Genetic and Cytogenetic Assessment of British nuclear test veterans and their families

Frances Daley, Julia Michalek, Christine Rake, Laurette Bukasa, Clare Gilham, Julian Peto, Martin Scholze, Alex Moorhouse, Yuri Dubrova, and Rhona Anderson

Purpose of Study

We are using cytogenetic and whole genome sequence techniques to analyse samples obtained from nuclear test veterans and one of their children. The purpose of the study is to look for any genetic changes and if found, to ask if these are similar or different to that found in a control family population.

Background to Study

The British Government undertook a series of atmospheric nuclear weapons tests at various sites in Australia and the South Pacific between 1952 and 1958. Associated with these tests was an experimental programme in which radioactivity was dispersed into the environment. This programme ended in 1963 although operations continued through to 1967. Additionally, UK personnel participated in a series of American tests based at Christmas Island in 1962. It is estimated that over 20,000 UK servicemen participated in at least one of these British and American tests.

An ongoing concern within the nuclear test community has been whether veterans of these programmes could have received sufficient radiation exposure to cause genetic damage in them. Genetic damage can increase the risk of developing various diseases. This concern extends to whether they might also have passed on genetic alterations to their children, thereby potentially affecting their family’s health.

Aim and Rationale

The aim of this study is to determine whether there is any evidence of genetic change in veterans of historical nuclear test sites and/or their children when compared to control family groups. If service personnel were exposed to radiation at these nuclear test sites then cytogenetic markers consistent with such exposures may still be detectable within their peripheral blood cells. Additionally if the genome of their children is structurally or numerically altered then we should be able to identify these changes using cytogenetic and whole genome sequencing techniques. If no differences are seen between test and control groups then this will be useful and reassuring knowledge for the nuclear community.

The primary objectives of this study are:

(i) to ask if there is any cytogenetic evidence that suggests historical radiation exposure in nuclear test veterans
(ii) to ask if there is any evidence, using both cytogenetic and whole genome sequence methods, for any transgenerational genetic effects in 1st generation children

Cytogenetic analysis

We will analyse cells isolated from whole blood using a range of different cytogenetic techniques (Figure 1). The research data generated will comprise frequencies of occurrence of different categories (types) of chromosome aberrations and will be informative for:

(1) estimating radiation dose (dosimetry).
(2) estimating type (or quality) of radiation exposure.
(3) determining the occurrence of any genomic instability.

We will use these research cytogenetic tests to examine for any differences between the test and control populations.

      

Figure 1: Two-colour FISH reveals a stable reciprocal translocation between a red and green chromosome, all other chromosomes in metaphase cells are stained blue (Panel A). 24-colour M-FISH shows a metaphase cell with a complex chromosome aberration; abnormal chromosomes are revealed by having more than one colour down their length (depicted as a colour switch) (Panel B). Giemsa stained metaphase cell showing unstable, potentially newly arising, abnormalities such as dicentrics and fragments (Panel C).

Whole genome sequence analysis

We will sequence DNA samples and estimate the relative proportions of mutated DNA detected in test and control populations. We will characterise the spectra (type) of any newly arising mutations which are found in the child’s DNA sequence and using a range of bioinformatics tools, will question the potential impact of any identified mutations. This work will allow us to estimate the effects of any paternal (from the father) exposure on mutations induced in the human germline.

Who will be studied?

We are identifying armed forces veterans from military records of personnel serving in the Tropics during the 1950s and 1960s. In total we will include 100 military veteran family trios (military veteran, their spouse or partner, and a biological child they have together). Half the veterans in the study will have been at British nuclear test sites and half (the control group) will have served elsewhere in the tropical region.

What does the study involve?

Invited families who are recruited to the study will be contacted by the study team and arrangements made to have a small blood sample collected. The blood sample will then be sent to Brunel University London for analysis.

How are we selecting veterans?

The test veterans will be selected from the ‘Nuclear Test Veteran Cohort,’ the largest known database of test participants. This cohort was originally made up of over 20,000 veterans verified to have been present at one or more nuclear test sites and control veterans verified not to have been present at test sites. We have been approved to use a method of ‘stratified random sampling’ (Figure 2) to restrict our focus to those veterans most likely to have been exposed to radiation. We reason that if there are any differences in the genetic makeup of veterans, we are most likely to detect them using this particular sampling approach.

We will be looking for genetic differences set against a lifetime of exposure to a global background of radiation from a variety of sources including radon gas in the environment, diagnostic exposures as well as other confounding effects.

Figure 2 : Our randomised stratified approach is designed to select veterans who, based on information available, were most at risk of having been exposed to radiation.

Can I volunteer for the study?

Some studies, such as this one, are designed to invite specific groups of people to participate, but means that individuals cannot request to join. In this study we have purposely designed to select veterans based on their potential for exposure. We have focussed upon a subgroup who were the most likely to have been exposed, for example those who carried out specific high risk duties such as cleaning contaminated aircraft.

This stratified random sampling approach, as shown in Figure 2, unfortunately prevents individuals from proactively volunteering. The approach we are taking lessens the impact of any selection bias that would occur if we did accept proactive volunteers. A way of understanding selection bias might be to think back to the Scottish referendum. For example, if the last 1 million votes cast on polling day were excluded (out of the 3.6 million votes cast), the poll would have been biased in favour of those who chose to vote early. Exclusion of the last 1 million votes cast would represent a selection bias (Figure 3).


Figure 3 – To explain selection bias, here is an imaginary scenario regarding the Scottish Independence Referendum

Similarly, were we to enrol volunteers on a first come basis, volunteer selection would be biased in favour of the “earlies” at the expense of the “lates”. This would mean that the sample of veterans enrolled would not be a random sample and therefore would not fairly represent the subgroup of veterans identified as having the highest potential exposure risk. Accepting volunteers who approach us first will also raise issues around the need to verify military service records and their potential for exposure retrospectively, and having to subsequently identify and verify a matched control. Instead, in our approach we are randomly inviting veterans from a pre-assembled database of nuclear test veterans we have already identified as having “highest potential for exposure”, and who are already carefully matched with control veterans.

If I receive a letter and agree to participate will I definitely be recruited into the study?

No. First, we will need to verify eligibility criteria for you, your partner and your child. Once that is confirmed we will then need to obtain written consent from you all.

Shall I contact my GP to ask to be included in the study?

No. Your GP cannot ask for you to be included in the study, however you could enquire if they have received any invitations from our study team in case they have yet to forward this to you.

Can I refuse to participate or withdraw at any time?

Yes. If you do not wish to be contacted to participate or, if you wish to withdraw you may do so at any time. Please contact the study team at the London School of Hygiene & Tropical Medicine on telephone number 020 7927 2722 or email VETS@LSHTM.AC.UK to advise accordingly.