BERKELEY, CA (UroToday.com) - The Wismut cohort of German uranium miners, as recently profiled,[1] is interesting from at least three different perspectives: historically, for research into the detrimental health effects of ionising radiation, and for general epidemiological research.
From a historical perspective, it is interesting to note that the German Wismut former mines, located in Saxony and Thuringia, were not the mines that supplied Marie Curie and Werner Heisenberg with pitchblende-containing uranium for their high-profile research. The German mines are geographically located near these Czech “Joachimsthal” mines just north of the border between these two countries. The Soviet Red Army was the first to realize, in the 1940s, the full potential of this area of Germany for supplying uranium. Most probably, with this realization in mind, the Soviet leaders skilfully and successfully negotiated their claim to this region during the annexation of Germany at the end of the World War II. Subsequently the uranium seams were immediately located and mined and began to amply supply the Soviet Union’s atomic industry in 1946. The name “Wismut,” which is the German word for Bismuth, was chosen by the Soviets to distract from the real nature of their mining activities at that time.
Approximately 400 000 persons worked at the Wismut company at some period between 1946 and 1990. After German reunification, the German Federal Ministry for the Environment maintained the Wismut health data archives, thereby enabling the establishment of the cohort. Up to the publication of the article on prostate cancer mortality risk in relation to working underground, by Walsh et al.,[2] the previous Wismut cohort papers had all been connected with radiation-epidemiology. The radon-associated risks of lung cancer[3, 4] - also considered smoking[5, 6] and silica exposures,[7] extra-pulmonary cancers,[8, 9, 10] cardiovascular diseases[11] and radiation-related leukaemia risks[12] - have been investigated.
The idea of investigating prostate cancer mortality risk in relation to working underground occurred to the authors after reading the paper by Girschik et al.[13] entitled ‘Could mining be protective against prostate cancer?’ Differential risks, i.e., for the relationship between decreasing prostate cancer mortality risk and increasing number of days worked underground, could not be reported in Girschik et al. 2010[13] because all but one of the studies reviewed did not report on working periods underground vs. above ground. Since data on the number of shifts worked underground was available for the Wismut cohort, it was decided to investigate prostate cancer mortality with respect to this variable for the second follow-up (1970-2003), based on 263 prostate cancer deaths and 1.42 million person years. The first indications were (see Figure 1) that the prostate cancer death rates were lower than expected from external comparison rates for the former German Democratic Republic. On performing a full quantitative analysis with sophisticated Poisson regression tools, a model for the differential effect of decreasing prostate cancer mortality risk with increasing number of days worked underground was presented.
Data for an extended Wismut cohort follow-up to the end of 2008 are currently being prepared, and the first indications are that approximately 100 new deaths from prostate cancer will be added to the cohort data with the new follow-up. Once the new data are fully checked and validated, our group intends to extend the analysis in Walsh, et al.[2] by fitting the same types of models to the extended follow-up data and report the results in 2013. It will be interesting to see if the future analyses with the extended follow-up either confirms, weakens, or strengthens the differential and possibly protective effects of working underground on the prostate cancer mortality risk. Particularly so, because there are often reports (see Reiter et al. 2011, for a review)[14] of increased cancer risks for persons working with “light-at-night shifts” (e.g., for breast and prostate cancer, where the evidence supporting this link is the strongest) and the type of analysis presented in Walsh et al. 2012[2] represents the other end of the epidemiological scale in this respect with “not very much light for all shifts.”
If this commentary has piqued curiosity or ideas in other scientists, they should please note that the Wismut epidemiological data can be made available through an application procedure to the German Federal Office of Radiation Protection (BfS) (please see the BfS website at: http://www.bfs.de/en/bfs/forschung/Wismut/Wismut_cohort_proposals.html).
Figure 1: The left-hand ordinate shows the external rates for the former German Democratic Republic (GDR) as normalised by age and calendar year to the internal cohort baseline rates for the number of prostate cancer deaths per 100 000 persons. The right-hand ordinate shows the categorical Standardised Mortality Ration (SMR, which is in unity if the two rates agree), all as a function of age-attained category.
References:
- Kreuzer M, Schnelzer M, Tschense A, et al. Cohort profile: The German uranium miners cohort study (WISMUT cohort), 1946-2003. Int. J. Epidemiol. 2010; 39(4): 980-987.
- Walsh L, Dufey F, Tschense A, et al. Prostate cancer mortality risk in relation to working underground in the Wismut cohort of German uranium miners (1970–2003). BMJ open, 2012;2:e001002. Doi: 10.1136/bmjopen-2012-001002, 2012
- Grosche B, Kreuzer M, Kreisheimer M, et al. Lung cancer risk among German male uranium miners: a cohort study, 1946-1998. Br J Cancer 2006; 95: 1280-1287.
- Walsh L, Tschense A, Schnelzer M, et al. The influence of radon exposure on lung cancer mortality in German uranium miners, 1946–2003. Radiat Res 2010a;173:79-90.
- Schnelzer M, Hammer GP, Kreuzer M, et al. Accounting for smoking in the radon-related lung cancer risk among German uranium miners: results of a nested case-control study. Health Phys 2010;98:20-8.
- Walsh L, Dufey F, Möhner M, et al. Differences in baseline lung cancer mortality between the German uranium miners cohort and the population of the former German Democratic Republic (1960-2003). Radiat. Env. Biophys, 2011;50:57-66.
- Sogl M, Taeger D, Pallapies D et al. Quantitative relationship between silica exposure and lung cancer mortality in German Uranium miners, 1946-2008, Br J Cancer accepted July 2012
- Kreuzer M, Walsh L, Schnelzer M, et al. Radon and risk of extra-pulmonary cancers - Results of the German uranium miners cohort study, 1960–2003. Br J Cancer 2008;99:1946-53.
- Kreuzer M, Grosche B, Schnelzer M, et al. Radon and risk of death from cancer and cardiovascular diseases in the German uranium miners cohort study: follow-up 1946–2003. Radiat Environ Biophys 2010;49:177-185.
- Walsh L, Dufey F, Tschense A, et al. Radon and the risk of cancer mortality – Internal Poisson models for the German uranium miners cohort. Health Phys, 2010b;99:292-300.
- Kreuzer M, Kreisheimer M, Kandel et al. Mortality from cardiovascular diseases in the German uranium miners cohort study, 1946-1998. Radiat. Env. Biophys. 2006;45: 159-166.
- Dufey F, Walsh L, Tschense A, et al. Occupational doses of ionizing iadiation and leukemia mortality. Health Phys 2011;100:548-550.
- Girschik J, Glass D, Ambrosini GL, et al. Could mining be protective against prostate cancer? A study and literature review. Occup Environ Med. 2010;67:365-374.
- Reiter RJ, Tan DX, Sanchez-Barcelo E et al. Circadian mechanisms in the regulation of melatonin synthesis: disruption with light at night and the pathophysiological consequences. Journal of Experimental and Integrative Medicine 2011; 1(1):13-22
Written by:
Linda Walsh, Florian Dufey, and Michaela Kreuzer as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
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