Radon and risk: uncertainties of the dose-effect relationship in the low-dose region, the Radon dose coefficients and the limits for Radon in homes

Transcription

1 Zentrum für Strahlenschutz und Radioökologie Institut für Radioökologie und Strahlenschutz Leibniz Universität Hannover Leibniz Universität Hannover Radon and risk: uncertainties of the dose-effect relationship in the low-dose region, the Radon dose coefficients and the limits for Radon in homes Rolf Michel GREWIS-Consortium Annual Meeting 2015, GSI, Content Radon measurement quantities What do we know about the risk? Lung cancer in miners Radon in homes What do we know about the uncertainties? Dose coefficients Epidemiological approach Dosimetric approach Reference values for Radon Individual and collective risks Summary and open questions 1

2 LNT EAR HRTM PAEC BB WLM PAR Rn ERR OR Rn FP Bq h m -3 F ET 1 msv EEC 95% CI AL AMAD f P PAC RR ET 2 WL detriment pci L -1 Bq m -3 bb msv/(bq m -3 ) Measurement quantities for Radon and Radon progeny Working Level (WL) 1 WL = Bq/m 3 EEC = 100 pci l -1 EEC 1 WL is any combination of Rn-222 and its progeny in one liter air which emits a potential -energy of 1, MeV. Working Level Month (WLM) 1 WLM is the exposure in 1 month (170 h) at 1 WL. 1 h Bq m -3 = F WLM F is the equilibrium factor. In homes 0,2 < F < 0,6 applies with a mean of F = 0,4. 2

3 Radon exposure 1 Working Level Month WLM is the exposure which a worker receives during 1 month (170 h) at 1 WL. During one year at 1 WL a worker receives 12 WLM. During one year at 1 WL a member of the public receives an exposure of 50 WLM. One working year has 2000 h, one year for a member of the public has 8760 h. The annual exposure in a home with 180 Bq m -3 1 WLM. (F = 0.4, 8760 h/year) With 7000 h/year one needs 230 Bq m -3 in a home for 1 WLM. What do we know about the risk? Miners General public (Rn in homes) 3

4 Mortality due to lung cancer in German uranium miners (Wismut Cohort), WLM = 0.19 (95% CI: 0.16; 0.22). A categorical excess relative risk (ERR) model for lung cancers and radon exposure with no age and time effect modifiers. The exposure category ERR fit parameters are shown as crosses in the graph with 2 SD and the central estimate (solid line) and 95% CI (dashed lines) from the model for the cohort risk (with internal comparison groups). Walsh et al. (2010) Radiation Res. 173(1) WLM for Lung cancer (miners) WLM = 0.19 Wismut (95% CI: 0.16; 0.22). Linear model without effect modification (except for Wismut) WLM = 0.19 corresponds to a risk of WLM -1 ERR 100 WLM = 0,59 (95% CI: 0,35; 1,0) UNCEAR (2006) Vol. II, Annex E (modified) Walsh et al. (2010) Radiation Research 173(1)

5 Recommended reading: UNSCEAR on attributability and uncertainties Annex A. Attributing health effects to ionizing radiation exposure and inferring risks Annex B. Uncertainties in risk estimates for radiationinduced cancer Modifying factors for the ERR/WLM in the case of lung cancer Time after exposure with increasing time after exposure the ERR/WLM decreases. Attained age, age at exposure with increasing age the ERR/WLM decreases. Rate of exposure Inverse dose rate effect in the case of high cumulative exposures Lubin 1994; NRC 1999; Vacquier et al. 2009; Howe et al. 2006; Tomasek et al. 2008; Walsh et al. 2010; Lane et al See e.g. Walsh et al., RPD (2014) 1 7 5

6 ERR/100 WLM for specific cancers in the Wismut Cohort of miners, Kreuzer et al. (2008, 2009); Walsh et al. (2010) Lung cancer mortality in German uranium miners (Wismut Cohort), WLM = 0.19 (95% CI: 0.16; 0.22). 200 Bq m WLM over a lifetime How large is the risk due to Radon in homes? Walsh et al. (2010) Radiation Res. 173(1)

7 Results of pooled studies: Lung cancer risk as a consequence of chronic exposure to average Radon concentrations in homes Study Europe (Darby et al. 2005) cases, controls North America (Krewski et al. 2005) cases, controls China (Lubin et al. 2005) cases, controls ERR/100 Bq m -3 95% CI 0,08 0,03 0,16 0,11 0,00 0,28 0,13 0,01-0,36 Relative lung cancer risk due to Radon exposure Relative risk Relative risks from: Indoor studies (case-control) Miner studies (cohorts) Ecological study by Cohen (1995) Log-linear fit to indoor data und 95% CI. Relative risk = 1 Radon concentration in Bq m -3 UNCEAR (2006) Vol. II, Annex E Lubin & Boyce (1997) J Natl Cancer Inst 89(1):

8 RR/100 Bq m -3 = 1,08 95% CI: 1,03 1,16 categories <25, 25 49, 50 99, , , and 800 Bq/m 3 Lung cancer and Radon in homes in Europe Relative risk of lung cancer according to the time weighted average observed residential radon concentration after stratification by study, age, sex, region of residence, and smoking habits. The relative risks and 95% confidence intervals are shown as estimated by the linear relationship RR = X (solid line), with 95% confidence limits (dashed lines). The relative risk is equal to 1 at 0 Bq/m 3. Darby et al. (2006) Scand J Work Environ Health 32, Suppl 1; 1-84 Lung cancer and Radon in homes in Europe Darby et al. (2006) Scand J Work Environ Health 32, Suppl 1;

9 Lung cancer and Radon in homes in North America. A combined analysis of 7 casecontrol-studies OR/100 Bq m -3 = 1,11 (95% CI 1,00 1,28) OR/100 Bq m -3 = 1,21 (95% CI 1,03 1,36) ORs and 95% CIs for categories of mean radon concentration within the 5- to 30-year exposure time window from the fitted model for the linear excess OR (solid line) and its 95% CIs (dotted lines). a. All data (n = cases, controls) and b. restricted data, limited to subjects residing in 1 or 2 residences during the 5- to 30-year exposure time window and at least 20 years coverage with -track monitors (n = cases, controls). Krewski et al. (2005) Epidemiology 16(2) OR/100 Bq m -3 = 1,33 (95% CI 1,01 1,36) Lung cancer and Radon in homes in China OR/100 Bq m -3 = 1,32 (95% CI 1,07 1,91) Odds ratios (OR) of lung cancer for categories of radon concentration for the Shenyang and Gansu case-control data, and ORs and the fitted linear odds ratio model (solid line) and 95% confidence limits (dashed lines) for the pooled data. Results are shown a. for all subjects b. for subjects with complete coverage of the 5 30 year exposure time window and resident in 1 home. Each OR is plotted at its categoryspecific mean concentration. Lubin et al. (2004) Int. J. Cancer 109,

10 Influence of the uncertainties of the exposure estimates in homes M. Kreuzer (2014) Correction for uncertainties of the exposure estimates in Darby et al. (2006) before and after RR/100 Bq m -3 = 1,08 95% CI: 1,03 1,16 RR/100 Bq m -3 = 1,16 95% CI: 1,03 1,31 Darby et al. (2006) Scand J Work Environ Health 32, Suppl 1; Fearn, Hill, Darby (2008) Statist. Med. 27:

11 Lung cancer and Radon in homes in Europe (upper panels: before and lower panels: after correction for the uncertainties of the exposure estimates) Darby et al. (2006) Scand J Work Environ Health 32, Suppl 1; 1-84 Cumulative frequencies of outdoors Radon concentrations in Germany (settlement areas, ) Cumulative frequency in % Rn-222 concentration in Bq m

12 Radon in homes in Western Germany Wicke & Schmier (1985) FS T Radon in Bq/m 3 Assuming a risk of lung cancer of about 16 % per 100 Bq/m 3 Rn-222, one obtains a cumulative absolute risk up to an age of 75 years to die from lung cancer: Radon in Bq m cigarette smokers 10,1 % 11,6 % 16,0 % 21,6 % life-long non-smokers 0,41 % 0,47 % 0,67 % 0,93 % S. Darby et al., BMJ, doi: /bmj Published

13 ICRP Publication ICRP Statement on Radon 2009 Conclusions of ICRP Statement on Radon (2009): The ICRP proposed a nominal risk coefficient of WLM -1 = (Bq h m -3 ) -1 to replace the ICRP 65 (1993) value of WLM -1 The upper value of reference level for homes was lowered from 600 Bq m -3 to 300 Bq m -3 and 1000 Bq m -3 was specified as an entry point for applying occupational protection requirements. The Statement on Radon recommended the use of the value of WLM -1 = (Bq h m -3 ) -1 for radiation protection purposes. But said intention that ICRP would in future publish dose coefficients for Rn isotopes calculated by biokinetic and dosimetric models. 13

14 Quantification of Radon exposure: Derivation of the effective dose per WLM Epidemiological approach risk per WLM risk per Sv = Sv per WLM Dosimetric approach Calculation of the effective dose by means of models Epidemiological approach - old ICRP 65 (1993) convention of dose conversion Compare the risk of lung cancer in miners 2,83 x 10-4 per WLM with the total detriment (cancer & hereditary effects according to ICRP 60 (1991)): adults 5,6 x 10-2 per Sv 5 msv per WLM total 7,3 x 10-2 per Sv 4 msv per WLM 14

15 Epidemiological approach old risk 1 per WLM risk 2 per Sv 2, per WLM = = 5 msv per WLM 3 5, per Sv all ages 1 ICRP 65 (1993) convention of dose conversion 2 Compare the risk of lung cancer in miners with the total detriment (cancer & hereditary effects acc. to ICRP 60 (1991). 3 adults 4 msv per WLM Detriments acc. to ICRP 60/103 in 10 2 pro Sv ICRP 60 (1991) cancer hereditary total lung total effects adults 0,6 4,8 0,8 5,6 total 0,8 6,0 1,3 7,3 ICRP 103 (2007) adults 1,2 4,1 0,1 4,2 total 0,9 5,5 0,2 5,7 15

16 Epidemiological approach revised With a risk coefficient for lung cancer of per WLM detriment (ICRP 103) adults Sv msv WLM -1 total Sv -1 9 msv WLM -1 old ICRP 65 values: adults 5 msv WLM -1 total 4 msv WLM -1 Epidemiological approach revised risk 1 per WLM risk 2 per Sv per WLM = 9 msv per WLM 5, per Sv all ages 3 1 ICRP 115 (2009) 2 Compare the risk of lung cancer in miners with the total detriment (cancer & hereditary effects according to ICRP 103 (2007). 3 adults 12 msv per WLM 16

17 Epidemiological approach revised risk 1 / (Bq h m -3 ) /(Bq h m -3 ) = 14 nsv /(Bq h m -3 ) risk 2 / Sv 5, / Sv all ages 3 1 ICRP 115 (2009) 2 Compare the risk of lung cancer in miners with the total detriment (cancer & hereditary effects according to ICRP 103 (2007). 3 adults 19 nsv /(Bq h m -3 ) Dosimetric approach for inhaled 222 Rn + progeny Rn-222 concentration potential alpha-energy concentration relative size distribution equilibrium factor unattached fraction aerosol fraction biokinetic and dosimetric Models radiation-weighting factors, w R = 20 tissue-weighting factors, w T = 0.12 intake by inhalation mean absorbed dose, D T,R to lung tissues, Gy equivalent dose, H T, to lungs, Sv effective dose, E ICRP 66 (1994) 17

18 Human Respiratory Tract Model: ICRP 66 (1994) Extrathoracal air passages ET 1 ET 2 Bronchial regions BB Bronchiolar regions Alveolar-interstitial regions bb Al Factors influencing the dosimetric calculations Aerosol characteristics unattached fraction (1-f P ) size distribution (AMAD) equilibrium factor (F) rate of inhalation absorption of Rn progeny systemic biokinetic 18

19 ICRP dose coefficients: dosimetric approach preliminary values equi- unatt- effective librium ached dose in msv factor fraction, % per WLM homes work places mines For comparison, the revised epidemiological approach according to ICRP 115 (2009) with a risk of lung cancer: per WLM yields adults detriment Sv msv WLM -1 total detriment Sv -1 9 msv WLM -1 Harrison, IRPA (2014) 19

20 Reference values for Radon exposure WHO (2009) National reference level 100 Bq m -3 (maximal 300 Bq m -3 ) ICRP (2009) homes 300 Bq m -3 Work places 1000 Bq m -3 Directive 2013/59/EURATOM dated Reference value 300 Bq m Bq m -3 supposedly corresponds in the future to an effective dose of 20 msv per year. I did not find a rationale for the reference values! 20

21 I just found this! Stiftung Warentest. Fünf Tote jeden Tag. (Five deaths every day) Test, August 2011: This would be the right map! Average Radon concentration in homes in Bq/m 3 Percentage of collective Radon exposure of the general public in administrative districts in Germany (population mean Rn concentration). S. Menzler, A. Schaffrath-Rosario, H.E. Wichmann, L. Kreienbrock: Abschätzung des attributablen Lungenkrebsrisikos in Deutschland durch Radon in Wohnungen. Ecomed-Verlag Landsberg,

22 Some statistics 1 population Germany ,18E+07 2 mortality rate Germany per year 3 cancer deaths Germany per year 4 lung cancer deaths Germany per year 5 lung cancer deaths due to Radon in Germany? per year relative cancer mortality risk 2010 (3/2) 0,254 relative lung cancer mortality risk 2010 (4/2) 0,050 relative Rn lung cancer mortality risk (5/2) 0,011 absolute mortality risk 2010 (2/1) 0,0105 per year absolute cancer mortality risk 2010 (3/1) 0,0027 per year absolute lung cancer mortality risk 2010 (4/1) 0,00053 per year absolute Rn lung cancer mortality risk (5/1) 3E-5 per year ,5 0,2 0,1 Total death probability in % per year Annual death risk (extremes) for 18 countries which are considered safe. ICRP 60 0,05 0,02 0,01 absolute mean Radon lung cancer mortality risk , ,003 Age in years 22

23 Rate per Spontaneous incidence of cancer age specific mortality of white US citizens (without melanomas) 1 BEIR (1980) 0, Age at risk Absolute risk to die from lung cancer up to an age of 70 years for: Radon, smoking and lung cancer Life-long nonsmokers Smokers (15 24 cigarettes per day up to an age of 30 years) Smokers (15 24 cigarettes per day up to an age of 50 years) Smokers (15 24 cigarettes per day up to an age of 75 years) Translated from: Brüske-Hohlfeld, Kreienbock, Wichmann, mensch+umwelt spezial 18. Ausgabe 2006, 37 23

24 Number of deaths due to lung cancer per year in Germany which are calculated to be avoidable by limiting the Radon exposure Limit in number of avoidable deaths (outdoors air) hypothetical victims We have a problem of invisible deaths! Translated from Brüske-Hohlfeld, Kreienbock, Wichmann, mensch+umwelt spezial 18. Ausgabe 2006, 37 Lung cancer deaths avoidable by limiting the Radon concentrations in homes in Germany Avoidable lung cancer deaths 9 Bq/m 3 Mission impossible! Radon maximum value in Bq/m 3 Daten aus S. Menzler, A. Schaffrath-Rosario, H.E. Wichmann, L. Kreienbrock: Abschätzung des attributablen Lungenkrebsrisikos in Deutschland durch Radon in Wohnungen. Ecomed-Verlag Landsberg,

25 Lung cancer deaths avoidable by limiting the Radon concentrations in homes in Germany Daten aus S. Menzler, A. Schaffrath-Rosario, H.E. Wichmann, L. Kreienbrock: Abschätzung des attributablen Lungenkrebsrisikos in Deutschland durch Radon in Wohnungen. Ecomed-Verlag Landsberg, 2006 Summary We have good epidemiological data for lung cancer and Radon exposure in homes and in mines. Model uncertainties represent a major problem for the miner studies. The ICRP Statement on Radon of 2009 appears premature given the results of the Wismut Cohort. Studies of Radon in homes and miner studies yield coarsely consistent results. However, the miner data are not significantly raised in the concentration range relevant for most homes. The pooled studies on Radon in homes yield significantly enhanced risks with risk coefficients of 8 16 % per 100 Bq/m 3 Rn-222. The lung cancer risk due to Radon can be managed by limiting Radon concentrations in Bq m -3. No dose coefficients are needed for the limitation. But, no real rationale exists for setting the limits. The ICRP (2009) has adopted a new risk coefficient of per WLM which would approximately double the dose coefficient in the epidemiological approach. The ICRP intends to publish new dose coefficients for inhalation & ingestion of Radon and Rn progeny: for work places, mines and homes. The ICRP recommends an upper reference value of 300 Bq m -3 for private homes 20 msv effective dose per year (new epidemiological approach). Collective dose and attributability considerations make the limitation approach questionable. 25

26 Open questions: A question for society: How do we handle risks? A question for radiation protection: How do we set the limits? A question for politics: What do we get for protection against Radon? A question for normal people: Is it safe to live in my home? LNT EAR HRTM PAEC BB WLM PAR Rn ERR OR Rn FP Bq h m -3 F ET 1 msv EEC 95% CI AL AMAD f P PAC RR ET 2 WL detriment pci L -1 Bq m -3 bb msv/(bq m -3 ) The End 26