Mayak worker cohort: Characteristics and key results of epidemiological studies

Introduction. The medical registry of workers at the Mayak Production Association (PA) was initially established with the purpose of studying the long-term stochastic health effects of occupational radiation exposure at the first nuclear industry enterprise in the USSR.

Objective. Assessment of radiogenic risk from prolonged occupational exposure among the Mayak PA worker cohort, including the subcohort of workers exposed to normal radiation conditions.

Materials and methods. This study represents one phase of a lifelong retrospective epidemiological investigation of health indicators, including the incidence and mortality from malignant neoplasms (MN), conducted within the framework of the medical-dosimetric registry of Mayak PA workers. The available study cohort is limited to employees of three main production facilities and two auxiliary plants, hired between 1948 and 1982. Within the study cohort, two subcohorts are distinguished based on factual data on radiation exposure levels and assessed medical outcomes. These include the subcohort of 1948–1958, personnel hired during the technology development phase and characterized by high occupational radiation exposure levels and that of 1959–1982, hired during routine operational periods with radiation doses comparable to modern limits. At the current stage, the attained age of workers in the second subcohort and the volume of accumulated data have enabled an analysis focused on individuals having worked under standard conditions, excluding the effects of high doses and dose rates. This has expanded the scope of statistically significant direct estimates of radiogenic MN risk. All studies of radiogenic risk in the cohort of Mayak PA workers were conducted using the Epicure statistical software package.

Results. The cohort comprised 25,755 workers. The vital status during the period of up to 31.12.2018 was known for 94% of subjects. In the 1948–1958 subcohort, the mean cumulative gamma radiation dose was 748 mGy, compared to 130 mGy in the 1959–1982 subcohort. Overall, 10,304 individuals (40.1% of the cohort) received low doses of gamma radiation. The mean cumulative lung dose from alpha radiation due to incorporated ²³⁹Pu was 179.4 mGy, with 329.2 mGy and 41.0 mGy for the 1948–1958 and 1959–1982 subcohorts, respectively. The estimated excess relative risk per 1 Gy of alpha radiation lung dose was 3.5–8 for 60-year-old males. No deviations from linearity were found. Radiogenic risk decreased with an increase in age. A nonlinear dose-response relationship was identified for liver MN. The primary long-term effect of external gamma radiation was leukemia development, where a nonlinear model incorporating effect modification by age at exposure, time since exposure, and attained age provided better approximation than a linear model. For solid MN, the risk coefficient from external gamma radiation ranged 0.1–0.4 per 1 Gy. Among workers employed under normal radiation conditions (1959–1982 hiring period), the attributable risk assessment suggests that 1–5% of MN (excluding tumors in plutonium primary deposition organs) were radiation-induced, solely due to external gamma exposure.

Conclusions. The Mayak PA worker cohort, with its high-quality medical and dosimetric data, serves as a crucial source for direct epidemiological assessments of radiogenic risks from prolonged occupational radiation exposure. The identification of the routine production operation period not only validates the magnitude of carcinogenic risk but also highlights the need to extend both the follow-up period and the cohort itself to include more workers exposed to conditions comparable to modern standards.

1. Panfilov AP. Evolution of the system supporting radiation safety in nuclear industry of Russia and its current status. Radiation and Risk. 2016;25(1):47–64 (In Russ.). EDN: VZDXED

2. Grant EJ, Brenner A, Sugiyama H, Sakata R, Sadakane A, Utada M, et al. Solid Cancer Incidence among the Life Span Study of Atomic Bomb Survivors: 1958–2009. Radiation Research. 2017;187(5):513–37. https://doi.org/10.1667/RR14492.1

3. Sokolnikov ME, Kabirova NR, Okatenko PV, Koshurnikova NA, Tsareva YuV, Martinenko IA, et al. Medical-dosimetry registry of the personnel of “Mayak production association”: status and perspectives. Journal of Radiation Sahety Issues. 2023;3(111):42–55 (In Russ.). EDN: WWGSJD

4. Boice JD, Cohen SS, Mumma MT, Ellis ED. The Million Person Study, whence it came and why. International Journal of Radiation Biology. 2022;98(4):537–50. https://doi.org/10.1080/09553002.2019.1589015

5. Hunter N, Haylock RGE, Gillies M, Zhang W. Extended analysis of solid cancer incidence among the Nuclear Industry Workers in the UK: 1955–2011. Radiation Research. 2022;198(1):1–17. https://doi.org/10.1667/RADE-20-00269.1

6. Richardson DB, Leuraud K, Laurier D, Gillies M, Haylock R, Kelly-Reif K, et al. Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study. BMJ. 2023;16(382):e074520. https://doi.org/10.1136/bmj-2022-074520

7. Koshurnikova NA, Shilnikova NS, Okatenko PV, Kreslov VV, Bolotnikova MG, Sokolnikov ME, et al. Characteristics of the cohort of workers at the Mayak nuclear complex. Radiation Research. 1999;152(4):352–63. https://doi.org/10.2307/3580220

8. Koshurnikova NA, Shilnikova NS, Sokolnikov ME, Bolotnikova MG, Okatenko PV, Vasilenko EK, et al. Medicaldosimetry registry of workers at the “Mayak” production association. International Joural of Low Radiation. 2006;2(3/4):236. https://doi.org/10.1504/IJLR.2006.009516

9. Onischenko GG, Romanovich IK, Istorik OA, Vodovatov AV, Biblin AM, Kormanovskaya TA, et al. On the 125th anniversary of the discovery of radioactivity: history of development and current state of regulation of the provision of the radiation safety of the public. Radiation Hygiene. 2021;14(4):6–16 (In Russ.). https://doi.org/10.21514/1998-426X-2021-14-4-6-16

10. Koshurnikova NA, Shilnikova NS, Okatenko PV, Kreslov VV, Bolotnikova MG, Sokolnikov ME, et al. Characteristics of the cohort of workers of the nuclear enterprise “Mayak PA” (Part I). Radiation Safety Problems. 1998;2:46–55 (In Russ.). EDN: WBJZRP

11. Koshurnikova NA, Shilnikova NS, Okatenko PV, Kreslov VV, Bolotnikova MG, Sokolnikov ME, et al. Characteristics of the cohort of workers of the nuclear enterprise “Mayak PA” (Part II). Radiation Safety Problems. 1998;3:48–58 (In Russ.). EDN: WBJZRP

12. Koshurnikova NA, Okatenko PV, Shilnikova NS, Kuznetsova IS, Sokolnikov ME. Health effects of occupational radiation exposure (cancer mortality among exployees of the main plants of the Mayak production association). Extreme Medicine. 2006;2(16):5–14 (In Russ.). EDN: WLKKQZ

13. Nikipelov BV, Lyzlov AF, Koshurnikova NA. Experience of the first nuclear industry enterprise (levels of radiation and health of personnel). Priroda. 1990;2:30–8 (In Russ.). EDN: WBJMEB

14. Vasilenko EK. Dosimetry of external irradiation of manufacturers of PA Mayak: devices, methods, and monitoring results. In: Kiselev MF, Romanov SA, ed. Sources and effects of irradiation of manufacturers of PA “Mayak” and the population located on the territory of the industrial enterprise. Ozyorsk; 2009:66–135 (In Russ.). EDN: ZBOYBT

15. Napier BA. The Mayak worker dosimetry system (MWDS-2013): an introduction to the documentation. Radiation Protection Dosimetry. 2017;176(1–2):6–9. https://doi.org/10.1093/rpd/ncx020

16. Hohrjakov VF, Hohrjakov VV, Suslova KG, Vostrotin VV, Shhadilov AE, Sokolova AB, et al. Progress in plutonium dosimetry development at Mayak PA. Radiation Safety Problems. 2006;41(1):59–80 (In Russ.). EDN: JUURIP

17. Efimov AV, Sokolova AB. History and program of biophysical examinations in the epidemiological cohort of employees of the PA “Mayak”. Radiation and Risk. 2024;33(4):131–43 (In Russ.). https://doi.org/10.21870/0131-3878-2024-33-4-131-143

18. Khokhryakov VV, Khokhryakov VF, Suslova KG, Vostrotin VV, VVedensky VE, Sokolova AB, et al. Mayak Worker Dosimetry System 2008 (MWDS-2008): Assessment of Internal Dose from Measurement Results of Plutonium Activity in Urine. Health Physics. 2013;104(4):366–78. https://doi.org/10.1097/HP.0b013e31827dbf60

19. Birchall A, Vostrotin VV, Puncher M, Efimov AV, Dorrian M-D, Soolova AB, et al. The Mayak worker dosimetry system (MWDS-2013) for internally deposited plutonium: an overview. Radiation Protection Dosimetry. 2017;176(1–2):10–31. https://doi.org/10.1093/rpd/ncx014

20. Vostrotin VV, Napier BA, Zhdanov AV, Miller S, Sokolova AB, Bull RK, et al. The Mayak worker dosimetry system (MWDS-2016): internal dosimetry results and comparison with MWDS-2013. Radiation Protection Dosimetry. 2019;184(2):201–10. https://doi.org/10.1093/rpd/ncy200

21. Sokolnikov ME, Gilbert ES, Preston DL, Ron E, Shilnikova NS, Koshurnikova NA, et al. Lung, liver and bone cancer mortality in Mayak workers. International Journal of Cancer. 2008;123(4):905–11. https://doi.org/10.1002/ijc.23581

22. Gilbert ES, Sokolnikov ME, Preston DL, Schonfeld SJ, Schadilov AE, Vasilenko EK, et al. Lung Cancer Risks from Plutonium: An Updated Analysis of Data from the Mayak Worker Cohort. Radiation Research. 2013;179(3):332–42. https://doi.org/10.1667/RR3054.1

23. Labutina EV, Kuznetsova IS, Hunter N, Harrison J, Koshurnikova NA. Radiation Risk of Malignant Neoplasms in Organs of Main Deposition for Plutonium in the Cohort of Mayak Workers with Regard to Histological Types. Health Physics. 2013;105(2):165–76. https://doi.org/10.1097/HP.0b013e31828f57df

24. Shilnikova NS, Preston DL, Ron E, Gilbert ES, Vassilenko EK, Koshurnikova NA, et al. Cancer Mortality Risk among Workers at the Mayak Nuclear Complex. Radiation Research. 2003;159(6):787–98. https://doi.org/10.1667/0033-7587(2003)159

25. Kuznetsova IS, Labutina EV, Hunter N. Radiation Risks of Leukemia, Lymphoma and Multiple Myeloma Incidence in the Mayak Cohort: 1948–2004. PLoS ONE. 2016;11(9):e0162710. https://doi.org/10.1371/journal.pone.0162710

26. Sokolnikov ME, Preston DL, Stram D, Martinenko IA, Koshurnikova NA. Chronic effect of ionizing radiation and leukomogenic risk. Chronic radiation exposure: late medical and biological effects. Proceedings of the 7 th scientific conference. Chelyabinsk; 2022 (In Russ.).

27. Sokolnikov M, Preston D, Stram DO. Mortality from solid cancers other than lung, liver, and bone in relation to external dose among plutonium and non-plutonium workers in the Mayak Worker Cohort. Radiation and Environmental Biophysics. 2017;56(1):121–5. https://doi.org/10.1007/s00411-016-0670-5

28. Sokolnikov ME, Preston DL, Gilbert E, Schonfeld S, Koshurnikova NA. Radiation Effects on Mortality from Solid Cancers Other than Lung, Liver, and Bone Cancer in the Mayak Worker Cohort: 1948–2008. PLoS ONE. 2015;10(2):e0117784. https://doi.org/10.1371/journal.pone.0117784

29. Hunter N, Kuznetsova IS, Labutina EV, Harrison JD. Solid cancer incidence other than lung, liver and bone in Mayak workers: 1948–2004. British Journal of Cancer. 2013;109(7):1989–96. https://doi.org/10.1038/bjc.2013.543

30. Wakeford R. What about the workers? Journal of Radiology Protection. 2024;44(2):011504. https://doi.org/10.1088/1361-6498/ad4eea

31. Laurent O, Samson E, Caer-Lorho S, Fournier L, Laurier D, Leuraud K. Updated mortality analysis of SELTINE, the French cohort of nuclear workers, 1968–2014. Cancers. 2022;15(1):79. https://doi.org/10.3390/cancers15010079

32. Haylock RGE, Gillies M, Hunter N, Zhang W, Phillipson M. Cancer mortality and incidence following external occupational radiation exposure: an update of the 3rd analysis of the UK National Registry for Radiation Workers. British Journal of Cancer. 2018;119(5):631–7. https://doi.org/10.1038/s41416-018-0184-9

33. Hunter N, Haylock R. Extended analysis of solid cancer incidence among nuclear industry workers in the UK 1955–2011: comparison of workers first hired in earlier and later periods. Journal of Radiology Protection. 2024;44(2):021515. https://doi.org/10.1088/1361-6498/ad4c72

34. Kelly-Reif K, Bertke SJ, Daniels RD, Richardson DB, Schubauer-Berigan MK. Ionizing radiation and solid cancer mortality among US nuclear facility workers. International Journal of Epidemiology. 2023;52(4):1015–24. https://doi.org/10.1093/ije/dyad075

35. Richardson DB, Daniels RD, Hamra GB, Leuraud K, Thierry-Chef I. Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS). BMJ. 2015;351:h535. https://doi.org/10.1136/bmj.h5359

36. Wakeford R. Overview of epidemiological studies of nuclear workers: opportunities, expectations, and limitations. Journal of Radiological Protection. 2021;41(4):1075. https://doi.org/10.1088/1361-6498/ac0df4

37. Cardis E, Vrijheid M, Blettner M, Gilbert E, Hakama M, Hill G, et al. The 15-country collaborative study of cancer risk among radiation workers in the nuclear industry: estimates of radiation-related cancer risks. Radiation Research. 2007;167(4):396–416. https://doi.org/10.1667/RR0553.1

38. Wakeford R. Solid cancer mortality among US radiation workers. International Journal of Epidemiology. 2023;52(6):1992–4. https://doi.org/10.1093/ije/dyad131

39. Schubauer-Berigan MK, Daniels RD, Bertke SJ, Tseng C-Y, Richardson DB. Cancer mortality through 2005 among a pooled cohort of U.S. nuclear workers exposed to external ionizing radiation. Radiation Research. 2015;183(6):620–31. https://doi.org/10.1667/RR13988.1

40. Kuznetsova IS. Comparison of Radiation Risk of Cancer Incidence among PA Mayak Workers Hired at Different Calendar Periods. Medical Radiology and Radiation Safety. 2021;66(6):50–6 (In Russ.). https://doi.org/10.12737/1024-6177-2021-66-6-50-56

41. Kuznetsova IS. Radiation risk of mortality from malignant neoplasms among workers hired at different periods of Mayak PA activity. Radiation Safety Problems. 2023;4(112):82–9 (In Russ.). EDN: ZMZQJW