Australian action to reduce health risks from radon

In Australia, worker exposure to radon in underground uranium mines has been a focus of policy makers and regulators, and has been well controlled in the industry sector. That cannot be said for public exposure to radon. Radon exposure studies in the late 1980s and early 1990s demonstrated that the levels of radon in Australian homes were some of the lowest in the world. The International Basic Safety Standards, published by the International Atomic Energy Agency, requires the government to establish and implement an action plan for controlling public exposure due to radon indoors. When considering different policy options, it is important to develop radon prevention and mitigation programmes reflecting elements that are unique to the region or country. The Australian Radon Action Plan is being considered at a national level, and presents a long-range strategy designed to reduce radon-induced lung cancer in Australia, as well as the individual risk for people living with high concentrations of radon. In Australia, workers who are not currently designated as occupationally exposed are also considered as members of the public. In the Australian context, there are only a limited set of scenarios that might give rise to sufficiently high radon concentrations that warrant mitigation. These include highly energy efficient buildings in areas of high radon potential, underground workplaces, workplaces with elevated radon concentrations (e.g. spas using natural spring waters), and enclosed workspaces with limited ventilation. The key elements for a successful plan will rely on collaboration between government sectors and other health promotion programmes, cooperative efforts involving technical and communication experts, and partnering with building professionals and other stakeholders involved in the implementation of radon prevention and mitigation.

Development of an energy discriminate CR-39(®) nuclear track etch dosimeter for Radon-220 gas measurements

An energy discriminate CR-39(®) nuclear track etch dosimeter for use in a (220)Rn and (222)Rn gas monitor has been developed and experimentally assessed. It utilises a thin film of Mylar(®) C to attenuate the alpha particle energies to allow only the damage tracks created by the 8.785 MeV alpha particles emitted from (212)Po of the (232)Th decay chain to be registered in the CR-39(®) plaque, allowing for the direct measurement of (220)Rn gas concentrations. The dosimeter was developed through a combination of experimental investigations and theoretical simulations using the Monte Carlo ion transport modelling program Stopping and Range of Ions in Materials (SRIM 2008). A film thickness of 54 μm has been shown to attenuate all alpha energies less then 7.7 MeV.

Method design and validation for the determination of uranium levels in human urine using high-resolution alpha spectrometry

Quantification of uranium in human urine is a valuable technique for assessing occupational and public exposure to uranium. A reliable method has been developed and validated in the ARPANSA Radiochemistry Laboratory by means of standard radiochemical separation and purification techniques and measurement using high-resolution alpha spectrometry. This method can be used to evaluate the levels of naturally occurring 234U, 235U and 238U in urine. Method design and validation is the process of defining an analytical requirement, and then confirming that the method under consideration has performance capabilities consistent with what the application requires. The method was designed to measure levels down to 2 mBq/day of total uranium, corresponding to approximately 1/100th of the annual committed effective dose of 20 mSv. Validation tests were developed to assess selectivity, accuracy, recovery and quantification of uncertainty. The radiochemical recovery of this method was measured using (232)U tracer. The typical minimum detectable concentration for total uranium for 24-h urine samples is approximately 0.6 mBq/day or 0.019 microg/day.

In vitro dissolution studies of uranium bearing material in simulated lung fluid

Inhaled uranium (U) bearing material will partially dissolve in the fluid lining of the lung, followed by a combination of retention, re-distribution, and excretion of the U. The rate of dissolution influences the retention time at the site of deposition, and the extent to which the material is available for re-distribution to other tissues. The consequential radiation dose is dependent upon the material distribution in the body and the exposure time to various tissues. The International Commission on Radiological Protection, ICRP 66 [International Commission on Radiological Protection (ICRP), 1994. Human Respiratory Tract Model for Radiological Protection. ICRP Publication 66] recommends the use of experimentally determined solubility coefficients in dose modelling. Material specific absorption parameters allow for better dose estimation than using ICRP default values for F (fast), M (moderate) and S (slow) classifications of U compounds. In vitro dissolution tests were carried out on U material collected from two U mines located in Australia. A static technique was designed in which particle samples were sandwiched between two 0.1-mum pore size membrane filters. The filter sandwich was exposed to a solvent (simulated lung fluid) for selected time intervals, at controlled test conditions for temperature and pH. The collected solution was analysed for U concentration using ICP-MS. The resulting dissolution curves were fitted with a double or triple exponential equation to determine the dissolution coefficients.