Allometric methodology for the assessment of radon exposures to terrestrial wildlife

A practical approach to calculate 222Rn daughter dose rates to terrestrial wildlife is presented. The method scales allometrically the relevant parameters for respiration in different species of wildlife, allowing interspecies calculation of the dose per unit radon concentration in air as simple base-and-exponent power functions of the mass. For plants, passive gas exchange through the leaf surface is assumed, also leading to specific power relationships with mass. The model generates conservative predictions in which the main contributor to the dose rate of target tissues of the respiratory system is from α radiation arising from 222Rn daughters. Tabulated 222Rn DPURn values are given for 69 species used by the England & Wales Environment Agency for habitats assessments. The approach is then applied to assess the authorised discharges of 222Rn from sites in England, demonstrating that, from a whole-body dose perspective, the biota considered are protected from effects at the population level.