Mortality and cancer incidence of Australian participants in the British nuclear tests in Australia

OBJECTIVES

To investigate the mortality and cancer incidence of Australian nuclear test participants, and to identify any association with exposure to ionising radiation.

METHODS

A retrospective cohort study was carried out in which the mortality and cancer incidence rates of participants (n = 10,983) were compared with rates in the general male Australian population. Dose reconstructions were carried out by a panel of health physicists. Mortality and cancer rates were compared with the general population and between groups of subjects categorised by assessed radiation exposure.

RESULTS

All-cause mortality was not raised. Mortality and incidence were significantly raised for cancers of the head and neck, lung, colon and rectum, and prostate, and for all cancers combined. For oesophageal cancer, melanoma, all leukaemias and non-chronic lymphatic leukaemia (non-CLL leukaemia), incidence was significantly raised, but mortality was non-significantly raised. No association was found between radiation exposure and overall cancer incidence or mortality, or with any cancer or cancer deaths occurring in excess.

CONCLUSIONS

There is no evidence that the excess cancers and cancer deaths were caused by radiation exposure at the test sites. Possible contributing factors are high smoking prevalence and demographic differences from the Australian population with whom rates were compared. Asbestos is a likely contributor to some cancers in naval personnel.

Differential modulation of Alzheimer's disease amyloid beta-peptide accumulation by diverse classes of metal ligands

Biometals have an important role in AD (Alzheimer's disease) and metal ligands have been investigated as potential therapeutic agents for treatment of AD. In recent studies the 8HQ (8-hydroxyquinoline) derivative CQ (clioquinol) has shown promising results in animal models and small clinical trials; however, the actual mode of action in vivo is still being investigated. We previously reported that CQ-metal complexes up-regulated MMP (matrix metalloprotease) activity in vitro by activating PI3K (phosphoinositide 3-kinase) and JNK (c-jun N-terminal kinase), and that the increased MMP activity resulted in enhanced degradation of secreted Abeta (amyloid beta) peptide. In the present study, we have further investigated the biochemical mechanisms by which metal ligands affect Abeta metabolism. To achieve this, we measured the effects of diverse metal ligands on cellular metal uptake and secreted Abeta levels in cell culture. We report that different classes of metal ligands including 8HQ and phenanthroline derivatives and the sulfur compound PDTC (pyrrolidine dithiocarbamate) elevated cellular metal levels (copper and zinc), and resulted in substantial loss of secreted Abeta. Generally, the ability to inhibit Abeta levels correlated with a higher lipid solubility of the ligands and their capacity to increase metal uptake. However, we also identified several ligands that potently inhibited Abeta levels while only inducing minimal change to cellular metal levels. Metal ligands that inhibited Abeta levels [e.g. CQ, 8HQ, NC (neocuproine), 1,10-phenanthroline and PDTC] induced metal-dependent activation of PI3K and JNK, resulting in JNK-mediated up-regulation of metalloprotease activity and subsequent loss of secreted Abeta. The findings in the present study show that diverse metal ligands with high lipid solubility can elevate cellular metal levels resulting in metalloprotease-dependent inhibition of Abeta. Given that a structurally diverse array of ligands was assessed, the results are consistent with the effects being due to metal transport rather than the chelating ligand interacting directly with a receptor.

Radon daughter exposures at the Radium Hill uranium mine and lung cancer rates among former workers, 1952-87

The aim of this historical (retrospective) cohort study was to investigate the relation between occupational exposure to radon daughters and subsequent mortality from lung cancer. Participants were former workers from the Radium Hill uranium mine, which operated in eastern South Australia from 1952 to 1961. A total of 2,574 workers were identified from mine records. Exposures to radon daughters were estimated from historical records of radon gas concentrations in the mine and from individual job histories. Exposures of underground workers were low by comparison with other mines of that period (mean 7.0 Working Level Months [WLM], median 3.0 WLM). Thirty-six percent of the cohort could not be traced beyond the end of employment at Radium Hill. Among those traced to the end of 1987, lung cancer mortality was increased relative to the Australian national population of the period (Standardized Mortality Ratio = 194, 95 percent confidence interval [CI] = 142-245). Compared with surface workers, lung cancer mortality was markedly increased in the underground workers with radon daughter exposures greater than 40 WLM (relative risk = 5.2, CI = 1.8-15.1). From the available information, we conclude that this increase is unlikely to be due to differences in smoking habits or other confounders. Taken together with the findings from other occupational studies, these results support current moves towards more stringent radiation control in the workplace, and underline the importance of research into the possible effects of domestic radon exposures.