A cytogenetic study of New Zealand nuclear test veterans : the COMET assay : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University

Abstract

Between 1952 and 1958, forty thousand troops witnessed or assisted in the detonation of nuclear weapons in and around Australia and Christmas Island. Of these forty thousand troops there were 550 sailors from New Zealand; the remainder were mainly from Australia or Britain, together with a Fijian contingent. Since the end of this test series, the participants have maintained that they were exposed to radiation that has affected their health. The New Zealand test veterans say that their lifespan has been reduced by at least 10 years and there have been an unusually high number of genetic disorders among them and their children. The possible genetic effects of this radiation exposure have never been fully investigated. One of the most popular techniques for detecting DNA damage is the single-cell gel electrophoresis assay (SCGE), also known as the COMET assay. The COMET assay was used throughout this study to determine if veterans of the Operation Grapple tests have longterm genetic effects as a result of their participation. The COMET assay measured three factors to determine the overall genetic damage in these veterans: the tail length; the tail moment; and the Olive tail moment. Only the tail length had a significant amount of difference after a comparison with a control group was conducted (P=0.046). However, the mean genetic damage in these veterans was lower than that of the control group. It is unclear if this result is due to an anomaly in the data, or due to some other complex factor. An epidemiological analysis revealed a possible link between the mortality of these veterans and the number of weapons detonated. The collection of these one hundred samples, not including re-collections, from several areas of New Zealand became a logistical nightmare. To minimise this problem a pilot study was also incorporated into this research to determine if blood samples could be cryopreserved for extended periods of time without an accumulation of genetic damage due to the freezing process. The COMET assay was also used to determine this damage. The cryopreservation of these samples induced extensive genetic damage. Only 7 from the total of 60 frozen samples were retrieved with a level of damage that was not significantly different from the original, unfrozen sample (P=>0.050). It appears that the routine use of cryopreserved blood samples for cytogenetic testing is not possible at this time and further study is required.