Risks from Ionising and Non-Ionising Radiation
Risks from Ionising and Non-Ionising Radiation
Deputy Editor Maureen McQueen has over 30 years ' professional radiation protection experience in the UK, USA and Canada.
The risks of ionising radiation have been well studied for over a century. The current system of radiological protection( ICRP Publication 103) has been in place since 2007 and is adopted as the basis of radiation protection regulations in Europe and much of the world apart from North America.
Risk data are informed by extensive scientific research including a life span study on survivors of the Hiroshima and Nagasaki atomic bombs. These indicate an excess in the number of cancers resulting in death compared with the average population at high radiation doses.
Since the cancers induced by radiation occur following a latency period and are not distinguishable from those occurring from other causes, drawing conclusions from epidemiological studies to confirm the risks of radiation at low radiation exposures is complicated. The system of radiological
To learn about the differences between ionising and non-ionising radiation, see our Back to Basics pull-out on p. 40.
protection adopts a conservative approach based on the Linear Non-Threshold( LNT) model, which extrapolates data on the incidence of cancer at high radiation doses down to the doses typically found in occupational settings. This is based on the assumption that any level of radiation exposure results in a risk, i. e. there is no“ safe” exposure level. ICRP 103 estimates that for uniform radiation, the risk of developing a cancer is 0.055 per Sv for the whole population and 0.041 per Sv for adult workers. These risk coefficients apply to low doses at all dose rates, and to high doses at low dose rates.
Based on these risk coefficients, it is estimated that an average occupational dose of 20 mSv / year results in a risk of cancer of 0.08 %. This should be compared with the average lifetime risk of death from cancer, which in England is 27-28 %. Despite the comparatively low excess risk from ionising radiation, ICRP recommends that radiation exposures should additionally be kept As Low As Reasonably Achievable( ALARA), to account for an uncertainty in the risk modeling.
For non-uniform irradiation, the studies referenced in ICRP 103 have also been used to derive tissue weighting factors. These factors apply to the whole population, regardless of sex, and can be used to estimate doses and risks for non-uniform exposures where relevant.
As well as the cancer risk, which is the most relevant for day-to-day radiation exposures, ICRP 103 concluded that deterministic( i. e.
4 Radiation Protection Today www. srp-rpt. uk