Effect of follow-up period on minimal significant dose level and radiation risk estimate in the cohort of Chernobyl liquidators

"Radiation and Risk", 2018, vol. 27, No. 3, pp.32-41

DOI: 10.21870/0131-3878-2018-27-3-32-41


Ivanov V.K. – Deputy Director, Chairman of RSCRP, Corresponding Member of RAS. A. Tsyb MRRC, Obninsk.
Karpenko S.V. – Engineer. A. Tsyb MRRC, Obninsk. Contacts: 4 Korolev str., Obninsk, Kaluga region, Russia, 249036. Tel.: (484) 399-32-81; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. .
Kashcheev V.V. – Head of Lab., C. Sc., Biol. A. Tsyb MRRC, Obninsk.
Lovachev S.S. – Research Assistant. A. Tsyb MRRC, Obninsk.
Kashcheeva P.V. – Senior Researcher, C. Sc., Biol. A. Tsyb MRRC, Obninsk.
Shchukina N.V. – Senior Re-searcher; Tumanov K.А. – Head of Lab., C. Sc., Biol. A. Tsyb MRRC, Obninsk.
Kochergina E.V. – Head of Lab., C. Sc., Med. A. Tsyb MRRC, Obninsk.
Maksioutov M.A. – Head of Dep., C. Sc., Tech. A. Tsyb MRRC, Obninsk.


The article presents results of estimating the lowest dose level in the cohort of Russian Chernobyl liquidators at which excess relative radiation risk is a significant value. The liquidators were selected in accordance with developed criteria, all of enrolled people had officially certified individual doses of whole-body gamma-radiation. The average age of the liquidators at the time of entry into the exclusion (accident) zone was 33.5 years. The average dose of external whole-body gamma-radiation exposure, that liquidators received for the period of their work within the accident zone, was 132.7 mGy. For the follow-up period lasted from 1992 over 2016, 6530 primary solid cancer cases were diagnosed. The 24-year follow-up period was divided into three shorter follow-up peri-ods: 1992-2009, 1992-2013 and 1992-2016 years. For each follow-up period a minimal dose level (p<0.05) with statistically significant linear dose-solid cancer incidence relationship was calculated. With solid cancer incidence estimates of minimal radiation dose declined with longer follow-up time-period: Dmin was 0.25 Gy for 1992-2009; 0.175 Gy for 1992-2013 and 1992-2016 years. Estimated ERR per Gy tended to be higher with longer follow-up: ERR/1Gy=0.56 (95% CI: 0.09, 1.09) for the follow-up period 1992-2009, observation period 1992-2013, ERR/1Gy=0.96 (95% CI: 0.13, 1.90 for 1992-2013 and ERR/1Gy=0.95 (95% CI: 0.19, 1.80) for 1992-2016. Thus, it is revealed that the minimum dose level decreases with an increase of the period of observation of the cohort.

Key words
Cohort studies, solid cancer incidence, cohort of male liquidators, follow-up period, excess relative risk, radiation risk, dose of radiation.


1. ICRP, 2007. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103.Ann. ICRP 37(2-4).

2. Norms of radiation safety (NRS-99/2009) Sanitary rules and regulations. SanPiN Moscow, Federal Center for Hygiene and Epidemiology of Rospotrebnadzor, 2009. 100 p. (In Russian).

3. Little M.P., Muirhead C.R. Evidence for curvilinearity in the cancer incidence dose-response in the Japanese atomic bomb survivors. Int. J. Radiat. Biol., 1996, vol. 70, no. 1, pp. 83-94.

4. Little M.P., Muirhead C.R. Curvilinearity in the dose-response curve for cancer in Japanese atomic bomb survivors. Environ. Health Perspect., 1997, vol. 105, suppl. 6, pp. 1505-1509.

5. Little M.P., Muirhead C.R. Curvature in the cancer mortality dose response in Japanese atomic bomb sur-vivors: absence of evidence of threshold. Int. J. Radiat. Biol., 1998, vol. 74, no. 4, pp. 471-480.

6. Cologne J., Preston D.L., Grant E.J., Cullings H.M., Ozasa K. Effect of follow-up period on minimal-significant dose in the atomic bomb survivir studies. Radiat. Eviron. Biophys., 2017, vol. 57, no. 1, pp. 83-88.

7. Ozasa K., Shimizu Y., Suyama A., Kasagi F., Soda M., Grant E.J., Sakata R., Sugiyama H., Kodama K. Studies of the mortality of atomic bomb survivors, Report 14, 1950-2003: an overview of cancer and noncancer diseases. Radiat. Res., 2012, vol. 177, no. 3, pp. 229-243.

8. Grant E.J., Brenner A., Sugiyama H., Sakata R., Sadakane A., Utada M., Cahoon E.K., Milder C.M., Soda M., Cullings H.M., Preston D.L., Mabuchi K., Ozasa K. Solid cancer incidence among the Life Span Study of atomic bomb survivors: 1958-2009. Radiat. Res., 2017, vol. 187, no. 5, pp. 513-537.

9. Ivanov V.K., Rastopchin E.M., Gorsky A.I., Ryvkin V.B. Cancer incidence among liquidators of the Chernobyl accident: solid tumors, 1986-1995. Health Phys., 1998, vol. 74, no. 3, pp. 309-315.

10. Ivanov V.K., Gorski A.I., Maksioutov M.A., Tsyb A.F., Souchkevitch G.N. Mortality among the Chernobyl emergency workers: estimation of radiation risks (preliminary analysis). Health Phys., 2001, vol. 81, no. 5, pp. 514-521.

11. Kesminiene A., Cardis E., Tenet V., Ivanov V.K., Kurtinaitis J., Malakhova I., Stengrevics A., Tekkel M. Studies of cancer risk among Chernobyl liquidators: materials and methods. J. Radiol. Prot., 2002, vol. 22, no. 3A:A137-141.

12. Ivanov V.K., Gorski A.I., Tsyb A.F., Ivanov S.I., Naumenko R.N., Ivanova L.V. Solid cancer incidence among the Chernobyl emergency workers residing in Russia: estimation of radiation risks. Radiat. Environ. Biophys., 2004, vol. 43, no. 1, pp. 35-42.

13. Ivanov V.K. Late cancer and noncancer risks among Chernobyl emergency workers of Russia. Health Phys., 2007, vol. 93, no. 5, pp. 470-479.

14. Ivanov V.K., Gorsky A.I., Kashcheev V.V., Maksioutov M.A., Tumanov K.A. Latent period in induction of radiogenic solid tumors in the cohort of emergency workers. Radiat. Environ. Biophys., 2009, vol. 48, no. 3, pp. 247-252.

15. Ivanov V.K., Tsyb A.F., Khait S.E., Kashcheev V.V., Chekin S.Yu., Maksioutov M.A., Tumanov K.A. Leukemia incedence in the Russian cohort of Chernobyl emergency workers. Radiat. Environ. Biophys., 2012, vol. 51, no. 2, pp. 143-149.

16. Breslow N., Day N. Statistical methods in cancer research. Volume II. The disign and analysis of cohort studies. Scientific publication 82. International Agency for Research on Cancer, 1987. 406 p.

17. Walsh L., Schneider U. The influence of follow-up on DS02 low-dose ranges with a significant excess relative risk of all solid cancer in the Japanese A-bomb survivors. Radiat. Eviron. Biophys., 2016, vol. 55, no. 4, pp. 509-515.

18. Kashcheev V.V., Chekin S.Yu., Maksiutov M.A., Tumanov K.A., Kochergina E.V., Kashcheeva P.V., Shchukina N.V. Incidence and mortality of solid cancer among emergency workers of the Chernobyl accident: assessment of radiation risks for the follow-up of 1992-2009. Radiat. Eviron. Biophys., 2015, vol. 54, no. 1, pp. 13-23.

19. Ivanov V.K., Tsyb A.F., Gorsky A.I., Maksyutov M.A., Rastopchin E.M., Konogorov A.P., Korelo A.M., Biryukov A.P., Matyash V.A. Leukaemia and thyroid cancer in emergency workers of the Chernobyl accident: estimation of radiation risks (1986-1995). Radiat. Environ. Biophys., 1997, vol. 36, no. 1, pp. 9-16.

20. Ivanov V.K., Tsyb A.F., Gorsky A.I., Maksyutov M.A., Rastopchin E.M., Konogorov A.P., Biryukov A.P., Matyash V.A., Mould R.F. Thyroid cancer among "liquidators" of the Chernobyl accident. Br. J. Radiol., 1997, vol. 70, no. 837, pp. 937-941.

21. Ivanov V.K., Tsyb A.F., Petrov A.V., Maksioutov M.A., Shilyaeva T.P., Kochergina E.V. Thyroid cancer incidence among liquidators of the Chernobyl accident: absence of dependence of radiation risks on external radiation dose. Radiat. Environ. Biophys., 2002, vol. 41, no. 3, pp. 195-198.

22. Ivanov V.K., Gorski A.I., Maksioutov M.A., Vlasov O.K., Godko A.M., Tsyb A.F., Tirmarche M., Valenty M., Verger P. Thyroid cancer incidence among adolescents and adults in the Bryansk region of Russia following the Chernobyl accident. Health Phys., 2003, vol. 84, no. 1, pp. 46-60.

23. Ivanov V.K., Chekin S.Y., Kashcheev V.V., Maksioutov M.A., Tumanov K.A. Risk of thyroid cancer among Chernobyl emergency workers of Russia. Radiat. Environ. Biophys., 2008, vol. 47, no. 4, pp. 463-467.

24. Ivanov V.K., Kashcheev V.V., Chekin S.Y., Maksioutov M.A., Tumanov K.A, Vlasov O.K., Shchukina N.V., Tsyb A.F. Radiation-epidemiological studies of thyroid cancer incidence in Russia after the Chernobyl accident (estimation of radiation risks, 1991-2008 follow-up period). Radiat. Prot. Dosimetry, 2012, vol. 151, no. 3, pp. 489-499.

25. Preston D.L., Lubin J.H., Pierce D.A. EPICURE User's Guide. Seattle, Hirosoft International Corp., 1993.

26. Preston D.L., Lubin J.H., Pierce D.A. EPICURE Command Summary. Seattle, Hirosoft International Corp., 1993.

Full-text article (in Russian)