Milk Transfer Coefficient Research Articles

Doses from external irradiation and ingestion of 134Cs, 137Cs and 90Sr of the population of Belarus accumulated over 35years after the Chernobyl accident.

This study considers the exposure of the population of the most contaminated Gomel and Mogilev Oblasts in Belarus to prolonged sources of irradiation resulting from the Chernobyl accident. Dose reconstruction methods were developed and applied in this study to estimate the red bone-marrow doses (RBMs) from (i) external irradiation from gamma-emitting radionuclides deposited on the ground and (ii) 134Cs, 137Cs and 90Sr ingestion with locally produced foodstuffs. The mean population-weighted RBM doses accumulated during 35years after the Chernobyl accident were 12 and 5.7mGy for adult residents in Gomel and Mogilev Oblasts, respectively, while doses for youngest age groups were 20-40% lower. The highest mean area-specific RBM doses for adults accumulated in 1986-2021 were 63, 56 and 46mGy in Narovlya, Vetka and Korma raions in Gomel Oblast, respectively. For most areas, external irradiation was the predominant pathway of exposure (60-70% from the total dose), except for areas with an extremely high aggregated 137Cs soil to cow's milk transfer coefficient (≥ 5.0Bq L-1 per kBq m-2), where the contribution of 134Cs and 137Cs ingestion to the total RBM dose was more than 70%. The contribution of 90Sr intake to the total RBM dose did not exceed 4% for adults and 10% for newborns in most raion in Gomel and Mogilev Oblasts. The validity of the doses estimated in this study was assessed by comparison with doses obtained from measurements by thermoluminescence dosimeters and whole-body counters done in 1987-2015. The methodology developed in this study can be used to calculate doses to target organs other than RBM such as thyroid and breast doses. The age-dependent and population-weighted doses estimated in this study are useful for ecological epidemiological studies, for projection of radiation risk, and for justification of analytical epidemiological studies in populations exposed to Chernobyl fallout.

Environmental transfer parameters of strontium for soil to cow milk pathway for tropical monsoonal climatic region of the Indian subcontinent

The radionuclide transfer between compartments is commonly described by transfer parameters representing the ratio of concentrations of an element in two compartments for equilibrium conditions. This is a comprehensive study on the soil-to-grass transfer factor (Fv) and grass-to-cow milk transfer coefficient (Fm) for stable strontium (Sr) for soil-grass (pasture)-cow (Bos taurus) milk environmental pathway under field conditions for a high rainfall tropical monsoonal climatic region of the Indian subcontinent. The study was conducted in the vicinity of the Kaiga nuclear power plant (NPP), situated ~ 58 km inland of the West Coast of the Indian subcontinent. A grass field was developed exclusively for this study, and two cows of the native breed were raised to graze on it. The soil, grass, and milk were analyzed to evaluate the Fv and the Fm values for the stable Sr. For comparison, several pasture lands and the cows raised by the villagers and a dairy farm were also studied. The Fv values were in the range 0.18—8.6, the geometric mean (GM) being 1.8. The correlations of Fv values with a range of physicochemical parameters are presented. The GM values for Fm were 2.2 × 10–3 d L-1 and 7.2 × 10–3 d L-1 for the two cows raised for this study, 2.6 × 10–3 d L-1 for those raised by the villagers, and 4.2 × 10–3 d L-1 for the dairy farm. The site-specific Fm value for the region was determined as 3.2 × 10–3 d L-1. The concentration ratio (CR), defined as the ratio of Sr concentration in milk to that in feed under equilibrium conditions, exhibited less variability (1.8 × 10–2—5.4 × 10–2) among the three categories of cows.

Grass to cow milk transfer coefficient (Fm) of Iodine for equilibrium and emergency situations

Radioiodine ( 131 I) is one of the radionuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. If released to the environment during an accident, 131 I may enter the grass→cow→cow milk pathway, leading to increased thyroid dose to those consuming milk, especially infants and children. The estimation of site-specific grass to milk transfer coefficient (F m ) for iodine is essential for an accurate assessment of the radiological hazard to the population in the region surrounding a nuclear power plant. In this study, a method based on the chemical separation of iodine present in grass and cow milk, and subsequent neutron activation analysis (NAA) has been optimized for the determination of stable iodine concentration in grass and cow milk. The method involves preconcentration of iodine from the sample matrix, and determination of iodine by NAA. The detection limit of stable iodine in milk was found to be 1 ng/mL. For the validation of the result, iodine concentration in NIST reference materials was determined simultaneously. The present study has yielded a F m value of 5.6 × 10−3 d/L for dairy farm cows and 6.3 × 10−3 d/L for local breed cows under equilibrium conditions. These results are similar to the values given in International Atomic Energy Agency report (TRS-472). To simulate a rapid deposition of iodine on grass and for the estimation of F m value for an emergency situation, grass grown in the experimental field was sprayed with stable potassium iodide solution and fed to the adopted cows, and the milk samples were collected regularly and analyzed. The F m value for the simulated accidental situation was found to be 3.9 × 10−3 d/L.

Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region

Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of 137Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the 137Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10−1 and 1.8 × 10−1 for 137Cs and stable Cs, respectively. The Fm of 137Cs had geometric mean values of 1.9 × 10−2 d L−1 and 4.6 × 10−2 d L−1, respectively, for adopted Cows 1 and 2; 1.7 × 10−2 d L−1 for the cows of local farmers, and 4.0 × 10−3 d L−1 for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of 137Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for 137Cs and stable Cs and their dependence on the potassium content (40K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of 137Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 μSv y−1 and 0.04 μSv y−1,while that to an adult were 0.39 μSv y−1 and 0.05 μSv y−1, respectively.

Estimation of grass to milk transfer coefficient for cesium for emergency situations

The grass to milk transfer coefficient is usually represented as F m values. This paper reports the results of grass to cow milk transfer coefficients (F m ) for Cesium for emergency situation. An experimental grass field was developed in Kaiga region and two cows were adopted for collecting milk samples regularly. Grass was cut from the field and spiked with very low concentration of Cs (in the form of CsCl or CsI), to simulate a sudden deposition of Cs on grass and fed to the adopted cows. The milk samples were collected during normal milking periods (morning and evening) for several days and analyzed. The peak concentration of Cs in milk was observed during time period 24-36 hrs after the intake of spiked grass. Three spike experiments were carried out and values of F m were found to be 7.8 × 10 -3 d L -1 , 3.5×10 -3 d L -1 and 2.4×10 -3 d L -1 . The grass to milk transfer coefficient values observed under spiked conditions were an order of magnitude lower when compared to the equilibrium transfer coefficient for Kaiga region, which highlights the importance of studies aimed at generating site-specific database on F m for simulated emergency situation.

The transfer of 239/240Pu to cow milk

In summer 1993 we measured the transfer of 239/240Pu to milk from herbage from a pasture located 5 km from the Chernobyl nuclear power plant. In one treatment cows were allowed to graze freely on the pasture. In a second treatment, cows were fed herbage collected from the pasture in stalls. The milk transfer coefficient; F m did not vary significantly between treatments and the mean value of 7.5 × 10 −6 d l −1 was higher than previously reported values. Despite many values of F m for Pu in the literature we identified few relevant original data sets. Transfer coefficient values for Pu are only appropriate when used in conjunction with a specified time period or an appropriate model which allows for the biological half-life. We recommend for screening purposes an F m value of 1 × 10 −5 d l −1 for Pu, with an order of magnitude lower value being appropriate for cows which are only exposed for one grazing season.

137Cs and 90Sr transfer to milk in Austrian alpine agriculture

The alpine regions of Austria were among the most contaminated territories outside of the former USSR after the Chernobyl accident. In the investigated province of Salzburg the median 137Cs surface deposition was 31.4 kBq m −2 with maximum values exceeding 90 kBq m −2 (May 1986). To quantify the transfer of 137Cs and 90Sr from vegetation to milk in these seminatural conditions nine seasonally grazed alps were identified and vegetation and milk sampled during summer 2002 and summer 2003. Mean ± SD milk transfer coefficients (fm) for 137Cs and 90Sr were 0.0071 ± 0.0009 d l −1, and 0.0011 ± 0.0004 d l −1, respectively; which for 137Cs is markedly higher than those fm values found in intensive agricultural systems. Transfer kinetics for 137Cs into cow milk were approximated using a 2-compartment model with a short and a long-term component. Fitting the model to empirical data results in reliable estimates of the time constant of the short-term component, biological half-life 1.06 ± 0.28 d, whereas the estimates of the long-term component are subject to high uncertainties.

CREDIBILITY OF UNCERTAINTY ANALYSES FOR 131I PATHWAY ASSESSMENTS

We would like to make your readers aware of numerous concerns we have with respect to the paper by A. A. Simpkins and D. M. Hamby on Uncertainty in transport factors used to calculate historic dose from 131I releases at the Savannah River Site. The paper by Simpkins and Hamby concludes by saying their uncertainty analysis would add credibility to current dose reconstruction efforts of public exposures to historic releases of 131I from the operations at the Savannah River Site, yet we have found their paper to be afflicted with numerous errors in assumptions and methodology, which in turn lead to grossly misleading conclusions. Perhaps the most egregious errors are their conclusions, which state that: a. the vegetable pathway, not the ingestion of fresh milk, was the main contributor to thyroid dose for exposure to 131I (even though dietary intake of vegetables was less in the past than at present), and b. the probability distribution assigned to the fraction of iodine released in the elemental form (Uniform 0, 0.6) is responsible for 64.6% of the total uncertainty in thyroid dose, given a unit release of 131I to the atmosphere. The assumptions used in the paper by Simpkins and Hamby leadmore » to a large overestimate of the contamination of vegetables by airborne 131I. The interception by leafy and non-leafy vegetables of freshly deposited 131I is known to be highly dependent on the growth form of the crop and the standing crop biomass of leafy material. Unrealistic assumptions are made for losses of 131I from food processing, preparation, and storage prior to human consumption. These assumptions tend to bias their conclusions toward an overestimate of the amount of 131I retained by vegetation prior to consumption. For example, the generic assumption of a 6-d hold-up time is used for the loss from radioactive decay for the time period from harvest to human consumption of fruits, vegetables, and grains. We anticipate hold-up times of many weeks, if not months, between harvest and consumption for most grains and non-leafy forms of vegetation. The combined assumptions made by Simpkins and Hamby about the fraction of fresh deposition intercepted by vegetation, and the rather short hold-up time for most vegetables consumed, probably caused the authors to conclude that the consumption of 131I-contaminated vegetables was more important to dose than was the consumption of fresh sources of milk. This conclusion is surprising, given that the consumption rate assumed for whole milk was rather large and that the value of the milk transfer coefficient was also higher and more uncertain than most distributions reported in the literature. In our experience, the parameters contributing most to the uncertainty in dose for the 131I air-deposition-vegetation-milk-human-thyroid pathway are the deposition velocity for elemental iodine, the mass interception factor for pasture vegetation, the milk transfer coefficient, and the thyroid dose conversion factor. In none of our previous investigations has the consumption of fruits, vegetables, and grains been the dominant contributor to the thyroid dose (or the uncertainty in dose) when the individual also was engaged in the consumption of even moderate quantities of fresh milk. The results of the relative contribution of uncertain input parameters to the overall uncertainty in exposure are counterintuitive. We suspect that calculational errors may have occurred in their application of the software that was used to estimate the relative sensitivity for each uncertain input variable. Their claim that the milk transfer coefficient contributed only 4% to the total uncertainty in the aggregated transfer from release to dose, and that the uncertainty in the vegetation interception fraction contributed only 3.3%, despite relatively large uncertainties assigned to both of these variables, violates our sense of face validity.« less

TRANSFER OF 131I INTO HUMAN BREAST MILK AND TRANSFER COEFFICIENTS FOR RADIOLOGICAL DOSE ASSESSMENTS

Data on transfer of radioiodine into human milk are rare in the literature. Data from sixteen publications were reviewed and analyzed to estimate the transfer coefficient (f(hm)*, having units of d L(-1)). The data on the radioiodine concentration in breast milk were analyzed by two methods: direct numerical integration and integration of a fitted exponential model. In general, the integrated fitted functions were greater. The fitted functions likely better describe the transfer into milk since few data sets sampled mothers' milk near the time of maximum excretion. The derived transfer coefficient values seem to represent two populations. The first group was those individuals who had very low excretions, including those where thyroid and mammary uptake was impaired by the administration of stable iodine or iodinated compounds. The second group included those with much higher excretions. The second group, termed the "normal-excretion" group, had transfers of iodine to milk that were more than ten-fold higher than in the "low-excretion" group. The derived milk transfer coefficient data for the low- and normal-excretion groups fitted to lognormal distributions gave geometric means, (geometric standard deviations), of 0.043 d L(-1) (2.1, n = 14) and 0.37 d L(-1) (1.5, n = 12), respectively. Estimates of the effective half-time (time from maximum concentration to half the value) were determined for the low- and normal-excretion groups separately. There was evidence that the effective half-time was longer for the normal- than for the low-excretion group; the geometric mean (and geometric standard deviation) were 12 (1.7) and 8.5 (2.6) h, respectively, though the difference was not statistically significant. The geometric mean times to maximum milk concentration in the low- and normal-excretion groups were nearly identical, 9.4 (3.1) and 9.0 (1.6) h, respectively. The data show that administration of large doses of stable iodine (commonly used to block uptake of iodine into the thyroid) is also an effective means to block radioiodine transfer into milk. Thus, protecting the mother's thyroid also protects the nursing infant. Despite inadequacies of available data describing the transfer of radioiodine to human milk within a healthy population of women, the values of f(hm)* provided here are believed to be the best available for use in radiological assessments. These values are particularly applicable to lactating women having normal diets and availability to stable iodine, as in the United States.

Influence of stable iodine on the transfer of 131I into cows' milk.

The effect of supplying three different stable iodine levels (about 70, 80, and 160 mg day-1) in the daily feed of four dairy cows has been studied for the excretion pattern of 131I. None of the different treatments had a statistically significant effect. A mean milk transfer coefficient of 0.015 +/- 0.001 d l-1 was determined for all iodine supply levels investigated.

The transfer of 137Cs and 90Sr along the soil-pasture-cows' milk pathway in an area of land reclaimed from the sea

An area of reclaimed land on the Lancashire coast of the UK has been used to provide data on transfer parameters in the soil-pasture-milk foodchain pathway when the activity is almost entirely of marine origin. Measured grass: soil concentration ratios for 137Cs were at the lower end of the range of values published by the International Union of Radioecologists (IUR), and about five times lower than the figure recommended by them for generic assessments. Feed: milk transfer coefficients for 137Cs between June and September 1988 were about half of the value considered appropriate when all of the ingested activity was in an available form. This can be accounted for by the ingestion of soil during open-pasture grazing, together with the observation that most of the soil-associated radiocaesium would be relatively unavailable for uptake. For 90Sr, the grass: soil concentration ratios were one to two orders of magnitude higher than those for 137Cs and close to the generic soil: grass transfer factor recommended by the IUR. The ingestion of soil-associated activity was not an important contributor to intake for this radionuclide. Moreover, a significant fraction of the soil-associated activity was found to be soluble in rumen fluid. The results of this work are discussed in terms of their applicability to other situations involving the introduction of radionuclide-bearing marine sediment into the terrestrial environment.

Transport of 131I and 137Cs from air to cows' milk produced in North-Western Italian farms following the Chernobyl accident

After the Chernobyl accident, the levels of 131I and 137Cs were measured in surface air, pasture grass and milk produced by cows fed exclusively on fresh grass. The observed values of the vegetation-to-air, milk-to-vegetation and milk-to-air concentration ratios were compared with the values predicted by an internationally recognized assessment model for the transfer of radionuclides through terrestrial food chains. Predicted values were higher than the observed results by factors of 2·6, 2·1 and 5·6 for 131I and 4·3, 3·7 and 16 for 137Cs, for the vegetation-to-air, milk-to-vegetation and milk-to-air ratios, respectively. A better agreement between prediction and observation was achieved by using experimental values of the following parameters; the mass interception factor ( R/Y), the effective decay constants on vegetation ( λ v ) and the milk transfer coefficients ( F m ), these being lower than the model default values. Milk produced by dairy cows fed on a mixed diet showed a different behaviour with regard to excretion of 137Cs.

Radiocaesium transfer to Ewes Fed contaminated hay after the chernobyl accident: Effect of vermiculite and AFCF (Ammonium Ferricyanoferrate) as countermeasures

Contaminated hay harvested in the south-east of France in June 1986 was fed to lactating and non-lactating ewes for 50–60 days. The mean transfer coefficients observed were 0·075 days litre −1 ( SD = 0·004) to milk ( n = 3) and 0·11 days kg −1 ( SD = 0·01) to meat ( n = 5). Adding vermiculite to feed pellets decreased the transfer coefficients by a factor of 2·5 to both milk and meat if given at 30 g day −1; a factor of 8 difference was reached using 60 g day −1 added vermiculite or 2 g day −1 ammonium ferricyanoferrate (AFCF). No adverse effects on intake rates, animal weight or milk production were observed during the administration period (90–100 days, 50–60 days during the oral contamination and 40 days during the depletion period), whatever the treatment. Three lactating goats were fed the same contaminated hay, but chopped and mixed with powdered maize, for 15 days. The mean milk transfer coefficient was lower than that for ewes at 0·032 days litre −1 ( SD = 0·05).

Experimental determination of transfer coefficients of 137Cs and 131I from fodder into milk of cows and sheep after the Chernobyl accident.

Following the Chernobyl accident in April 1986, the transfer of 131I and 137Cs from feed to milk was studied under experimental and common agricultural conditions. From measurements in different dairy farms in Southern Bavaria, equilibrium transfer coefficients for cow's milk were calculated to be 0.003 d L-1 (range 0.0015 to 0.005) for 131I and 0.003 d L-1 (range 0.0025 to 0.004) for 137Cs. In feeding experiments with cows and sheep under more controlled conditions, milk transfer coefficients of 0.007 d L-1 (range 0.0055 to 0.0081) for 131I and 0.003 d L-1 (range 0.0023 to 0.0053) for 137Cs were obtained for cows, while for sheep the 137Cs transfer coefficient was higher: 0.06 d L-1. The kinetics of the Cs transfer from fodder to cow's milk can be described by two exponential terms assuming biological half-lives in milk of 1-2 d and 10-20 d. The use of a fast component with 1.5 d and a fraction of 0.8, and a slow component with 15 d, gives a good approximation to the kinetics for all cows in this experiment.

Assessment of milk transfer coefficients for use in prediction models of radioactivity transport

The transfer coefficient (F m) which is widely used to predict the fraction of ingested radionuclides found in milk is an important parameter for modelling. The accuracy of estimates can be improved by considering the following factors that influence the F m; (1) the physical-chemical form of the radionuclide in the feed of cows, (2) the hay to concentrate ratio of cows diets and (3) correcting for a steady state situation for feed intake and milk concentrations. Factors such as stable element intake, soil intake, milk production rate, metabolic rate and inhalation do not appear to have significant effects upon the transfer coefficient.

Technetium Metabolism by Lactating Goats

The goat milk transfer coefficients of 99mTc, 95mTc and 99Tc, administered as pertechnetate (TcO4-), were 1.5 x 10(-4), 8.5 x 10(-4) and 1.1 x 10(-2) d L-1, respectively. The differences between the goat milk transfer coefficients of the three Tc isotopes administered as TcO4- were significant (p less than 0.05). The milk transfer coefficients of Tc were affected by chemical form and specific activity. Reduced 99mTc produced a transfer coefficient 17 times lower than that of 99TcO4- in the same goats. Reduction of pertechnetate in the rumen was evaluated to explain the low and variable transfer coefficients.

A specific activity effect in the metabolism of Tc.

A study of transfer to milk of three isotopes of Tc indicated different results for 99mTcO4-, 95mTcO4-, and 99TcO4-. When the three isotopes were given orally to lactating goats in separate experiments, the milk transfer coefficients increased with decreasing specific activity. Gut absorption of Tc administered as pertechnetate (TcO4-) was decreased by reduction of TcO4- in the rumen. The rate of reduction of TcO4- in the rumen was greater for higher specific activity doses of Tc. These results suggest that the specific activity of a radioisotope may significantly influence the estimated dose to humans from contaminated milk and, probably, other food products.

Transport of 131I through the grass-cow-milk pathway at a northeast US dairy following the chernobyl accident

Following the Chernobyl accident, samples of pasture grass and fresh farm milk were collected in northern New Jersey. The time-integrated activities of 131I were used to calculate a milk transfer coefficient of 0·001 d liter −1. This value is at the lower range of those previously reported. No significant difference in the value of the transfer coefficient was seen when calculated based on the integrated 131I in the total grass as compared to only the upper portion of the grass. Therefore, for this event, the height of the vegetation grazed by the cows would not have influenced the concentration of 131I in fresh milk.

Transfer of Fallout Strontium-90 to Cows’ Milk

From 1962 through 1966, the monthly 90Sr fallout rate, the accumulated deposit, and the concomitant 90Sr levels in animal forage and milk were measured in samples collected at the Colorado State University dairy farm in Fort Collins. During the growing period, 42% of the total 90Sr deposit was retained on alfalfa hay at the first cutting, 29% at the second cutting, and 23% at the third cutting. The difference between the first cutting and the two following was significant. These deposition coefficients combined with values for the area of forage utilized by the animal can be used to predict the contamination level of alfalfa hay from the measured total deposit.The total intake of 90Sr and the amount secreted in milk were measured in several groups of dairy cows. The transfer coefficients of 90Sr from diet to milk ranged from 0.05–0.09% per liter of milk per day and were in agreement with tracer and field experiments reported by other investigators. By using the appropriate deposition coefficient, forage yield, forage intake, and diet to milk transfer coefficient, the amount of 90Sr in milk was calculated from the measured total 90Sr deposit over the growing period. The calculated 90Sr in milk levels agreed reasonably well with measured values. For example, during the 1963 growing season—a period of relatively high fallout rate–the calculated amount of 90Sr in milk was 18 pCi per liter based on a measured deposit of 2.66 nCi 90Sr per m2 Milk samples collected during the same period and analyzed for 90Sr showed 20 pCi per liter.