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Question:
Is dividing beta emissions into two categories: low energy (< 10keV) and high energy (> 10 keV) an adequate simplification or does this introduce significant uncertainty for beta energy that is degrading as it enters the biota, losing energy in the process?
Answer:
The low beta component is calculated separately because a higher relative biological effectiveness (RBE) has been observed for tritium (see references). It is prudent to assume that the experimental RBEs for tritium reflect the elevated LET values for low energy beta particles and electrons, and thus we recommend application of a weighting factor of 3, greater than unity to all such beta particles and electrons, regardless of the radionuclide from which they originate. For high-energy betas and electrons the weighting factor is 1, indicating same RBE than the reference radiation (gamma).

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