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Previous work has indicated that radiation doses from deposition on human skin, hair and clothing may contribute significantly to the dose received after a major nuclear accident, such as that, which happened at Chernobyl in 1986. The available data was,however, sparse and associated with considerable variation, clearly showing a need for further investigations to verify preliminary conclusions, examine processes in greater detail and identify important factors causing the observed parameter variation.For instance, the impacts of thermophoresis, electrophoresis, skin moisture and wind speed on the deposition of contaminant aerosol were examined, and since the previous measurements had indicated that elemental iodine could be a particularly problematiccontaminant, experimental work was additionally undertaken to examine the process of deposition of this species to skin. Since both clearance and percutaneous penetration of deposited contaminants could play important roles in determining doses,experimental programmes were dedicated to the identification of parameters of interest in these contexts. Also doses from contamination on different surfaces in the indoor environment have in the past traditionally been neglected, and a theoreticalapproach, based on measurements, was developed for accurate prediction of these doses under different conditions. Also resuspension of deposited matter and its role in dose formation, by subsequent deposition or inhalation, was investigated throughexperiments. Contact transfer of contaminants from an indoor surface to human skin may give yet another contribution to dose and also the relevant parameters in this direction were examined experimentally. The ultimate goal of the investigations was toenable the determination of the various contributions to dose in a contaminated indoor environment. A model methodology was developed and an example of its use was given. It was found that after a major nuclear accident, doses from indoor deposition tohumans, deposition on indoor surfaces and inhalation in the indoor environment would all be important to consider. Previous work has indicated that radiation doses from deposition on human skin, hair and clothing may contribute significantly to the dose received after a major nuclear accident, such as that, which happened at Chernobyl in 1986. The available data was, however, sparse and associated with considerable variation, clearly showing a need for further investigations to verify preliminary conclusions, examine processes in greater detail and identify important factors causing the observed parameter variation. For instance, the impacts of thermophoresis, electrophoresis, skin moisture and wind speed on the deposition of contaminant aerosol were examined, and since the previous measurements had indicated that elemental iodine could be a particularly problematic contaminant, experimental work was additionally undertaken to examine the process of deposition of this species to skin. Since both clearance and percutaneous penetration of deposited contaminants could play important roles in determining doses, experimental programmes were dedicated to the identification of parameters of interest in these contexts. Also doses from contamination on different surfaces in the indoor environment have in the past traditionally been neglected, and a theoretical approach, based on measurements, was developed for accurate prediction of these doses under different conditions. Also resuspension of deposited matter and its role in dose formation, by subsequent deposition or inhalation, was investigated through experiments. Contact transfer of contaminants from an indoor surface to human skin may give yet another contribution to dose and also the relevant parameters in this direction were examined experimentally. The ultimate goal of the investigations was to enable the determination of the various contributions to dose in a contaminated indoor environment. A model methodology was developed and an example of its use was given. It was found that after a major nuclear accident, doses from indoor deposition to humans, deposition on indoor surfaces and inhalation in the indoor environment would all be important to consider.

In the past, very little thought has been given to the processes and implications of deposition of potentially hazardous aerosol directly onto humans. This state of unpreparedness is unsatisfactory and suitable protocols have been developed and validatedfor tracer experiments to investigate the deposition and subsequent fate of contaminant aerosol on skin, hair and clothing. The main technique applied involves the release and subsequent deposition on volunteers in test rooms of particles of differentsizes labelled with neutron activatable rare earth tracers. Experiments indicate that the deposition velocity to skin increases linearly with the particle size. A wind tunnel experiment simulating outdoor conditions showed a dependence on skin depositionvelocity of wind speed, indicating that outdoor deposition velocities may be great. Both in vivo and in vitro experiments were conducted, and the influence of various factors, such as surface type, air flow, heating and electrostatics were examined. Thedynamics of particle removal from human skin were studied by fluorescence scanning. This technique was also applied to estimate the fraction of aerosol dust transferred to skin by contact with a contaminated surface. The various parameters determined wereapplied to establish a model for calculation of radiation doses received from deposition of airborne radioactive aerosol on human body surfaces. It was found that the gamma doses from deposition on skin may be expected to be of the same order of magnitudeas the gamma doses received over the first year from contamination on outdoor surfaces. According to the calculations, beta doses from skin deposition to individuals in areas of Russia, where dry deposition of Chernobyl fallout led to very high levels ofcontamination, may have amounted to several Sievert and may thus be responsible for a significant cancer risk. In the past, very little thought has been given to the processes and implications of deposition of potentially hazardous aerosol directly onto humans. This state of unpreparedness is unsatisfactory and suitable protocols have been developed and validated for tracer experiments to investigate the deposition and subsequent fate of contaminant aerosol on skin, hair and clothing. The main technique applied involves the release and subsequent deposition on volunteers in test rooms of particles of different sizes labelled with neutron activatable rare earth tracers. Experiments indicate that the deposition velocity to skin increases linearly with the particle size. A wind tunnel experiment simulating outdoor conditions showed a dependence on skin deposition velocity of wind speed, indicating that outdoor deposition velocities may be great. Both in vivo and in vitro experiments were conducted, and the influence of various factors, such as surface type, air flow, heating and electrostatics were examined. The dynamics of particle removal from human skin were studied by fluorescence scanning. This technique was also applied to estimate the fraction of aerosol dust transferred to skin by contact with a contaminated surface. The various parameters determined were applied to establish a model for calculation of radiation doses received from deposition of airborne radioactive aerosol on human body surfaces. It was found that the gamma doses from deposition on skin may be expected to be of the same order of magnitude as the gamma doses received over the first year from contamination on outdoor surfaces. According to the calculations, beta doses from skin deposition to individuals in areas of Russia, where dry deposition of Chernobyl fallout led to very high levels of contamination, may have amounted to several Sievert and may thus be responsible for a significant cancer risk.

The deposition to human body surfaces of potentially hazardous aerosol has been investigated through tracer experiments. Particles of different sizes labelled with neutron activatable rare earth tracers were released in test rooms and deposited on volunteers. Various sampling techniques to examine the clearance and retention of the aerosol to skin, hair and clothing were investigated, and a protocol for the most efficient procedure was established and validated. Experiments indicate that the deposition velocity to skin increases linearly with the particle size. A wind tunnel experiment simulating outdoor conditions showed outdoor deposition velocities to be almost an order of magnitude higher than those recorded indoors. Both in vivo and in vitro experiments were conducted, and the influence of various factors, such as surface type, air flow, heating and electrostatics were examined. The dynamics of particle removal from human skin were studied by fluorescence scanning. Using the experimentally determined parameters, a model was established for calculation of radiation doses received from deposition of airborne radioactive aerosol on human body surfaces. It was found that the gamma doses that could be expected from deposition on skin were of the same order of magnitude as the gamma doses received over several years from contamination on outdoor surfaces. Assuming very high dry contamination levels, as were recorded in some areas of Russia after the Chernobyl accident, it was found that beta doses from skin deposition may amount to several Sievert and thus be responsible for a significant cancer risk.