We investigated monthly perinatal mortality in Japan for the years 2001 to 2014 with emphasis on detrimental pregnancy outcome possibly caused by the earthquake, the tsunami, or the subsequent Fukushima nuclear disaster in March 2011. In the 2 severely contaminated prefectures Iwate and Miyagi that were also heavily hit by the tsunami, there was a more than 50% increase in perinatal mortality in March and April 2011, and there was essentially no increase in the remainder of the year 2011. By contrast, looking at the 4 other severely radioactively affected prefectures (Fukushima, Ibaraki, Tochigi, and Gunma), which remained nearly untroubled after the natural disasters, we see essentially no increase in the occurrence of PDs in March and April 2011, and this applies to the rest of that year as well. In addition to the short-term effects in March and April 2011 in all those 6 severely radioactively contaminated prefectures, however, we observed distinct long-term increases in perinatal mortality of approximately 15% from January 2012 onward. Furthermore, in the 3 moderately exposed prefectures Chiba, Saitama, and Tokyo there is a long-term relative 6.8% increase in perinatal mortality after January 2012, and there is apparently no impact on perinatal mortality in Japan excluding the severely and moderately affected prefectures, neither by the earthquake and the tsunami nor by the Fukushima accident.
Although the present study is of an ecological type based on highly aggregated data that cannot prove causality in principle, it nevertheless provides some evidence of causality according to the well-known Bradford-Hill criteria: temporality and biologic gradient. The observed effects occur 10 months after the possible cause (ionizing radiation). This suggests impact primarily on ovum and sperm and less on the embryo or the fetus. Moreover, the PD increases show a certain dose–response association with the presumable exposure: unaffected as well as moderately and severely impacted prefectures are associated with no, medium, and maximum effects, respectively. The observed optimum overall time-lag of 10 months between the radiological event and the jump in the PD proportion may be explained by the superposition of the periods necessary for the dispersal of the radioactivity (several weeks) and the pregnancy length. Note that the duration of pregnancies at elevated risk of adverse perinatal outcome may be considerably shorter than the usual 9 months.
A major limitation of this study is the highly aggregated nature of the data considered impeding causal inference in principle. The only potential confounding variables controlled for were time (secular trend), seasonality (month-to-month variation), and the tsunami itself. Otherwise, we are not aware of any monthly statistics on a prefecture-by-prefecture basis that reflects possible confounding variables like stresses to pregnant women and any other risk factors for PD that could be linked to the PD occurrence in Japan before and after Fukushima. Ideally, population based data on perinatal risk factors will be generated to complement future investigations. Another problem is whether the displacement of the population during the Tsunami and the nuclear accident might have confounded our results and conclusions. We are again not aware of any data concerning this issue. However, if young parents have been exposed and put at a higher risk for untoward pregnancy outcome prior to displacement, this could have biased our effect estimates downward, as corresponding PDs would have been counted in the “unexposed” prefectures (exposure misclassification).
In view of the detrimental reproductive effects in Europe after Chernobyl, and acknowledging the observed tentative spatiotemporal ecological dose–response association between radiation exposure and perinatal mortality 10 months after Fukushima, we conjecture that the increases of PDs in the radioactively contaminated prefectures in Japan may possibly be due to radioactive releases by the Fukushima nuclear power plant accident. It will be interesting to more precisely monitor the future temporal development of the various reproductive outcome measures in Japan stratified by radiological exposure to weaken or to corroborate our findings and conclusions.
As the Japanese Government plans to let inhabitants return to areas prospectively exposed to radiation by less than 20 mSv/a (milli-Sieverts per year), our findings are relevant for the resettlement of people formerly evacuated from the highly contaminated zone, see http://www.pref.fukushima.lg.jp/site/portal-english/rev-plan-3.html. The “Ottawa Charter of Health Promotion” emphasizes that political responsibility is needed and that global and environmental factors play an important role in the care for public health. To take political responsibility requires full and continuous access to information, learning opportunities in the various environmental health research disciplines, as well as adequate funding support for ecological, environmental, and medical investigations.
The authors thank the Editors of ‘Epidemiology’ and ‘Medicine’ for general support and 6 reviewers for detailed critical and constructive suggestions on earlier drafts. The authors also thank Shinobu Katsuragi for her valuable moderation and translation that supported and greatly facilitated the communication between the Japanese authors and the German author.
2. World Health Organization. 5. Risk characterization. Health Risk, Assessment from the Nuclear Accident
after the 2011 Great East Japan, Earthquake and Tsunami Based on a Preliminary Dose Estimation. Geneva: WHO Press; 2013.
4. Park JS, Kim DW, Chung JW, et al Safety of exposure from extremely low frequency magnetic fields during prenatal ultrasound examinations in clinicians and pregnant women. Medicine (Baltimore)
6. Vogel F, Motulsky AG. Human Genetics. Berlin Heidelberg New York Tokyo: Springer; 1986.
7. Neel JV, Schull WJ. The Effect of Exposure to the Atomic Bombs on Pregnancy Termination in Hiroshima and Nagasaki. In: Council NAoSNR, editor, The Effect of Exposure to the Atomic Bombs on Pregnancy Termination in Hiroshima and Nagasaki. Vol Publ. No. 461. Washington (DC) 1956.
8. Schull WJ, Neel JV. Radiation and the sex ratio in man. Science
9. Scherb H, Voigt K, Kusmierz R. Ionizing radiation
and the human gender proportion at birth – a concise review of the literature and complementary analyses of historical and recent data. Early Hum Dev
10. Grech V. Births and male:female birth ratio in Scandinavia and the United Kingdom after the Windscale fire of October 1957. Int J Risk Saf Med
11. Scherb H, Kusmierz R, Voigt K. Letter to the editor. Int J Risk Saf Med
12. Sever LE, Gilbert ES, Hessol NA, et al A case-control study of congenital malformations and occupational exposure to low-level ionizing radiation
. Am J Epidemiol
13. Parker L, Pearce MS, Dickinson HO, et al Stillbirths among offspring of male radiation workers at Sellafield nuclear reprocessing plant. Lancet
14. Dickinson HO, Parker L, Binks K, et al The sex ratio of children in relation to paternal pre-conceptional radiation dose: a study in Cumbria, northern England. J Epidemiol Community Health
15. Shirangi A, Fritschi L, Holman CD. Maternal occupational exposures and risk of spontaneous abortion in veterinary practice. Occup Environ Med
16. Wiesel A, Spix C, Mergenthaler A, et al Maternal occupational exposure to ionizing radiation
and birth defects. Radiat Environ Biophys
17. Stewart A, Kneale GW. Radiation dose effects in relation to obstetric x-rays and childhood cancers. Lancet
18. Cox DW. An investigation of possible genetic damage in the offspring of women receiving multiple diagnostic pelvic X rays. Am J Hum Genet
19. Goldberg MS, Mayo NE, Levy AR, et al Adverse reproductive outcomes among women exposed to low levels of ionizing radiation
from diagnostic radiography for adolescent idiopathic scoliosis. Epidemiology
20. Winther JF, Boice JD Jr, Thomsen BL, et al Sex ratio among offspring of childhood cancer survivors treated with radiotherapy. Br J Cancer
21. Lazjuk GI, Nikolaev DL, Novikova IV. Changes in registered congenital anomalies in the Republic of Belarus after the Chernobyl accident. Stem Cells
1997; 15 (suppl 2):255–260.
22. Zieglowski V, Hemprich A. Facial cleft birth rate in former East Germany before and after the reactor accident in Chernobyl. Mund Kiefer Gesichtschir
23. Koerblein A, Kuchenhoff H. Perinatal mortality in Germany following the Chernobyl accident. Radiat Environ Biophys
24. Luning G, Scheer J, Schmidt M, et al Early infant mortality in West Germany before and after Chernobyl. Lancet
25. Scherb H, Voigt K. The human sex odds at birth after the atmospheric atomic bomb tests, after Chernobyl, and in the vicinity of nuclear facilities. Environ Sci Pollut Res Int
26. Scherb H, Weigelt E, Brüske-Hohlfeld I. European stillbirth
proportions before and after the Chernobyl accident. Int J Epidemiol
27. Scherb H, Weigelt E, Brüske-Hohlfeld I. Regression analysis of time trends in perinatal mortality in Germany, 1980–1993. Environ Health Perspect
28. Sperling K, Neitzel H, Scherb H. Evidence for an increase in trisomy 21 (Down syndrome) in Europe after the Chernobyl reactor accident. Genet Epidemiol
29. Wertelecki W. Malformations in a Chornobyl-impacted region. Pediatrics
31. Scherb H, Weigelt E. Congenital malformation and stillbirth
in Germany and Europe before and after the Chernobyl nuclear power plant accident. Environ Sci Pollut Res, Special Issue
32. Scherb H, Kusmierz R, Voigt K. Increased sex ratio in Russia and Cuba after Chernobyl: a radiological hypothesis. Environ Health
33. Grosche B, Irl C, Schoetzau A, et al Perinatal mortality in Bavaria, Germany, after the Chernobyl reactor accident. Radiat Environ Biophys
36. Koya PK, Jaikrishan G, Sudheer KR, et al Sex ratio at birth: scenario from normal- and high-level natural radiation areas of Kerala coast in south-west India. Radiat Environ Biophys
37. Scherb H, Grech V, Kusmierz R, et al. Letter to the Editor “Radiation and Environmental Biophysics”: Comment on “Sex ratio at birth: scenario from normal- and high-level natural radiation areas of Kerala coast in south-west India” by Koya PK, Jaikrishan G, Sudheer KR, Andrews VJ, Madhusoodhanan M, Jagadeesan CK, Das B. Radiat Environ Biophys. 2016 Mar;55 (1):3-4. doi: 10.1007/s00411-015-0627-0. Epub 2015 Dec 28.
38. Spycher BD, Lupatsch JE, Zwahlen M, et al Background ionizing radiation
and the risk of childhood cancer: a census-based nationwide cohort study. Environ Health Perspect
39. Sermage-Faure C, Laurier D, Goujon-Bellec S, et al Childhood leukemia around French nuclear power plants – the Geocap study, 2002–2007. Int J Cancer
40. Spix C, Schmiedel S, Kaatsch P, et al Case-control study on childhood cancer in the vicinity of nuclear power plants in Germany 1980–2003. Eur J Cancer
41. Scherb H, Kusmierz R, Voigt K. Human sex ratio at birth and residential proximity to nuclear facilities in France. Reprod Toxicol
42. Scherb H, Kusmierz R, Sigler M, et al Modeling human genetic radiation risks around nuclear facilities in Germany and five neighboring countries: A sex ratio study. Environ Model Software
43. Tsuda T, Tokinobu A, Yamamoto E, et al Thyroid cancer detection by ultrasound among residents ages 18 years and younger in Fukushima, Japan: 2011 to 2014. Epidemiology
44. Suzuki S. Re: thyroid cancer among young people in Fukushima. Epidemiology
47. Rothman KJ, Greenland S. Modern Epidemiology. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 1998.
48. Scherb H, Voigt K. Analytical ecological epidemiology: exposure-response relations in spatially stratified time series. Environmetrics
49. Carlstein E, Müller HG, Siegmund D. Change-Point Problems. Bethesda: Institute of Mathematical Statistics; 1994.
50. Scherb H. Letter to the editor. Int J Risk Saf Med
51. Auvinen A, Vahteristo M, Arvela H, et al Chernobyl fallout and outcome of pregnancy in Finland. Environ Health Perspect
53. Leischik R, Dworrak B, Strauss M, et al Plasticity of health. Ger J Med