Research and analysis

National registry for radiation workers: guidance

Updated 22 August 2024

Background

National guidelines and regulations restricting occupational exposure to ionising radiation are set by the Health and Safety Executive (HSE) to protect the health of workers in the UK.

The guidelines are largely based on estimates of the long-term health risks following exposure to ionising radiation obtained from studies of survivors of the atomic bombings of Hiroshima and Nagasaki in 1945 and from certain groups exposed to radiation for medical reasons.

However, there is uncertainty about whether the radiation risks seen in the atomic bomb survivors are applicable to UK radiation workers and the general public.

First, the atomic bomb survivors received a single external radiation dose over a very short time period (up to several seconds). The amount of dose received was mainly influenced by an individual’s distance from the explosions, but many individuals received very high doses.

In contrast, nuclear workers are generally exposed to very low doses over long periods of time, ranging up to many years. It is not clear if a dose received by a UK worker at a low exposure rate over many years has the same capacity to induce disease as the same dose received at a very high rate over a short period of time.

Second, the underlying rates of some common diseases among the atomic bomb survivors are significantly different to those in UK workers and the public. This adds to the uncertainty about extrapolating the radiation-related risk estimates for these diseases to UK workers.

As a result of these 2 issues, a need was identified to directly estimate radiation risks among those in the UK exposed occupationally and the public so that these estimates could be compared to those derived from the atomic bomb survivors.

For this purpose, the National Radiological Protection Board (NRPB), which had the necessary expertise to investigate the effects of radiation on health, set up the National Registry for Radiation Workers (NRRW) study in 1976.

The aim of the NRRW study is to investigate the effects of long-term occupational exposure to radiation on the health of workers and assess whether radiation protection regulations and guidelines provide an adequate level of protection for UK radiation workers.

The NRPB became a part of the Health Protection Agency (HPA) in 2005. HPA transferred all its functions to Public Health England (PHE) in 2013, and in turn, the part of PHE that operated the NRRW was transferred to the UK Health Security Agency (UKHSA) in 2021.

As many of the early workers are reaching old age and the end of their lives, information is being added to the study about the cancers they develop and ultimately their cause of death. This means the study can now provide high-quality evidence about the risks of low dose radiation exposure to the UK population to ensure the UK radiation protection regulations are appropriate to protect occupationally exposed workers and the public.

This is particularly important as few of the Japanese atomic bomb survivors remain alive and so that source of information on risk from radiation exposure will provide little new useful evidence in the future.

Study team

The team consists of database staff, statisticians and epidemiologists from the Radiation Effects Department within the Radiation, Chemical and Environmental Hazards Division of UKHSA, based at Chilton in Oxfordshire.

Study design

The NRRW is an epidemiological study. Such studies analyse the distribution (who, when, and where) and determinants of health and disease conditions in a population.

The NRRW links workers’ occupational radiation exposure with outcome data, such as cause of death or cancer incidence details. Statistical analyses then consider what conclusions may be drawn concerning risks of mortality and cancer incidence from comparisons between the study group (or ‘cohort’) and the national population, and between groups of workers with different levels of radiation exposure.

It is an entirely records-based study that does not require any ongoing contact with the participants.

Study population

The study population consists of workers from a wide range of industrial employer organisations. The largest of which is the Ministry of Defence (MoD) followed by workers from sites formerly managed by British Nuclear Fuels Ltd (BNFL), workers employed by the UK atomic energy authority (UKAEA) and workers employed at UK nuclear power generation sites.

Currently the study does not contain workers from the health care sector.

The study has collected data from radiation workers who were in employment since 1976 (when the NRRW was set up) and also retrospectively for those who started employment before 1976.

The study now holds details of over 270,000 workers and continues to recruit new workers.

Employment and follow-up information

Employers provide records of employment episodes, occupational exposure to ionising radiation and some personal identifying data including name, date of birth, sex, National Insurance number and National Health number.

The National Records for Scotland provides mortality and cancer incidence data for workers living in Scotland.

The route by which follow-up information is obtained about participants living in England and Wales has changed several times over the life of the study.

Currently, the UKHSA Office for Data Release (ODR), which manages secondary use access for UKHSA studies to the English National Cancer Registry and Office for National Statistics mortality data provides mortality data for England and Wales and cancer incidence data for England.

Welsh cancer incidence data is collected directly from the Welsh cancer registry.

Study participation

The NRRW is a records-based study, which means that details for each individual are drawn from existing records and do not require individuals to be contacted to collect data. This approach both reduces the impact on the individual as well as reducing the risk of bias in the study due to the response of participants.

The NRRW has always operated an ‘opt-out’ policy by which any individual may request that their details are not included in the study. Over the 45 years operation of the study, the number of people choosing to take this option has been very low.

This policy will ensure that the research findings, which are intended to inform both radiation workers themselves as well as the scientific and medical community, will be more valid than if a significant number of workers opt out.

The estimated opt-out rate for the NRRW has been around 1% for many years. It is possible for participants to opt out of the study at any time by contacting the UKHSA Radiation Epidemiology Group via email: radiationworkerepidemiology@UKHSA.gov.uk

Information governance

UKHSA is the data controller for the NRRW study and the sole data processor. The data is contained in a secure database system that is held on the UKHSA IT infrastructure. It is accessible only to authorised users, who require various credentials and authorisations to be able to access the database.

Personal and identifiable information collected for the NRRW is not made available for any other purpose.

In 1981, the British Medical Association Ethics Committee granted ethical approval for the NRRW. In 2016, an NHS Research Ethics Committee also assessed the NRRW and provided a favourable opinion for the continuation of the study. In 2021, the study was granted an extension of the ethical approval for a further 5 years.

The study team has the legal authority to process personal identifiable data about participating workers without positive consent. For workers who live in England and Wales this has been provided by the UKHSA Caldicott Guardian who has the authority to grant such permission under regulation 3 of the Health Service (Control of Patient Information) Regulations 2002 for studies undertaken for public health benefit.

The study has been submitted to a Public Benefit Privacy Panel review for National Records for Scotland to receive mortality and cancer incidence data about Scottish residents in the study.

The study passed this review and now has permission to process personal data about cohort members who live in Scotland and to receive follow-up data about these people. This permission lasts for 5 years and is renewed periodically.

The study team has also concluded a data sharing agreement with the Northern Ireland Cancer Registry, maintained by Queen’s University Belfast to obtain mortality and cancer incidence data for Northern Ireland residents.

The team maintains a close relationship with the study stakeholders. A data sharing agreement has been set up with each employer that has currently employed workers in the NRRW.

A new data governance group was set up in 2022. This group was established to provide governance and oversight of the epidemiology work proposed, using data from the study.

The study privacy notice is published on this site.

Results

The statistical analyses of data extracted from the cohort database are published in scientific journals and formerly NRPB reports. The publications only contain results of a statistical nature and do not allow the identification of any particular individual.

The NRRW analyses to date have shown that UK radiation workers have a greater life expectancy and healthier life than the UK general population. This is expected and can be explained by the so-called ‘healthy worker effect’, where occupational groups often display better health than the general population because those who are chronically ill are less likely to be at work. Nonetheless, the study has observed small increases in the risk of some cancers with increasing radiation exposure.

The health risk estimates derived from the NRRW have shown consistency with those used by international bodies setting radiation protection standards. This indicates that the measures currently in place in the UK concerning workplace radiation exposure should provide adequate protection of the health of workers from cancer risk. It also provides the same reassurance to members of the public for whom permitted exposure levels under the regulations are lower than for workers.

As the study continues to accumulate more information on cancer incidence and the causes of death of workers, it will increase its statistical power and provide more precise information about radiation risks.

Details of specific peer reviewed publications are provided.