The Nuclear Energy Agency (NEA) invited policy makers, regulators, practitioners and researchers to participate in an online event to launch its newly issued report Regulatory Implementation of the Equivalent Dose Limit for the Lens of the Eye for Occupational Exposure: Successes and Challenges to the Approaches Identified Through a Survey of Regulators.

The report was produced by the NEA Expert Group on the Dose Limit for the Lens of the Eye (EGDLE), created in 2019 by the  Committee on Radiological Protection and Public Health (CRPPH), with the objective of providing an opportunity for regulators and stakeholders to share lessons learned in the practical implementation of the International Commission on Radiological Protection’s (ICRP’s) recommended equivalent dose limit for the lens of the eye for occupational exposures. It summarises the practical experiences of regulators and stakeholders worldwide in implementing the ICRP’s recommended equivalent dose limit for the lens of the eye for occupational exposure, including successes and challenges to the approaches.

• Ms Christina Dodkin, Chair of the NEA Expert Group on the Dose Limit for the Lens of the Eye (EGDLE), Radiological protection specialist, Canadian Nuclear Safety Commission
• With the assistance of the NEA technical secretariat, Mr Jan-Hendrik Kruse, Radiological Protection Specialist, and Dr Jacqueline Garnier-Laplace, Deputy Head, Division on Radiological Protection and Human Aspects of Nuclear Safety (RP-HANS)

• Dr Borislava Batandjieva-Metcalf, Secretary of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
• Prof Marie-Claire Cantone, Vice-Chair of the EGDLE, Chair of the International Radiation Protection Association (IRPA) Task Group on the Implementation of the Eye Lens Dose Limit, Professor of Applied Physics at the University of Milan, Italy
• Dr Marie-Anne Chevallier, member of the EGDLE, Chair of Working Group 2 on "Harmonisation of Individual Monitoring" of the European Radiation Dosimetry Group (EURADOS), researcher in dosimetry at the Institute of Radiological Protection and Nuclear Safety, France
• Dr Salah Djeffal, Canadian Nuclear Safety Commission's Lead Technical Advisor for Canada's Federal Nuclear Science and Technology research project on eye lens dosimetry, Chair of the Canadian Advisory Committee for ISO, Canada
• Dr Liz Ainsbury, Chair of EURADOS Working Group 10 on "Retrospective Dosimetry", member of ICRP Committee 1 on "Radiation Effects", Principal Radiation Protection Scientist, UK Health Security Agency
• Dr Thomas Otto, Representative from the International Commission on Radiation Units and Measurements (ICRU).
• Prof Werner Rühm, Chair of the International Commission on Radiological Protection (ICRP) and former chair of EURADOS

13:00 – 13:05 CET

Opening and welcome address

Mr William D. Magwood, IV, Director-General, Nuclear Energy Agency

13:05 – 13:30 CET

Overview of the report

Ms Christina Dodkin, Chair of the NEA Expert Group on the Dose Limit for the Lens of the Eye

• Main findings collected in a survey targeting national regulatory authorities;
• Identified areas of improvement and conclusions;
• Next steps to facilitate continued dialogue and information exchange.

Q&A session with the audience

13:30-14:50 CET

Panel discussion

• Theme 1: implementation aspects

(e.g., use of personal protective equipment, harmonisation of accreditation and technical specifications for Hp(3) eye lens dosimeters, improvement of the availability of eye lens dosimeters worldwide, use of surrogate dosimeters and correction factors, quality of related data in National Dose Registries, education and training)

Theme 1 will feature key highlights from Dr Djeffal, Dr Otto, Prof Cantone, and Dr Chevallier, followed by a Q&A session.

• Theme 2: research needs

(e.g., critical literature review, ongoing or planned research projects and their contribution to advancing aspects of radiological protection of the eye and/or improving eye lens dosimetry, insights on research that may impact our understanding of the effects of radiation exposure on the lens of the eye).

Theme 2 will feature key highlights from Dr Batandjieva-Metcalf, Prof Rühm, and Dr Ainsbury, followed by a Q&A session.

14:50-15:00 CET

Concluding remarks

Ms Christina Dodkin, Chair of the NEA Expert Group on the Dose Limit for the Lens of the Eye

Background - The Nuclear Energy Agency (NEA) report Regulatory Implementation of the Equivalent Dose Limit for the Lens of the Eye for Occupational Exposure: Successes and Challenges to the Approaches Identified Through a Survey of Regulators was highly awaited by regulators and  stakeholders from the nuclear, non-nuclear and medical communities worldwide, as evidenced by the large number of attendees to the virtual publication launch on 7 March 2022. Discussions focused on implementation aspects and research needs with subject-matter experts from relevant international organisations, professional associations, national regulatory bodies and research and expertise institutions. For continued dialogue in this area, a platform hosted by the NEA is being developed to exchange information on  advances in research related to eye dosimetry and effects of radiation exposure on the lens of the eye; advances in eye dosimetry related to technologies, accreditation, technical and performance specifications and intercomparisons; and sharing regulatory approaches, best practices and experiences.

The EGDLE report recognised as a key publication to understand the heterogeneous situation in national regulations regarding implementation of new equivalent dose limits for lens of the eye

Based of survey results provided by regulators from the nuclear, non-nuclear and medical communities, the report explores the implications of the significant policy change published by the ICRP in 2012 on the eye lens dose limit for occupational exposures in planned situations (e.g., recommendation to move from 150 mSv/year to 100 mSv averaged over 5 years with no single year exceeding 50 mSv).

Summary of the 2020 survey results:

• 13 out of 15 surveyed countries have revised or are in the process of revising legislation. Some countries adopted a single eye dose limit of 20 mSv/year and one country adopted a single dose limit of 50 mSv/year;
• No clear consensus emerged among responding countries regarding the demonstration of compliance with lens of the eye dose limits (e.g., how protective equipment is accounted for; how the dosimeter is worn with protective equipment; how to use surrogate dosimeters and correction factors; how to record doses);
• General consensus among countries that: (i) dosimeter should be placed “near the most exposed eye”; (ii) workplace monitoring is not acceptable to demonstrate compliance with lens of the eye dose limits; (iii) H_p(3) eye lens dosimeters are not approved and/or widely available; and (iv) eye lens dosimeters are typically approved only for photons, and not for beta and neutron radiations;
• Overall agreement that standardised and/or harmonised procedures, guidance and requirements would be beneficial around the following themes: eyewear protection and/or other protective devices, including suitability for exposure situations; harmonisation of accreditation and technical specifications for H_p(3) eye lens dosimeters; internationally accepted eye lens dosimeters and clear instructions for their use; education and training; use of personal protective equipment; use of correction factors; and standardising dosimeter placement, especially in medical applications;
• A number of opportunities for continued dialogue and information exchanges in the international fora were identified, including: the requirement for individual monitoring, and consensus on the use of eye lens dosimeters measuring personal dose equivalent H_p(3); eye lens dosimetry, with use of ISO and IEC standards to define accreditation and technical/performance specifications for H_p(3) eye lens dosimeters; dosimeter placement, taking into account personal protective equipment; and the acceptability of the use of surrogate dosimeters and correction factors.

Key takeaways from the webinar on implementation aspects

• The International Radiological Protection Association’s (IRPA) Task Group on the implementation of the Eye Lens Dose Limit conducted three international surveys on implementation aspects of the new ICRP recommendations between 2013 and 2020. A global trend towards the adoption of the ICRP recommendations was observed among those surveyed, with only around one third of responding countries having not or not yet reduced the dose limit from 150 mSv/year in the latest survey (2018-2020).
  The IRPA surveys highlight that one of the main common challenges in the implementation of the new equivalent dose limits is rooted in the costs and time/staff resources associated to the change, including to adapt procedures and protective equipment.
  The IRPA surveys also indicate that the dose levels at which routine monitoring would be considered ranges from ca. 5 to 15 mSv per year. In the medical field, ceiling suspended shields are used in more than half of the responding countries to limit exposure, whereas lead glasses, PMMA (Poly Methyl Methacrylate) glasses or full-face masks are predominant at nuclear power plants.
• The International Commission on Radiation Units & Measurements (ICRU) report 95 New Operational Quantities for External Exposure of the Eye Lens introduces a number of substantive changes, such as the closer connection of new operational quantities to protection quantities, e.g. by using the same numerical phantoms. Operational quantities will be based on absorbed doses in gray (Gy); and the calculation phantom used in ICRU 95 is the Behrens-Dietze eye model.
  Eye lens responses of available dosimeters are mostly in line with operational quantities from ICRU 95 for photons. This means that an eye lens dosimeter which has been calibrated for H_p(3) will accommodate the new quantity dose to the eye lens for photons.
• The European Radiation Dosimetry Group’s (EURADOS) working group 2 on Harmonisation of Individual Monitoring conducted an inter-comparison exercise for extremity and eye lens dose meters in 2019, covering eye lens dosimeters for H_p(3) estimation worn on the head and measuring either photons and betas or only photons. All tested eye lens dosimeters showed a satisfactory performance for photon fields. The results for beta fields were less clear (see detailed outcomes of the exercise here).
  The EURADOS working group 2 is currently working on a survey in collaboration with the International Organization for Standardization (ISO - ISO/TC85/SC2/WG19) to develop an up-to-date overview of the routine practices of individual monitoring services and assist ISO with the revision of related standards such as ISO 15382:2015 on “Radiological protection — Procedures for monitoring the dose to the lens of the eye, the skin and the extremities” (to be replaced by ISO/AWI 15382). 
• Among national examples, the Canadian Nuclear Safety Commission (CNSC) recently amended Canada’s Radiation Protection Regulations to reduce the equivalent dose limit for the lens of the eye for nuclear energy workers from 150 mSv to 50 mSv per year as of 1 January 2021. Canada is currently conducting research on eye lens dosimetry to reinforce evidence and scientific understanding in this area (e.g., see publication Current status of eye-lens dosimetry in Canada). Ongoing Canadian research projects deal with real-time dosimetry for the lens of the eye, neutron dosimetry for the lens of the eye, and photon and electron passive dosimetry for the lens of the eye.

Highlights from the discussion on research needs

• UNSCEAR’s evaluation in 2008 suggested that the sensitivity of the lens of the eye is higher than previously estimated, based on data and practical experience from different exposure situations, including the Chernobyl accident. UNSCEAR plans to start work on its first specific evaluation of the effects of ionising radiation on the lens of the eye in 2023 to improve the understanding of the potential consequences of doses received in medical, occupational or post-accident exposure situations.
  The 2020/2021 UNSCEAR report on analysis of the Fukushima Daiichi Nuclear Power Plant accident found that the discernible risk of cataracts remains uncertain, mainly due to the lack of information on whether the workers concerned are wearing masks. Future research is needed in this context.
  UNSCEAR noted that there is a lack of reliable data on the equivalent doses to the lens of the eye reported until 2019. A new international occupational exposure survey is planned within the next five years, during which better data should be collected on this topic.
• The International Commission on Radiological Protection (ICRP), in the process of revising its general recommendations (ICRP, 2007), recently published its analysis Areas of Research to Support the System of Radiological Protection (2021), without directly mentioning the eye lens. However, the ongoing Task Group on Risk and Dose Assessment for Radiological Protection of Astronauts (Task Group 115), which is working on a comprehensive framework for risk and dose assessment for radiological protection of astronauts, will review the literature on the occurrence and latency of lens opacification.
• Recent research, such as the work of the EU-funded LDLensRad Consortium highlights that epidemiological data since the updated ICRP recommendations on the equivalent dose limits to the lens of the eye for occupational exposures justifies the reduction of occupational eye lens dose limits. Radiobiological data generally points towards the same conclusion.
  There is clear evidence that radiation exposure at less than 1 Gy causes changes associated with cataract in mouse models and human lens epithelial cells. Factors such as radiation dose, dose rate, age, sex and genetic background contribute to cataract development with significant interaction effects between them.
  New data indicates that early lens changes may be better characterised as tissue reactions (as evidenced by a clear threshold) whereas longer term changes are better described as stochastic effects.
  Two recent publications (Ainsbury et al., 2021; Ainsbury et al., 2022), define the need for further research in the area of eye lens exposure, in particular to decipher biological mechanisms at low dose and dose rate, with a better understanding of the influence and interactions of factors such as age, gender and genotypes, phenotypes and eye tissues other than the lens. Exploring the link between lens and wider systemic effects is also needed; prospective molecular epidemiology is thought to be amongst ideal approaches.