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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 has since been transferred to Public Health England (PHE), who continue to manage the NWTPS.
This project is the responsibility of researchers at the Centre for Radiation, Chemical and Environmental Hazards (CRCE), which is part of PHE. 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.
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 AWE (the Atomic Weapons Establishment) 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.
The NWTPS study aimed to include all UK personnel from the RAF, the Army, the Royal Navy, AWE or UKAEA (UK Atomic Energy Authority) 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.
At the time of the last analysis, carried out in 2003, only 4,902 (23%) of the 21,357 study participants were known to have died. Some had emigrated but the majority, 14,560 (68%) were still alive. As nuclear weapons test participants were adults in the 1950s and 1960s, even the youngest of them would, by the year 2000, have been aged over 50. Those aged in their later twenties or older at the time of the earliest test, in 1952, would have been at least in their seventies by the year 2000. The life expectancy of a boy born in 1930 was less than 60 years so it is not surprising that an increasing number of former test participants are no longer alive.
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 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.
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 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.
The main finding was that test participants 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.
When compared with the control group, the test participant group had similar overall levels of age-related mortality and cancer incidence.
There was an indication that test participation may have caused a small increase in the risk of leukaemia (other than Chronic Lymphatic Leukaemia). The evidence for any such increased risk appears to have been greatest in the early years after the tests, but a small risk may have persisted in subsequent years. This indication should be treated with caution as there is not enough evidence to confirm it as fact and there is some evidence that it may have been a ‘chance finding’.
Results of other nuclear test veteran studies
A number of similar studies have investigated the long term health of veterans that participated in the US Nuclear weapons tests. The largest of these studies, the Five Series Study (published in 2000), examined approximately 70,000 soldiers, sailors and airmen who participated in at least 1 of 5 US nuclear test series in the 1950s and compared them to a control group of 65,000 comparable non-participants. The study found no significant difference in risk of death or cancer mortality for test participants when compared to the control group.
A team from Massey University in New Zealand did conduct a study of chromosome aberrations in blood samples taken from a group of 50 New Zealand test veterans. This particular study took advantage of developments in biological research techniques to carry out a project which was an entirely different approach to epidemiological studies such as the NWTPS.
The Health Protection Agency (HPA) (which has since had its functions transferred to PHE) was interested in the New Zealand research and in 2007, when the results were first presented, the HPA’s cytogenetic specialists reviewed that research. In summary, the HPA concurred with the New Zealand authors that the results of their work did indicate a statistically significant threefold increase in stable chromosomal translocations for veterans (compared to their control group) and also agreed that it would be possible to ascribe this increase to radiation exposure. However, the presence of unstable aberrations left open the question of whether all of the dose was delivered around the time of the nuclear weapons tests.
PHE 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 users who require various credentials and authorisations to be able to access the database. Personal identifiable information collected for the NWTPS is not made available for any other purpose.
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. It is possible for participants to opt out of the study by contacting the PHE Radiation Epidemiology Group via email: firstname.lastname@example.org.
The study was considered, and approved, by the British Medical Association Central Ethical Committee in 1983. In 2016, the study was assessed and gained favourable opinion by a NHS Research Ethics Committee. The study has also received support from the Confidentiality Advisory Group (CAG). The CAG considers applications for accessing personal data without consent under section 251 of the NHS Act 2006 and the Health Service (Control of Patient Information) Regulations 2002 and provides recommendations to the Health Research Authority.
Independent oversight and review
Researchers at PHE 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. In order to further demonstrate independence, the most recent analysis was overseen by an independent advisory group led by Professor Nicholas Wald, FRS. Details of the advisory group can be found in the analysis report.
When reports are published in reputable scientific journals, those reports are first examined by independent experts who will provide a view on the reports, the findings and the work undertaken. If they think that the work has not been undertaken properly they will say so. This is called a peer-review process and such reputable journals will only publish papers which are accepted by the independent experts it consults. The 3 NWTPS analysis projects completed so far have been reported in 2 highly respected journals – the British Medical Journal, and the Journal of Occupational and Environmental Medicine.
The NWTPS study and database work undertaken by the PHE (and formerly the NRPB) are funded through a contract with the Ministry of Defence (MoD).
The NRPB reports and papers give some background detail and provide references to other documents. Further information is also available through the MoD website. Enter British Nuclear Test Programme in the search box.
Comprehensive reports have been published with full explanations of the work undertaken in this study, including details of data collection, data verification, statistical analyses, interpretation of results and the conclusions drawn.
Since 1983, the NRPB (now PHE) researchers have completed 3 full epidemiological analyses of the UK Participants in the UK Atmospheric Nuclear Weapons Tests and Experimental Programmes. The first epidemiological analysis was completed in 1988 and described the findings based on follow-up to 1983. A subsequent analysis, reported in 1993, described findings based on follow-up to 1990 and a third analysis, which considered follow-up to the end of 1998, was published in 2003. Each of these analyses was reported in a full report published by NRPB and also in a shorter paper which was published in a scientific journal (and as such was reviewed by independent scientists before publication).
The most recent publications were completed in 2004 when 2 review papers describing the NWTPS epidemiological studies and the results were published in the scientific journal, the Journal of Radiological Protection.
Review Papers 2004
Epidemiological studies of UK test veterans: I General Description. Journal of Radiological Protection 24 199 to 217; Kendall G M, Muirhead C R, Darby S C, Doll R, Arnold L, O’Hagan J A.
Epidemiological studies of UK test veterans: II Mortality and cancer incidence. Journal of Radiological Protection 24 219 to 241; Muirhead C R, Kendall G M, Darby S C, Doll R, Haylock R G E, O’Hagan J A, Berridge G L C, English M A, Hunter N.
Third Analysis (2003)
Follow up of mortality and incidence of cancer 1952-1998 in men from the UK who participated in the UK’s atmospheric nuclear weapons tests and experimental programmes. Occupational and Environmental Medicine, 60, 165 to 172. Muirhead C R, Bingham D, Haylock R G E, O’Hagan J A, Goodill A A, Berridge G L C, English M A, Hunter N and Kendall G M.
Mortality and Cancer Incidence 1952-1998 in UK Participants in the UK Atmospheric Nuclear Weapons Tests and Experimental Programmes. Chilton, NRPB-W27. Muirhead C R, Bingham D, Haylock R G E, O’Hagan J A, Goodill A A, Berridge G L C, English M A, Hunter N and Kendall G M.
Second Analysis (1993)
Further follow-up of mortality and incidence of cancer in men from the United Kingdom who participated in the United Kingdom’s atmospheric nuclear weapon tests and experimental programmes. British Medical Journal, 307, 1530 to 1535. Darby S C, Kendall G M, Fell T P, Doll R, Goodill A A, Conquest A J, Jackson D A and Haylock R G E.
Mortality and cancer incidence 1952-1990 in UK participants in the UK atmospheric nuclear weapon tests and experimental programmes.Chilton, NRPB-R266 (London, HMSO). Darby S C, Kendall G M, Fell T P, Doll R, Goodill A A, Conquest A J, Jackson D A and Haylock R G E. (1993b)
First Analysis (1988)
A summary of mortality and incidence of cancer in men from the United Kingdom who participated in the United Kingdom’s atmospheric nuclear weapon tests and experimental programmes. British Medical Journal, 296, 332-338. Darby S C, Kendall G M, Fell T P, O’Hagan J A, Muirhead C R, Ennis J R, Ball A M, Dennis J A and Doll R.
Mortality and cancer incidence in UK participants in UK atmospheric nuclear weapon tests and experimental programmes. Chilton, NRPB-R214 (London, HMSO). Darby S C, Kendall G M, Fell T P, O’Hagan J A, Muirhead C R, Ennis J R, Ball A M, Dennis J A and Doll R.