On several occasions in recent years uranium mining companies have brought guest speakers to Australia to argue that low-level radiation exposure is not only harmless but actually good for you. To promote such marginal views without any counter-balance is self-serving and irresponsible and it may be time for governments to step in to provide that balance.
Recent research has heightened rather than lessened concern about the adverse health impacts of low-level radiation. Moreover the latest science - concerning the health impacts of exposure to radon gas - is important in the context of the ongoing debate over uranium mining in Australia.
In 2009, the International Commission on Radiological Protection (ICRP) stated that radon gas delivers twice the radiation dose to humans as originally thought and is in the process of reassessing permissible levels. At this stage, previous dose estimates to miners need to be approximately doubled to accurately reflect the lung cancer hazard.
At BHP Billiton's Olympic Dam underground uranium/copper mine in South Australia, the total dose per miner is approximately 6 millisieverts (mSv) per year allowing for the new ICRP dose coefficients). These doses are typical of modern mine practices.
The average miner at Olympic Dam is young (and at greater risk of developing lung cancer than older workers) and stays on average five years at the site. A typical calculation using the latest figures of radiation carcinogenesis risks indicates that the average miner has a 1:670 chance of contracting cancer, most likely lung cancer, as a result of workplace radiation exposure.
Most modern uranium mines have air extraction systems and radon levels are monitored. Miners are given protective equipment including masks to filter out radioactive particles. However, many underground miners find the masks extremely uncomfortable, especially in the hot underground environment they must contend with. It is estimated that around 50 per cent of underground uranium miners in Australia do not use their masks and are thus at greater risk of lung cancer. It is debatable whether miners are informed of these risks in a full and accurate manner so that they can make informed work decisions.
The industry peak body, the Australian Uranium Association (AUA), has a responsibility to act. AUA members include companies such as Toro Energy, Uranium One and Heathgate Resources that have been promoting the view that low-level radiation is beneficial, and funding the Australian visits of people prepared to promote those views.
Yet the AUA has made no apparent effort to counter those marginal views with the conventional scientific understanding that there is no threshold below which radiation is harmless let alone beneficial. And the AUA itself sends mixed messages. For example its website asserts that there is insufficient evidence to overturn the no-threshold model but also states that there is "no evidence" of harmful health effects of annual exposures of 1.5-3.5 mSv.
In fact there is evidence of harmful effects from low-level radiation exposure. For example, the 1999 Biological Effects of Ionising Radiation VI report reviewed 11 studies covering 60,000 underground uranium miners. The report found an increasing frequency of lung cancer in miners, proportional to the cumulative amount of radon exposure. A 15-country study of nuclear industry workers (excluding mining) published in 2005, the largest study of nuclear industry workers ever conducted, found a statistically-significant increased risk of cancer and leukaemia in nuclear industry workers, even at low radiation doses.
The Committee on the Biological Effects of Ionising Radiation, convened by the US National Academy of Sciences, noted in a comprehensive 2006 review of the evidence that "… there is a linear dose-response relationship between exposure to ionising radiation and the development of solid cancers in humans. It is unlikely that there is a threshold below which cancers are not induced."
If the mining companies and the AUA do not improve their act in short order, federal and state governments ought to invest in an educational campaign to ensure that the self-serving, marginal views promoted by parts of the industry are not mistaken for rigorous science. My profession - the medical profession - also has an important role to play.
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