Abstract
The quality and quantity of data used to derive transfer parameter values for milk are variable and there are many data gaps for elements/radionuclides which may need to be considered for risk assessment of the agricultural foodchain. There has been a recent focus on critically evaluating current methods to fill data gaps and on identifying extrapolation methods to derive suitable values for the elements, and particularly radioisotopes, with no or sparse data. The relationship between fractional absorption of elements in the ruminant gastrointestinal tract and transfer to milk has been explored to determine whether knowledge of the former can be used to predict the latter. A relationship has been derived between fractional absorption of elements and two empirical ratios commonly used to quantify transfer to milk; transfer coefficients (element concentration in milk divided by element daily intake) and concentrations ratios (concentration in milk divided by concentration in feed). We propose that fractional absorption may be used to predict the order of magnitude of the transfer to milk of elements/radionuclides for which no relevant data have yet been identified or collated.
Highlights
The quality and quantity of data used to derive transfer parameter values for milk are variable and there are many data gaps for elements/radionuclides which may need to be considered for risk assessment of the agricultural foodchain
The method used to define the data for the ruminant absorption values differed from that of the ICRP18 for the human alimentary tract model where fractional absorption values (Fa) values were based on expert review of literature
The Fa values for ruminants (Table 1) are generally within an order of magnitude of those reported by ICRP, with some exceptions
Summary
The quality and quantity of data used to derive transfer parameter values for milk are variable and there are many data gaps for elements/radionuclides which may need to be considered for risk assessment of the agricultural foodchain. The use of concentration ratios (CR) has been suggested, which removes the need to quantify the total intake of the animal as it uses the concentration in the feed (Bq kg−1 dry weight (dw)) as the denominator rather than the intake[1,2] Both these authors suggested that there is a potential advantage of the use of CR values in that they are less variable than transfer coefficients and easier to obtain. There are significant disadvantages in the use of such approaches including a lack of rigour, provenance, quality control or peer review[15]
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