Guidance

Nuclear weapons test participants study: information sheet

Updated 14 October 2022

Background

In the years after the UK atmospheric nuclear weapons tests, there were suggestions that the health of participants had suffered.

In 1983, scientists from the National Radiological Protection Board (NRPB) and the Imperial Cancer Research Fund (now Cancer Research UK) were commissioned by the Ministry of Defence (MoD) to carry out an independent epidemiological study of participants in the UK atmospheric nuclear weapons tests, both in the Pacific and in Australia.

The NRPB had expertise in epidemiological research of radiation-exposed populations and an interest in furthering the knowledge of health effects of human exposure to radiation. The NRPB was a non-departmental public body, able to conduct research and to publish findings independently.

The combination of the database, statistical and epidemiological expertise of the researchers with access to NRPB colleagues such as radiation physicists, chemists and biologists was able to cover the wide range of issues that were relevant to this research.

The Nuclear Weapons Test Participants Study (NWTPS) began in 1983 and is a long-term follow-up study of the health of UK personnel who were present at UK atmospheric tests conducted between 1952 and 1967. The functions of the NRPB have since been transferred to the UK Health Security Agency (UKHSA), who continues to manage the NWTPS.

Study team

This project is the responsibility of researchers in the Radiation, Chemical and Environmental Hazards Division of UKHSA. The research team consists of database staff, statisticians and epidemiologists who manage this study alongside other studies that examine the health effects of radiation, such as The National Registry of Radiation Workers.

Study design

The NWTPS is an epidemiological study. Epidemiological studies collect data on people’s exposure to particular events and also collect data on the occurrence of particular diseases in those people. Statistical analysis compares those exposed with those who are not exposed to see if there is any difference in the pattern of diseases.

The NWTPS takes a group of people who were present at the UK atmospheric nuclear tests and compares them with the general population and with another similar group of people who were not at the tests (a control group). The study examines whether there are significant differences in mortality causes or cancer incidence between these groups.

Participants in the nuclear weapons test programme would have differed in some ways from men of the same age in the general UK population. For example, test participants needed to have been fit enough to be selected for overseas service, and they would have experienced a different lifestyle during their period in a tropical or desert environment.

Consequently, as well as comparing mortality and cancer rates among test participants with the corresponding national rates, comparisons were also made with the control group.

The control group contains roughly the same number of men as the participants’ group and, apart from not participating in the tests, the controls were chosen to have similar characteristics to the participants.

For test participants in the armed forces, the controls were selected from service personnel who served in tropical or sub-tropical areas other than the test locations around the time that the tests were taking place.

For the Atomic Weapons Establishment (AWE) test participants, the controls were chosen from other men working for AWE at around the same time as the weapons tests.

The 22,333 men in the control group were very similar to the participants with respect to the split between services, ranks or social class, year of birth, year of enlistment or employment and year of discharge or end of employment.

Study populations

The NWTPS aimed to include all UK personnel from the RAF, the Army, the Royal Navy, AWE or the UK Atomic Energy Authority (UKAEA) who had had potential for exposures to radiation as a result of involvement in the UK atmospheric nuclear weapon test programmes in Australia or the Christmas Island region between 1952 and 1967. There is, however, no complete list of those who visited test sites during the atmospheric nuclear test programme.

The study group was identified following the examination of an extensive range of documents which had been compiled during the test programme of the 1950s and 1960s. These included planning documents, technical reports, health physics records, Royal Navy ships’ ledgers and RAF operational record books as well as service records and other documents.

Unfortunately, however, there was never any complete log of those involved so it was not possible to check against such a list.

Employees of many other organisations were involved in the test programmes (the Meteorological Office and the Merchant Navy for example), but the records available to the researchers in 1983 were not sufficiently complete to allow identification of the relevant individuals and so these groups were not included in the NWTPS study group.

Foreign personnel were not included as health follow-up for non-UK personnel could not be ascertained in the same way as for UK personnel.

Additionally, it was also decided to exclude the very few women who had taken part in the tests as the number was too small for useful analysis.

The exclusion of records from the study does not mean that the individuals are necessarily different to those included in the study, rather that the data was not sufficiently complete to add value to the epidemiological work.

There is a dilemma in defining the population to be studied. On the one hand, if it included only those clearly likely to be exposed to radiation (for example aircrew sampling the radioactive plumes from the explosions), then it would exclude other groups who should also be regarded as bona fide test participants. On the other hand, including as many as possible of those involved in the tests would inevitably include some groups who had little real chance of having been exposed and might dilute away any excess of disease in those most at risk.

To try to deal with this issue, the investigators took a wide definition of test participation but also carried out special analyses of those sub-groups which might have been at increased risk. A fuller description is available in the published reports.

The 2003 report details the study cohort of 21,357 participants and completeness checks undertaken by the researchers indicate that this represents 85% of the total eligible study population. It was not necessary to include all test participants in the study, though it was desirable that as many as possible of them were included.

A larger study population increases the ability to detect any harmful effect of test participation. It was, however, important for the study team to ascertain whether the 15% not included were not significantly different to those included with regard to their potential exposure to radiation and their health.

The NRPB researchers were also able to assemble a list of test participants from sources independent of MoD. When the researchers looked within this independently compiled list, they found that the health experience of those also found in the MoD records was similar to the health experience of the 15% who were not included in the MoD records. This provided powerful evidence against the idea that less healthy individuals were less likely to be included in the study population.

Further details on the work undertaken to investigate potential biases is discussed in detail in the published reports.

The researchers will not add additional records to the study cohort because they do not want to introduce ‘bias’ to the study. For example, if they added details of those men who confirmed that they had been present this could distort the findings because those that had already died could not contact the researchers.

Service information

The NWTPS database holds information to identify the test participants (including names, service numbers and dates of birth), information about their test participation (such as name of test and test sites). The information on the database was collated from a variety of sources but the main sources were the contemporary documents detailing test participation, service or employment.

The ‘Blue Books’ were compiled between 1981 and 1982 by AWE using information from documents that had been written during the period that the nuclear weapons test programme was undertaken. It is not a complete list of people who attended the test sites (no complete list was ever compiled).

In 1982, the list that had been compiled by AWE was sorted (by name within service) and printed off in a series of documents which were bound in blue covers and became known as ‘the Blue Books’. The foreword to the listing states that it is a ‘summary provisional listing’ and that ‘the listing is not claimed to be free from errors, incorrect assertions or omissions’.

The ‘Blue Book’ data was used by NRPB as one of the sources of information for identifying the NWTPS study participants. The NRPB researchers had access to the original documents that AWE had used to compile the ‘Blue Books’ as well as additional information resources that were identified as the NRPB work progressed. The researchers were careful to ensure that all the documents used dated from the period of the test programme (‘contemporary documents’) to ensure that no bias was introduced into the study cohort.

The sources are listed in the NRPB reports and include health physics documents, planning documents and trials reports.

The NWTPS 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 for data or to complete a questionnaire. This approach both reduces the impact on the individual as well as reducing any risk of bias in response from study subjects.

Researchers were faced with a huge task as there had never been a complete list of all those that had attended the nuclear weapons tests. The study team had to rely on searches of a vast number of documents dating from the time of the weapons tests to identify the test participants.

Many names appeared on more than one document but it became clear that some people were not listed on any of the main documentation and further searches, including searches of service records, were undertaken.

The NWTPS published reports and papers describe, in some detail, the work that was undertaken to identify the study participants and the work that was also undertaken to verify the information collected and its completeness.

Radiation exposure

All of the world’s population is exposed to radiation to some extent as background (naturally occurring) radiation affects us all.

It has not always been appreciated that the contemporary records indicate that relatively few test participants received any measurable radiation dose as a result of the tests. Some participants have thought that the flash of intense light that accompanied some explosions and could be detected through their fingers with their hands held over their eyes, was a dose of X-rays. In fact, X-rays are not visible and it was just intense light that was visible through their hands.

Some test participants were exposed to higher levels of radiation as a result of their work within the test programme and these groups of people were looked at in specific analysis sub-groups (detailed in published reports).

Health physics records were made available to study researchers. These provided lists of individuals who had been issued with film badges to record their possible exposure to external radiation and details of any doses above the threshold of detection which had been incurred.

The published NWTPS reports and papers provide more detail about what is known of the monitoring regime at the tests but the researchers were content that the data available to them was sufficient and they were also happy that their study design was such that significant unreported exposures would also have been apparent to them.

Follow-up information

Information about health events (such as date and causes of death, and date and details of cancer incidence information) are provided to the study team by the NHS Central Registers (NHSCRs). The NWTPS examines all causes of death, whether from cancer or any other disease or condition.

The NWTPS reports show more details.

The UK national registries are internationally recognised as an invaluable resource in providing excellent and unbiased information about deaths and cancers in the UK population. There is no better resource available for this type of study.

Before 1971, there was no UK-wide system for systematically recording details relating to patients who were diagnosed with cancer. From 1971, as cancer treatment improved and a greater percentage of patients recovered from cancer, regional cancer registries began to work together to collate a national cancer registry. This has allowed the NWTPS to analyse cancer incidence (as well as mortality) from when data became available in 1971.

Information on the health of study participants is obtained only from the national records indicated above, it does not require specific examination of participants’ body tissues. The study team will not seek to gain access to body tissues from participants or control group members.

Analyses

To date, there have been 4 analyses, the result of which have been published in the peer reviewed scientific literature. These were based on following the cohort up to 1983, 1990, 1998 and 2017 respectively.

Over all the analyses, when compared with the control group, the test participant group had similar overall levels of aggregated mortality and cancer incidence.

In addition, test participants and controls had, in general, a greater life expectancy than members of the general UK population. This ‘Healthy Worker Effect’ (or ‘Healthy Soldier Effect’) reflects the fact that a group of people who have been employed will (overall) be healthier than the general population because the general population will include the chronically sick who are unable to work.

Data security

UKHSA is the data controller for the NWTPS database. The NWTPS database is registered under the Data Protection Act and information security is taken very seriously by the study team.

The database is held on a secure system and is accessible only to authorised employees of UKHSA who require various credentials and authorisations to be able to access the database. The study has a privacy notice.

Study participation

The study was set up in 1983. If it had been necessary to have permission from each individual who had been involved in the tests programme, it would have meant that the researchers needed to trace and contact over 20,000 people. As some of those men were already dead, they would not have been able to reply.

Additionally, it is known that if only those that agreed were included in the study, there would have been a higher response rate from those that had been ill than those that had not.

Both of these issues would have made it far more difficult to analyse the results of the study as it would have been necessary to take account of the impact of those issues.

The nuclear test veterans’ organisations were involved in discussions with the researchers as the study was developed and the progress and the results of the work have been openly published and widely publicised.

Ethical approval

The study was considered, and approved, by the British Medical Association Central Ethical Committee in 1983. In 2021, the study was reassessed by an NHS Research Ethics Committee and gained favourable opinion to continue for an additional 5 years.

Also in 2021, the study was re-assessed and received approval to continue to process personal data without consent under Regulation 3 of the Health Service (Control of Patient Information) Regulations 2002 by the UKHSA Caldicot Guardian.

Independence of the study

Researchers at UKHSA and its predecessor, the NRPB, are independent and do not work for the MoD. All of the researchers’ reports have been published, in full, and additional papers have been published in respected peer-reviewed scientific journals. The reports and papers are written by the researchers and are not subject to MoD approval.

Funding

The NWTPS study analyses, database maintenance and data collection are undertaken by UKHSA (and formerly the NRPB) and funded through a contract with the MoD.