ICRP Statement on Radon AND Lung cancer risk from radon and progeny

Draft document: ICRP Statement on Radon AND Lung cancer risk from radon and progeny
Submitted by Frank Harris, BHP Billiton
Commenting on behalf of the organisation

Preamble BHP Billiton is the world's largest diversified natural resources company. We are distinguished from other resource companies by the combination of the quality of our assets; our deep inventory of growth projects; our customer-focussed marketing; our diversification across countries, commodities, and markets; and our petroleum business. As at 30 June, 2009 we had some 40,990 employees working in over 100 operations in 25 countries. Reflecting our aim to be a premier global company, we occupy significant positions in major commodity businesses, including aluminium, energy coal and metallurgical coal, copper, manganese, iron ore, uranium, nickel, silver and titanium minerals, and have substantial interests in oil, gas, liquefied natural gas and diamonds. In uranium we are the full owner of the Olympic Dam deposit and producing underground mine and process plant in South Australia and are also the full owner of the Yeelirrie deposit in Western Australia. We currently have approximately 3500 workers at Olympic Dam of which approximately 1000 are designated radiation workers. The exposure to radon and radon decay products is of importance to our underground workforce and we are committed to ensuring the best possible radiation protection systems are used to ensure their ongoing health and safety. General Response BHP Billiton welcomes the opportunity to comment on the draft ICRP publication on Lung Cancer Risk from Radon and Progeny. The practical and appropriate implementation of radiation protection is critical to the nuclear industry and particularly in the mining and processing of uranium. As such any change in the dosimetry or underlying risk is of high importance. Publication Comments The publication provides a comprehensive review of the ongoing epidemiology studies of radon, both at home and at work. The draft report builds upon the latest UNSCEAR report on radon (UNSCEAR 2009) and comes to similar conclusions on the numerical risks of radon from combined residential studies and combined miner studies. Both these reports highlight the appropriateness of the existing system for protection from radon with the risk directly based on the epidemiological findings. BHP Billiton fully supports the ongoing refinement of the epidemiological studies as more information becomes available and the results forming the basis for systems of protection. In particular the increase in the nominal risk coefficient by 75% (from 8*10-5 to 14*10-5 mJhm-3) {lines 79-81} is significant and we await further details on how this will be practically implemented into the radiation protection system. However, there remains considerable uncertainty about the proposed shift to a system based on dosimetric and biokinetic modelling. Just because the dosimetric approach appears to be close to the epidemiological data is not a key driver for its adoption over the epidemiological approach. Because of the apparent epidemiological evidence of risk from radon it would seem logical to utilise this as the basis for protection. It also is an approach which is publically transparent and similar to that used for other carcinogens which have direct epidemiological evidence. There are many key aspects of the behaviour of radon decay products (RDP) which are different to conventional application of biokinetic and dosimetric models such as that currently used for inhalation and ingestion of other radionuclides. In particular, the potential prevalence and impact of ultra fine particles (<0.1 um) is poorly defined and understood. It would be recommended that more information on the nature of the underlying factors was researched prior to the implementation of a dosimetric approach. Within the publication there are aspects which highlight the concern about how the dosimetric approach will be implemented. Although the report quotes a change of risk factor of approximately 75%, the potential change in dose conversion factor for standard workers mentioned in Apendix B was >400% (a change from 1.4 mSv per mJhm-3 to 6 mSv per nJhm-3) {lines 211, 1444-1446}. This difference is not explained sufficiently and could have significant impacts on uranium and non-uranium operations. This potential large increase in dose conversion does not seem to be reflected in either the overall or miner based epidemiology. It also raises potential concerns that practices in place to reduce other potential hazards, such as diesel particulates and reduced residency times, may give rise to higher calculated doses (due to reduction in particle size). There is also very limited knowledge of the characteristics of RDP in home, environmental or occupation situations and this will restrict the ability to determine the consequences of application of dosimetric and biokinetic models. Given the lack of research into RDP particle sizing over the last two decades, collection of this base data should be a predecessor for the adoption of the dosimetric approach. This information is critical for aligning the dosimetric approach with the epidemiological evidence to ensure the two approaches are aligned. BHP Billiton, with Rio Tinto, Areva and Cameco, are developing programs to investigate these aspects and add to the base knowledge of the biokinetic parameters of RDP. Although epidemiological aspects of the smoking cofounder are included in the report {Lines 627-635}, there is also no indication if there will be any inclusion of this parameter in future dosimetric considerations. This could potentially impact on the protection requirements for this group of occupational or potentially publically exposed individuals (for the case of rehabilitation of current practices such as minesite remediation). There also appears to be some differentiation of the epidemiology, with respect to the smoking cofounder, between the mining and home studies. It is hoped that further epidemiological work will address this and provide further definition on the extent and implications of the cofounder. It was noted in the report the continued use of the non-SI unit the WL and mSv per WLM and the use of the mSv per mJhm-3. As this unit includes the use of breathing rate in its definition it is questioned whether a better SI unit of mSv per mJ would be a better reflection of dose coefficient. This is far more consistent with other non RDP dose conversions (ie mSv per Bq) and also removes some of the variation in dose conversion between public and occupational exposure. It would also simplify the application of the dose conversion to areas where non-standard breathing rates are in use or different standard man models are used. It is also easier to explain to the workforce and the public where you can step through the calculation of how much is inhaled and then to dose. BHP Billiton supports the efforts of the ICRP to provide the best possible system of radiation protection. BHP Billiton looks forward to further details and consultation on the radiation protection aspects of radon and RDP. BHP Billiton would also be willing to assist the ICRP on any additional data requirements they may have in this area and also in the provision of advice on the practical application and implications of the forthcoming changes.