Cancer Risk Due to Radiation Exposure in the Southern Urals ...
Cancer Risk Due to Radiation Exposure in the Southern Urals Mayak Workers and Techa River Cohort Studies Daniel Stram; University of Southern California Plenary Session #3 Monday - October 1, 2018 Outline Epidemiologic Studies Mayak Workers Cohort (MWC) Techa River Cohort (TRC) Eastern European Radioactive Trace Cohort (EURTC) A little statistics Risk results from these cohorts 2
Mayak Production Association Nuclear facilities located in the southern Urals where the plutonium for the first Soviet nuclear weapons were produced Construction began in November 1945 First bomb test August 1949 3 Occupational exposures: Included internal (Pu) and external (gamma) radiation Mean cumulative occupational
exposures were high Exposures were protracted over (often many) years 4 Environmental Exposures Source: Releases from Mayak PA into Techa River in 1949-1956. About 1017 Bq radiation East Urals Radioactive Trace (EURT, 29 Sept 1957) Thermal explosion of storage tank 7x1016 Bq radioactivity released 5
Map of regions of contamination v\ 6 The three studies of interest here 1. Mayak Workers Cohort (MWC) study 2. Mayak workers hired from 1948-1982 (n=26,000)
MWDS dosimetry based on film badges from early on. Plutonium monitoring began in 1970s. Follow-up from 1948 current Techa River Cohort (TRC) study Persons (n=30,000) born before 1 Jan 1950 who resided in one or more of the 41 Techa riverside villages between 1950 and 1960 TRDS dosimetry 3.
Internal dose estimates based on many individual measurements. External dose estimates from measured and calculated dose rate in air. Follow-up from 1950-current East European Radioactive Trace (EURTC) cohort study Cohort definition: Persons (n=22,000) residing in one or more of 33 EURT villages in Chelyabinsk oblast between 29 Sept 1957 and 1960 Dosimetry same as TRDS Follow-up from 29 Sept 1957 - current 7 Selected Publications
MWC Mortality from lung, liver, bone 1948-2003 Mortality from lung cancer, with follow-up through 2008 Mortality from solid cancers other than lung, liver, and bone 1948-2008 Leukemia in the MWC 1948-2008*(in review) Most used MWDS2008 TRC Solid cancer mortality, 1950-2007 Solid cancer incidence, 1956-2007 Leukemia incidence, 1953-2007 All studies used TRDS 2009 8 Recent progress: Techa River Cohort Extension to include EURTC in risk
analyses Follow-up through 2016. Dosimetry updates (TRDS2016) Includes estimation of doses from EURT exposures Utilizes updated source term, river transport models, increased individualization of doses. Represents dosimetric uncertainty using Monte-Carlo realizations of possible annual dose 9 Recent progress in MWC Update of follow-up through 2015 Improved dose estimates in MWDS2016 Changes in biological/chemical parameters
lead to generally higher Pu dose Provides MC realizations representing uncertainty for both plutonium doses and occupational gamma exposures 10 Mean MWDS 2016 vs 2008 Pu dose Progress in statistical modeling Incorporation of dosimetric uncertainty into epidemiologic calculations IE what do we do with the multiple realizations??
12 Dose uncertainty as represented by MC realizations of internal dose (cumulative Mayak Lung Dose) Units are Gy 13 Dose uncertainty as incorporated into the epidemiologic analysis: adjusted and unadjusted confidence bounds Uses corrected information (CIM) approach of Stram et al 2015 and Zhang et al 2017 14
Lung cancer in MWC associated with Gilbert 2013: MWDS 2008 follow-up through 2008, no dose uncertainty ERR / Gy at age 60 (Wald Confidence Interval) 56) Males Females 7.4 24 (5.0 11) (11 Stram et al, (in progress) MWDS 2016, follow-up through 2014, including adjustment for uncertainty Males
Females ERR / Gy at age 60 (Wald CI) (Adjusted CI) 3.6 (2.4 4.8) (1.6 8.8) 9.9 (4.2 15.7) (3.3 29) 15 Dose response over 0-4 Gy Pu exposure 0
1 2 Pu lung dose (Gy) 3 4 16 Dose response over 0-0.5 Gy Pu exposure 0 .1
.2 .3 Pu lung dose (Gy) .4 .5 17 Lung cancer associated with MWC external dose Sokolnikov 2008: MWDS 2008 follow-up through 2003, no dose uncertainty Males+Females ERR / Gy at age 60 0.19
(Confidence Interval) (0.050.39) Stram et al, (in progress) follow-up through 2014 Males+ Females ERR / Gy at age 60 0.20 (Unadjusted Wald CI) (0.07 0.32) (Adjusted Wald CI) (0.07 0.34) 18 External lung dose response 0-2.5 Gy .6
22 Adjusted for Non-CLL leukemia in the TRC Krestinina 2013: Mortality TRDS 2009 follow-up through 2007, no dose uncertainty TRC only ERR / Gy 2.2 (Likelihood-based Confidence Interval) (0.85.4) Current analyses: Mortality follow-up through 2016, includes adjustment for uncertainty, TRDS16 TRC+EURT
ERR / Gy (Likelihood-based CI) (Wald based CI) Adjusted Wald-based CI 2.04 (0.75 4.4) (0.33 3.5) (0.20 -- 45.0) 23 Non-CLL leukemia mortality in the MWC (Sokolnikov 2018 in review) gamma dose-response appears to be quadratic in RBM exposure Attained age rapidly reduces excess
relative risk of exposure proportional to 1/age2.5 The ERR for doses received 2-4 years in the past is roughly 3 times that for doses received 5+ years prior No evidence of effect of Pu on leukemia risk 24 For example 60 year old last exposed before age 55 the ERR for a 1 Gy total dose is
0.25. For 100 mGy exposure this becomes 0.0025 At age 70 these ERRs are reduced by approximately 1/3. The significance of this description is driven by the higher exposures Uncertainty calculations in progress25 Conclusions These studies provide compelling evidence for radiation effects (Lung, Solid Cancers, Leukemia) due to protracted exposures to both internal and external radiation The information for more detailed site-specific analyses is limited. Most site-specific risk estimates tend to be positive, but with
limited power Both studies are providing information but about different ranges of dose. Techa doses are lower but risk estimates / Gy are higher Techa doses are providing information about low doses delivered at very low rates. Techa is relevant to accident, terrorist scenarios Uncertainty results reflect that internal exposures (to alpha from Pu, beta from Sr), are inherently harder to estimate than external dose.
26 Acknowledgments Funding by the US Department of Energy, Russian Health Studies Program, and by the Russian Federal Medical and Biological Agency DOE Program Officer Barrett Fountos Key co-investigators SUBI: Mikhail Sokolnikov URCRM: Ludmilla Krestinina PNNL: Bruce Napier Hirosoft: Dale Preston 27
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