Operational Values of Radioactive Skin Contamination in the Case of Radiological Accident

Abstract

Purpose: Development of recommendations on the use in medical practice of institutions under FMBA of Russia of operational values of radioactive skin contamination in the event of radiological accidents.
 Material and methods: The easily measured radiation parameters were used as operational values: ambient dose equivalent rate (ADER) of γ-radiation, density of skin contamination with γ-, β- and α-emitting radionuclides. Operational values ​​of skin contamination were estimated on the basis of experimental data described in the literature and models on the kinetics of radioactive substances transport in the body, accepted values ​​of dose criteria for deterministic and stochastic effects. The estimation of radioactive material resorption through the skin was based on the results of experimental studies in laboratory animals (mainly piglets) for a limited set of chemical compounds of radionuclides.
 Results: The values of γ-ADER of the main dose-forming radionuclides measured at a distance of 10 cm from the skin surface in the range of 10–1000 μSv/h and the possible health effects due to the skin exposure and the intake of radioactive substances into the body were presented. In the IAEA recommendations, the level of skin contamination at 1 µSv/h is considered as a significant operational value according to the criterion of radioactive substances intake through the mouth from the contaminated surface of the hands. However, in our opinion, this estimate is excessively conservative; therefore it is not included in the recommended operational values. If the skin is contaminated with γ-β-emitting radionuclide solutions at a surface contamination higher than 106 Bq/cm2 (ADER ≥1000 µSv/h), the out of turn emergency decontamination should be carried out. Obligatory indications for the whole body counter examination after thorough decontamination and conducting biophysical analysis of bioassay are the following operational values: γ-ADER from the skin > 10 µSv/h; surface contamination of intact skin with β-active radionuclides > 20 000 β-part./(cm2·min); surface contamination of intact skin with α-active radionuclides > 200 α-part./ (cm2·min).
 Conclusion: The recommended operational values allow preliminarily and promptly to assess the health risk not only in the case of external (contact) exposure of the skin and underlying tissues, but also due to the intake of soluble radioactive substances into the body through intact and damaged (injured) skin. Taking into account the high degree of uncertainty of the estimates obtained, the operational values ​​should be considered as strictly conservative. They should be used only to determinate of urgency of decontamination carrying out for the provision of medical care during the prehospital and early hospital periods with the obligatory follow-up dosimetry examination for the final assessment of absorbed dose.