Abstract
The eye lens exposure among 16 technicians in two nuclear medicine departments at university hospitals in Finland was investigated by measuring the operational quantity Hp(3) using EYE-D dosemeters. For all workers, the annual mean Hp(3) was estimated to be 1.1 mSv (max. 3.9 mSv). The relation between Hp(3) to routinely monitored personal dose equivalent Hp(10) was clearly correlated. Considering individual dose measurement periods (2–4 weeks), the Hp(3)/Hp(10) ratio was 0.7 (Pearson’s coefficient r = 0.90, p < 0.001, variation of ratio 0.1–2.3). The variation decreased considerably with increasing Hp(10) (σ2 = 0.04 vs. 0.43 for Hp(10) > 0.1 mSv vs. < 0.1 mSv, respectively), i.e. higher Hp(10) predicts Hp(3) more reliably. Moreover, annual Hp(10) data from national dose register during 2009–2018 were used to derive the annual Hp(3) applying the Hp(3)/Hp(10) ratio. The data from Finnish nuclear medicine departments imply that routine measurements of Hp(3) among nuclear medicine technicians are not justified.
Highlights
The allowed annual equivalent dose to the lens of the eye for occupational exposure has been prominently reduced from 150 mSv to a mean value of 20 mSv obtained over a period of 5 years and with no single year exceeding 50 mSv
A large number of other investigations, the International Commission on Radiological Protection (ICRP) concluded that the lifetime dose threshold for induction of cataracts needs to be lowered to an absorbed dose of 0.5 Gy by acute or protracted exposure(5)
The ICRP 2012 states that ‘the new recommended equivalent dose limit for occupational exposure of the lens of the eye is based on prevention of radiogenic cataracts’
Summary
The allowed annual equivalent dose to the lens of the eye for occupational exposure has been prominently reduced from 150 mSv to a mean value of 20 mSv obtained over a period of 5 years and with no single year exceeding 50 mSv. A large number of other investigations, the International Commission on Radiological Protection (ICRP) concluded that the lifetime dose threshold for induction of cataracts needs to be lowered to an absorbed dose of 0.5 Gy by acute or protracted exposure(5). The ICRP 2012 states that ‘the new recommended equivalent dose limit for occupational exposure of the lens of the eye is based on prevention of radiogenic cataracts’. Many states, Finland included, have implemented the equivalent dose limits for the lens of the eye from the new basic safety standards into national legislation (Finnish Radiation Act 859/2018, 2018, Finnish Government Decree on Ionising Radiation 1034/2018, 2018). In the case of the lens of the eye, Hp(3) (i.e. personal dose equivalent to the lens of the eye) can be used to estimate the protection quantity equivalent dose to the lens of the eye
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