 090 090 090 180 200 160 190 185 190 255 315 315 325 335 05 07 06 06 07 08 05 05 06 06 04 05 06 05 02 02 03 03 03 West 1 Meter Dir* Speed** 070 085 090 080 075 085 065 090 170 215 160 170 180 180 160 315 320 315 330 04 05 05 06 06 05 05 05 05 04 06 07 06 03 02 02 02 02 02 3 Meters Dir* Speed** 040 035 055 035 035 060 065 090 180 215 OUT OUT OUT OUT OUT OUT OUT OUT OUT 10 08 09 08 10 08 08 07 08 08 06 07 10 08 04 02 04 05 05 Temperature Rel.Hum. °F Percent 75 75 75 75 75 75 75 77 80 80 78 78 74 72 67 63 60 58 58 29 29 29 29 29 29 29 29 27 29 28 29 29 30 35 37 39 40 41 *Azimuth wind is blowing **Miles per hour (1) Start of Deposition (2) End of Deposition from 20 ------- Table 6. Air sampler data during and after deposition Sampler Time Collected 1 1130<2) 1230 1340 1450 1550 1650 2 1130<2) 1230 1340 1450 1550 1650 3 1130(2)- 1230 1340 1450 1550 1650 4 1130<2) 1230 1340 1450 1550 1650 Total Activity^) (pCi) 3.80xl04 1. 19xl05 1. 07x1 04 1.92xl04 5. 14xl03 4.44xl03 2. 61xl04 3.41xl04 . 3. 33xl03 8. OSxlO3 6.89xl03 7. 28xl02 3. 68xl03 3. 53xl02 4. 05x10* 8. 16X101 2. 13xl02 7.42X101 3. 67X101 1. 55xl04 1. I6xl04 5.85xl03 3. 31xl03 3. 12xl03 Char coal /Prefilter Ratio 3. 2 17-3 13.4 13.7 10.8 6. 2 2.9 10.8 10.8 11.0 30. 6 17.3 2.6 4. 3 N.A.O) N.A.(3) 0. 2 N.A.<3) 22. 0 5.2 7.7 6.7 5. 3 12.7 (1) Total of prefilter and charcoal cartridge activities. (2) These samples collected during and immediately after deposition. (3) Filter activity was non-detectable. 21 ------- 63 163 263 363 463 SIZE (Microns) 563 663 763 863 HISTOGRAM OF DROPLET SIZE DISTRIBUTION FIGURE 4 22 ------- B. Effective Half-life on Growing Alfalfa The means of the 131I concentrations in the five samples collected from each of the five plots at each sampling period are plotted in Figure 5. The effective half-life, based on the best-fit regression line from the mean values from all five plots, was 7. 0 + 0. 7 days. * Statistical analysis indicates that the addition of various amounts of water after contamination did not affect the decrease of activity with time. The decrease of activity with time did not follow a simple exponential function. Future investigations are planned in an attempt to explain this. C. 131 I Activity in Dairy Cow Forage The daily averages of I concentrations in green chop and hay are summarized in Table 7. The peak activity level of 2. 1 x 107 pCi/kg in green chop was obtained on the day after the release while the peak of 9. 8 x 106 pCi/kg in hay occurred on the afternoon of the day of release. The daily averages of I in green chop and hay are plotted in Figures 5 and 6 respectively. The effective half-life in green chop was 4.5+^1.6 days, and in hay, 3. 6 +_ 0. 9 days. These half-lives were calculated on the basis of a best fit regression 'line. Since the hay was bagged and sealed shortly after contamination, the short (3.6 days) half-life is puzzling. The rapid loss of 3 I apparently was due to evaporation from the hay and the ultimate escape of the 131I vapor through punctures in the bag or through the plastic itself. The variation in effective half-life on gro-wing alfalfa (7. 0 days) and green chop (4. 5 days) is probably due to adsorption of activity on the chopping machinery. In both types of forage, a rise in activity levels occurred toward *Mean + one standard deviation. Z3 ------- H r (D UJ IT O O) jc O a s io7 Teff = 7.O days ± O.7 • PLOT 1 A PLOT 2 » PLOT 3 - • PLOT 4 PLOT 5 10 12 14 16 18 20 22 24 26 28 30 DAYS AFTER DEPOSITION MEAN CONCENTRATIONS OF 131I IN GROWING ALFALFA FIGURE 5 ------- Table 7. Summary of the daily averages of 131I concentrations (H-Ci/kg) on forage Collection Date 9/29 9/30 10/1 10/2 10/3 10/4 10/5 10/6 *Mean - Time Green Chop p.m. 19 12* a. m. 21 +. 1 p. m. a.m. 17+3 p. m. a.m. 11 13 p. m. a.m. 6.813.3 p.m. a.m. 5. 2 1 2. 7 p. m. a.m. 12 1 1 p. m. a.m. 8.010.4 p. m. f- one standard deviation. Hay 9.8 1 5.8 1 4. 0 1 3.0 +_ 3.4 1 1.6 1 1.71 2. 0 1 0.99 1 2. 0 1 2. 3 + 1.81 2.2 1 1.71 1.4 + 7. 1* 3. 7 2.3 2.9 3. 7 1.8 1. 1 1.8 0.85 1.6 2.6 1. 3 1.4 0.5 1. 1 25 ------- Teff = 4.5 days ± 1.6 456789 DAYS AFTER DEPOSITION 131 MEAN VALUES OF IJII IN GREEN CHOP FIGURE 6 26 ------- 3 — 2 — Teff = 3.6 days ± O.9 I I t I I I 10 45678 DAYS AFTER DEPOSITION 11 12 131 MEAN VALUES OF 1JII IN HAY FIGURE 7 27 ------- the end of the feeding period. This rise is especially sharp in the green chop. As with the other erratic values discussed previously, no logical explanation except uneven deposition over the study area can be offered for this. The intended uncontaminated green chop was found to have low level contamination due to the resuspension of activity. Concentrations of 4. 3 x 104 pCi/kg were detected on the day after the deposition. After the eighth day, when the "uncontaminated" green chop was being fed to the Group II cows, the 13 I concentration did not exceed 2. 7 x 103pCi/kg. Since this was three orders of magnitude below the lowest value on contaminated green chop, it could not have contributed more than 0. 1% to the cows' intake of 131I. Activity levels slightly above the minimum detectable were found in some grain and water samples, but these were also considered insignificant. D. 131 I Activity in Milk The mean values of I in the milk of Groups I and II are shown in Table 8. The same data are presented graphically in Figures 8 and 9. Data for Group III cows are not included as they are con- sidered controls and do not add significantly to the discussion. The levels of 31I in the milk from both groups of cows rose toward the end of the feeding period, giving a double peak effect in the curves. These secondary peaks follow the peaks of the for- age curves very closely, and the increased milk activities are attributed largely to the combination of increased forage activity concentrations and increased forage consumption. Toward the end of the feeding period, the Group II rows were eating a larger amount of more highly contaminated forage; apparently the green chop was more palatable because of more succulent growth during the latter stages of the study. 28 ------- Table 8. Mean concentrations of 131I (pCi/liter) in milk by groups Date 9/29 9/30 10/1 . 10/2 10/3 10/4 10/5 10/6 10/7 10/8 10/9 10/10 Time P- a. P- a. P- a. P- a. P- a. P- a. P- a. P- a. P- a. P- a. P- a. P- m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. m. Group 1. 9. 1. 1. 1. 7- 6. 5. 6. 5. 6. 6. 7- 8. 8. 8. 6. 2. 1. 9. 7. 4. 4. 6xl04 5xl04 3xl05 2xl05 IxlO5 2xl04 5xl04 6xl04 OxlO4 5xl04 4xl04 8xl04 6xl04 5xl04 8x1 04 IxlO4 7x1 O4 7x1 04 8xl04 2xl03 2xl03 2xl03 2xl03 I (Hay) + + + + + + + + + + + + •f + + + + + + + + + + I- 5. 0. 0. 0. 3. 1- 1. 1. 1. 1. 2. 2. 2. 3. 3. 1. 0. 0. 1. 2- 1. 1. 6* 6 7 6 6 0 8 1 3 4 9 6 5 8 7 1 8 6 3 9 0 4 4 Group II (Green 1. 4. 8. 5. 8. 5. 7. 5. 6. 4. 6. 3. 7. 4. 7. 5. 4. 2. 1. 8. 6. 5. 3. 6xl05 5xl05 6xl05 3xl05 IxlO5 9xl05 7xl05 3xl05 IxlO5 7xl05 IxlO5 7xlOs 5xlOs 7xl05 8xl05 6xl05 2xl05 IxlO5 7xl05 5xl04 8xl04 4xl04 3xl04 + 0. + 1. + 1. + 1. + 1. + 1. + 1. + 2. + 1. + 1. + 2. + 1. + 1. + 1. + 2. + 1. + 1. + 0. + 0. + 3. + 3. + 2. + 1. Chop) 5=:= 1 8 2 5 1 5 1 8 7 3 3 9 1 0 2 3 7 8 7 4 0 7 29 ------- Table 8. Mean concentrations of 131i in milk by groups (pCi/litcr) (Continued) Date Time 10/11 a.m. p. m. 10/12 a.m. p. m. 10/13 a.m. p. m. 10/14 a.m. 10/15 a.m. 10/16 a.m. 10/17 a.m. 10/18 a.m. 10/19 a.m. 10/20 a.m. 10/21 a.m. 10/22 a.m. 10/24 a.m. 10/26 a.m. 10/28 a.m. 2. 1. 1. 7. 5. 5. 5. 3. 4. 2. 2. 2. 4. 1. 1. 2. 1. 1. Group I (Hay) OxlO3 +0.7 6xl03 + 0. 5 OxlO3 +0.4 8xl02 ** 6xl02 8xl02 IxlO2 IxlO2 SxlO2 9xl02 4xl02 SxlO2 2X101 7xl02 4xl02 SxlO1 4xl02 6xl02 Group II (Green Chop) l.SxlO4 1.4xl04 7. IxlO3 7- OxlO3 3. 6xl03 3. IxlO3 2. 6xl03 2.2xl03 1. 6xl03 1. 3xl03 1. 2xl03 l.OxlO3 6. 6xl02 6. 5xl02 6.7xl02 4. 3xl02 4. 9xl02 3.9xl02 + 0.8 + 0.8 + 3.9 + 3. 2 + 1.7 + 1.2 + 0.9 + 0. 3 + 0.4 + 0.4 + 0.4 + 0.6 + 3. 1 + 1.6 + 1.8 + 3.0 + 1.9 + 1.0 •'-'Mean + one standard deviation reported. ':*Milk from all cows in this group was composited from this date on. 30 ------- 10* 1 r i 1 1 r • Last Feeding of Contaminated Hay 1 1—=1 -i Teff = 2.5 days ± O.4 UL UJ 10 O a Teff = O.94 days ± O.O4 10 Teff = 5.6 days ± 2.4 10 1 I I I L l I I L J L J I I I L 02468 10 12 14 16 18 20 DAYS AFTER DEPOSITION 22 24 26 28 30 MEAN CONCENTRATIONS OF 131I IN MILK OF GROUP I COWS FIGURE 8 ------- io 10 Contaminated Green Chop i—r i—i—i 1—i—r i \ Teff = O.86 days ± O.O2 n 1 1 1 1 r 12 14 16 18 20 DAYS AFTER DEPOSITION 22 24 26 28 30 MEAN CONCENTRATIONS OF 131I IN MILK OF GROUP II COWS FIGURE 9 ------- The nature of the feed data precludes a calculation of a meaningful effective half-life in the milk during the feeding period. Therefore, a reasonable approach is to calculate the effective half-lives from the peak milk to the valley of the double peak. Effective half-lives were also calculated for two distinct periods after the end of feeding. These half-lives are shown in Table 9. Table 9. Effective half-lives of 131I in milk Days after start Group I Cows Group II Cows of feeding (Hay) (Green chop) 2nd through 6th 2. 5 +_ 0. 4 days 7. 9 +_ 4. 3 days 10th through 15th 0.94 + 0.04 0. 86 +_ 0. 02 16th through 28th 5.6 + 2.4 5. 1 +_ 0. 5 In Table 10 the results of this study are compared with the results from three of our previous studies. Projects Hayseed and (8) Alfalfa were controlled releases of 131I-tagged dry aerosols over grass or alfalfa-grass forage at our farm. We also con- ducted a field study at two commercial dairies following the Pike Event , an underground nuclear test which produced an inad- vertent release of fission products to the atmosphere. During feeding, the'effective half-life in milk from hay fed cows was close to that found on Hayseed, but considerably less than those from Alfalfa and Pike. For green chop fed cows, the effective half-life was two to three times that found in previous studies. After feeding of contaminated forage stopped, the half-lives were in reasonable agreement with those reported in the literature. In both groups, the peak milk value occurred on the afternoon of the second day of feeding or about 24 hours after ingestion of the first contaminated feed. This is in reasonable agreement with 33 ------- Table 10. Comparison of results from four studies Study Type of Type of Contamination Green Chop Pike Fission Alfalfa March Products 1964 Hayseed 13 ^-Tagged Sudan October Aerosol Grass 1965 (23 uCMD) Alfalfa 131I-Tagged Alfalfa- June Aerosol Oats 1966 (2 (J.CMD) Rainout 131 1 Solution Alfalfa October 1966 Forage Peak Average Concentration (pCi/kg) Green Chop Hay 4.7xl03 1.3xl03 2.7xl06 4. IxlO5 3.4xl06 5.6xl05 2. IxlO7 9. 8xl06 Milk Peak Average ^eff During Time to Peak Concentration (pCi/liter) Feeding (Days) (Days) Green Chop Hay Green Chop Hay Green Chop Hay 3.8xl02 7-OxlO1 3.8 5.9 4 3 2.2x10" l.lxlO4 3.0 2.7 2 1 l.OxlO5 3.9xl04 2.5 8.2 1.5 1 8.6xl05 1.3xl05 7.9 2.5 1 1 Peak Milk (pCi/1) Peak Forage(pCi/kg) Green Chop Hay 0.080 0.054 0.008 0.027 0.029 0.069 0.041 0.013 ------- our other experiments. The ratios of peak average milk activity to peak average forage activity were 0. 013 for the cows fed hay and 0. 041 for the cows fed green chop. This indicates that for this type of contamination and forage, radioiodine is more biologically available from alfalfa green chop than it is from hay. The same trend was observed with actual fallout from Pike, but the reverse case was true on Hayseed and Alfalfa, where the milk/forage ratios were higher for the hay cows. Table 11 shows the percent of the total 131I ingested which was secreted in milk. The cows which ate hay secreted 4. 5 + 1. 5% of the total 31I ingested, while those which ate green chop secreted 6. 1 + 1.4%. While this would also indicate a greater biological availability of iodine on green chop, there is no signi- ficant difference between the two percentages. The ratio of maximum milk concentration to minimum milk concen- tration at each milking was calculated. The mean of these maximum/ minimum ratios was 2. 98 + 2. 24 for Group I and 2. 86 jf 0. 96 for Group II. This is a measure of the variability between cows as a herd and as groups. 35 ------- Table 11. Percent of 3 11 ingested which was secreted in milk Co-w Group No. II 19 (Green 26 Chop) 43 45 46 47 Total [o.Ci Total p.Ci Percent Mean -f One Ingested Secreted Secreted Standard Deviation I (Hay) 12 13 16 18 27 28 292.5 302. 3 251.0 289. 1 376.7 322.0 19. 1 14.4 13.7 7. 3 16. 0 10. 6 6. 5 4.8 5. 5 2.5 4.2 3. 3 4.5 + 1.5% 1320. 5 1011.8 1474.6 1648.2 1561.8 1472.8 63. 5 72.7 88. 6 71. 5 126. 2 96. 0 4. 8 7- 1 6.0 4. 3 8. 1 6.5 6.1 + 1.4% 36 ------- CONCLUSIONS When radioiodine is deposited on forage (growing alfalfa and hay) in an aqueous solution under the conditions of this experiment, the following conclusions concerning the transfer of the radioiodine to cow's milk may be drawn: J_. I on fresh green chop appeared to be more biologically available than it was on hay. Zj. Following ingestion of the contaminated forage, the peak activity concentration in milk (pCi/liter) occurred in about one day. This concentration was one to two orders of magni- tude lower than the peak concentration in the forage (pCi/kg). 3. After ingestion of the contaminated forage was stopped, the effective half-life of 131I in milk was about one day for the first six days, then about five days until negligible con- centrations were reached. 4. Dairy cows eating contaminated green chop secreted 6. 1% of the ingested 131I in their milk, while those eating contami- nated hay secreted 4. 5%. 5. Although it appeared that there was no washoff effect, the statistical design of the washoff experiment was not sufficient to allow any definite statements about the effect of additional precipitation. However, the effective half-life of I on growing alfalfa was about seven days. 37 ------- REFERENCES 1. D. S. Earth and J. G. Veater, Dairy farm radioiodine study following the Pike Event, Report T1D-21764, November 1964. 2. Radioiodine study in conjunction with Project Sulky, Southwestern Radiological Health Laboratory Report SWRHL-29r, May 1966. 3. S. C. Black, D. S. Earth, R. E. Engel and K. H. Falter, Radio- iodine studies following the transient nuclear test (TNT) of a KIWI reactor, Southwestern Radiological Health Laboratory Report SWRHL-26r, May 1969. 4. S. C. Black, R. E. Engel, V. W. Kandecker and D. S. Earth, Radioiodine studies in dairy cows following Project Palanquin, Southwestern Radiological Health Laboratory Report PNE-914F, in press. 5. D. S. Earth, R. E. Engel, S. C. Black and W. Shimoda, Dairy farm studies following the Pin Stripe event of April 25, 1966, Southwestern Radiological Health Laboratory Report SWRHL-41r, July 1969. 6. R. L. Douglas, Status of the Nevada Test Site experimental farm, Southwestern Radiological Health Laboratory Report SWRHL-36r, January 1967. 7. S. C. Black, D. S. BarthandR. E. Engel, Iodine-131 dairy cow uptake studies using a synthetic dry aerosol (Project Hayseed), Southwestern Radiological Health Laboratory Report SWRHL-28r, in press. 8. R. E. Stanley, S. C. Black and D. S. Earth, Iodine-131 dairy cow studies using a dry aerosol (Project Alfalfa), Southwestern Radiological Health Laboratory Report SWR1IL-4 2r, August 1969. 9. D. D. Smith and R. E. Engel, Progress report for the Eioenviron mental Research Part I; Experimental dairy herd, Southwestern Radiological Health Laboratory Report SWRHL-55r, March 1969. 38 ------- DISTRIBUTION 1 - 20 SWRHL, Las Vegas, Nevada 21 Robert E. Miller, Manager, NVOO/AEC, Las Vegas, Nevada 22 Robert H. Thalgott, NVOO/AEC, Las Vegas, Nevada 23 A. Dean Thornbrough, NVOO/AEC, Las Vegas, Nevada 24 Henry G. Vermillion, NVOO/AEc, Las 'Vegas, Nevada 25 Robert R. Loux, NVOO/AEC, Las Vegas, Nevada 26 Donald W. Hendricks, NVOO/AEC,' Las Vegas, Nevada 27 Elwood M. Douthett, NVOO/AEC, Las Vegas, Nevada 28 Jared J. Davis, NVOO/AEC, Las Vegas, Nevada 29 Ernest D. Campbell, NVOO/AEC, Las Vegas, Nevada 30 - 31 Technical Library, NVOO/AEC, Las Vegas, Nevada 32 Mail & Records, NVOO/AEC, Las Vegas, Nevada 33 Chief, NOB/DASA, NVOO/AEC, Las Vegas, Nevada 34 Martin B. Biles, DOS, USAEC, Washington, D. C. 35 Roy D. Maxwell, DOS, USAEC, Washington, D. C. 36 Assistant General Manager, DMA, USAEC, Washington, D. C. 37 Gordon C. Facer, DMA, USAEC, Washington, D. C. 38 John S. Kelly, DPNE, USAEC, Washington, D. C. 39 Fred J. Clark, Jr., DPNE, USAEC, Washington, D. C. 40 Daniel W. Wilson, Div. of Biology & Medicine, USAEC, Washington, D. C. 41 John R. Totter, DBM, USAEC, Washington, D. C. 42 Joseph J. Di Nunno, Office of Environmental Affairs, USAEC, Washington, D. C. 43 Philip Allen, ARL/NOAA, NVOO/AEC, Las Vegas, Nevada 44 Gilbert J. Ferber, ARL/NOAA, Silver Spring, Maryland 45 John S. Kirby-Smith, DBM, USAEC, Washington, D. C. 46 Charles L. Osterberg, DBM, USAEC, Washington, D. C. 47 Rudolph J. Engelmann, DBM, USAEC, Washington, D. C. 48 L. Joe Deal, BBM, USAEC, Washington, D. C. 49 Joseph A. Lieberman, Act.Comm., Radiation Office, EPA, Rockville, Md. 50 William A. Mills, Act.Dir., Div. of Research, Radiation Office, EPA, Rockville, Maryland 51 - 52 Charles L. Weaver, Act.Dir., Div. of Surveillance & Inspection, Radiation Office, EPA, Rockville, Maryland ------- Distribution (continued) 53 Bernd Kahn, Radiological Engineering Lab., EPA, Cincinnati, Ohio 54 Interim Regional Coordinator, Region IX, EPA, San Francisco, Calif. 55 Southeastern Radiological Health Lab., EPA, Montgomery, Alabama 56 William C. King, LRL, Mercury, Nevada 57 Bernard W. Shore, LRL, Livermore, Calif. 58 James E. Carothers, LRL, Livermore, Calif. 59 Roger E. Batzel, LRL, Livermore, Calif. 60 Lynn R. Anspaugh, LRL, Livermore, Calif. 61 Howard A. Tewes, LRL, Livermore, Calif. 62 Lawrence S. Germain, LRL, Livermore, Calif. 63 Paul L. Phelps, LRL, Livermore, Calif. 64 Harry J. Otway, LASL, Los Alamos, New Mexico 65 William E. Ogle, LASL, Los Alamos, New Mexico 66 William L. Langham, LASL, Los Alamos, New Mexico 67 Harry S. Jordan, LASL, Los Alamos, New Mexico 68 Arden E. Bicker, REECo, Mercury, Nevada 69 Clinton S. Maupin, REECo., Mercury, Nevada 70 Byron F. Murphey, Sandia Laboratories, Albuquerque, New Mexico 71 Melvin L. Merritt, Sandia Laboratories, Albuquerque, New Mexico 72 Richard S. Davidson, Battelle Memorial Institute, Columbus, Ohio 73 R. Glen Fuller, Battelle Memorial Institute, Las Vegas, Nevada 74 Steven V. Kaye, Oak Ridge National Lab., Oak Ridge, Tenn. 75 Robert H. Wilson, University of Rochester, New York 76 Leo K. Bustad, University of California, Davis, Calif. 77 Leonard A. Sagan, Palo Alto Medical Clinic, Palo Alto, Calif. 78 Vincent Schultz, Washington State University, Pullman, Washington 79 Arthur Wallace, University of California, Los Angeles, Calif. 80 Wesley E. Niles, University of Nevada, Las Vegas, Nevada 81 Robert C. Pendleton, University of Utah, Salt Lake City, Utah 82 William S. Twenhofel, U. S. Geological Survey, Denver, Colo. 83 Paul R. Fenske, Teledyne Isotopes, Palo Alto, Calif. 84 - 85 DTIE, USAEC, Oak Ridge, Tennessee(for public availability) ------- |