Rio Tinto is a large multinational mining and processing company producing a range of resources throughout the globe. Rio Tinto, as part of its portfolio, is a major shareholder and operates two uranium mines (Rossing in Namibia and Ranger in Australia) and also has a range uranium exploration activities. Rio Tinto welcomes the opportunity to comment on the ICRP Draft Report on Occupational Intakes of Radionuclides Part 3.
This submission concentrates on the radon subsection of the draft report. Where possible the comments include the line reference to facilitate interpretation of the comments.
Paragraph 619 Lines 8281-8295 and elsewhere in report: The use of SI units is (ie, ”J”, “mSv/J”, “Jm-3”) should be the preferred mechanism for report by the ICRP. The units of” J h m-3” is not a “real” SI unit because the time and volume unit effectively incorporates a breathing factor and are not part of the true unit of exposure Joules (J). This does cause problems where different breathing rates are used (such as risk during different occupational activities). A more correct use of SI units would be to express the risk as a factor of “J” which removes the need for the breathing factor and is the base SI unit. This also leads to future references of effective dose per unit exposure (Para 713, lines 9288-9297; 719 lines 9353-9370) where dose conversion factors can be true SI units (ie “mSv/J” or “mSvJ-1”). It also would be far more consistent with other ICRP dose conversion factors (ie “mSv/Bq”).
Table 12-15 Lines 9363-9370: The data provided in the report highlighted both the scarcity of data and the variability of the existing data for radon progeny characteristics with occupational environments. As such the provision of two values to characterise the dose conversions for the range of atmospheres which will be encountered may be problematic. Given this uncertainty in the underlying assumptions, it may be premature to provide definitive values given the potential range of exposure situations. This also relates to the question of the most appropriate approach to the determination of radon progeny dose as it is one of the few areas of occupational exposure where there is good epidemiological data on which to base the risk assessment. Until sufficient data is available to quantify the atmospheric parameters and to provide calibration against the epidemiological evidence, it would be recommended that the ICRP continues to use dose conversion factors based on the epidemiological approach (corrected for the most recent studies).