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Indoor Radon Risk What do we know and how do we know it? HPS Annual Meeting July 14, 2009 Jan Johnson, PhD, CHP Tetra Tech.

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Presentation on theme: "Indoor Radon Risk What do we know and how do we know it? HPS Annual Meeting July 14, 2009 Jan Johnson, PhD, CHP Tetra Tech."— Presentation transcript:

1 Indoor Radon Risk What do we know and how do we know it? HPS Annual Meeting July 14, 2009 Jan Johnson, PhD, CHP Tetra Tech

2 Public - Mixed Messages

3 What do we know: Real problem or unnecessary concern? Underground miner studies Underground miner studies Indoor radon epidemiological studies (1972 – present) Indoor radon epidemiological studies (1972 – present) –Europe –US and Canada 1984: Watras House – Public Awareness – EPA Action 1984: Watras House – Public Awareness – EPA Action National Academy of Sciences/National Research Council Reports (BEIR IV and BEIR VI) National Academy of Sciences/National Research Council Reports (BEIR IV and BEIR VI) Recent results of pooled epidemiologic studies Recent results of pooled epidemiologic studies Dosimetry Dosimetry

4 BEIR VI Reprise - 1999 What did BEIR VI tell us? What did BEIR VI tell us? How does that relate to information available since BEIR VI was written? How does that relate to information available since BEIR VI was written? Does new information support or contradict BEIR VI? Does new information support or contradict BEIR VI?

5 Lifetime Relative Risk Model ERR = β(ω 5-14 +θ 15-24 ω 15-24 +θ 25+ ω 25+ )Φ age γ z where: ω = exposure during given time period θ = weighting factor (time since exposure) θ = weighting factor (time since exposure) β = slope of the exposure-risk relationship β = slope of the exposure-risk relationship Φ = age effect (ERR declines with Φ = age effect (ERR declines with increasing age) γ = exposure rate adjustment factor γ = exposure rate adjustment factor (duration or concentration)

6 Elements of the BEIR VI Risk Model (Based primarily on miner data) Excess relative risk declines with age Excess relative risk declines with age –Relative risk is the risk of the disease with the exposure divided by risk of the disease without exposure Risk declines with time since exposure Risk declines with time since exposure –Total effective exposure = ω 5-14 +θ 15-24 ω 15-24 +θ 25+ ω 25+ Exposures in the last 5 years do not contribute to the risk Exposures in the last 5 years do not contribute to the risk Risk is dependent on dose rate – inverse dose rate effect Risk is dependent on dose rate – inverse dose rate effect –Expressed as a factor of duration of exposure or concentration

7 Estimated Relative Lifetime Risk Exposure Age Concentration Model WL M/y pCi/L Male smoker Male non sm Female smoker Female non sm 0.191.41.161.391.181.41 0.392.71.321.781.351.82 0.785.41.622.541.692.64 1.5610.82.174.062.354.26 3.1221.63.127.013.557.44

8 Estimated Relative Lifetime Risk Exposure Age Duration Model WLM per yr pCi/L Male smoker Male non s Female smoker Female non s 0.191.41.111.261.121.27 0.392.71.211.521.241.55 0.785.41.422.031.472.09 1.5610.81.813.051.923.17 3.1221.62.515.062.765.32

9 Estimated Attributable Risk (Risk of LC death due to radon/total risk of LC death) ModelPopulationSmokers Non- smokers Males E-A-Conc.0.1410.1250.258 E-A-Dur.0.0990.0870.189 Females E-A-Conc.0.1530.1370.269 E-A-Dur.0.1080.0960.197

10 Estimated Number of Lung Cancer Deaths in the US Attributable to Radon (1995) Total No. of U.S. LC Deaths Est. Radon LC Deaths E-A-C Model Est. Radon LC Deaths E-A-D Model Total population 157,40021,80015,400 Smokers146,40018,90013,300 Non- smokers 11,0002,9002,100

11 BEIR VI Conclusions Radon in homes is expected to be a cause of lung cancer in the general public. Radon in homes is expected to be a cause of lung cancer in the general public. Adjustment factor for risk per WLM in mines to risk in homes (k) = 1 Adjustment factor for risk per WLM in mines to risk in homes (k) = 1 Number of lung cancer cases due to residential radon exposure in the US projected to be 15,400 to 21,800. Number of lung cancer cases due to residential radon exposure in the US projected to be 15,400 to 21,800. Uncertainty analyses suggest that the number of radon-related cases could range from 3,000 to 33,000. Uncertainty analyses suggest that the number of radon-related cases could range from 3,000 to 33,000. Indoor radon is the second leading cause of lung cancer after cigarette smoking. Indoor radon is the second leading cause of lung cancer after cigarette smoking. Approximately 1/3 of radon-related lung cancer cases could be avoided if all homes had concentrations below 4 pCi/L. Approximately 1/3 of radon-related lung cancer cases could be avoided if all homes had concentrations below 4 pCi/L.

12 Lifetime Risk of Lung Cancer From Radon Decay Products 70% indoor occupancy; 70 years of exposure (2003 EPA estimates based on BEIR VI) Average Rn Conc. (pCi/L) Never Smokers Current Smokers 8 14 in 1,000 12 in 100 4 7 in 1,000 6 in 100 2 3.5 in 1,000 3 in 100

13 Recent Epidemiologic Analyses Low Exposure Miner Data (1997) Low Exposure Miner Data (1997) Pooled Indoor Radon Studies Pooled Indoor Radon Studies –North-American Pooled Study (2005-06) –European Pooled Study (2005-06) –Chinese Pooled Study (2004)

14 Cum. Exp. (WLM) No. of Cases Mean(WLM) Relative Risk 95% CI 011501.00na 0.1 – 3.5562.41.371.0 – 2.0 3.6 – 6.9565.31.140.8 – 1.7 7.0 – 15.15612.41.160.8 – 1.7 Pooled Low Exposure Miner Studies Occupational Exposure 0 – 15 WLM

15 Cum. Exp. (WLM) No. of Cases Mean (WLM) Relative risk 95% CI 15.2 – 21.2 5717.31.45 1.0 – 2.2 21.3 – 35.4 5633.11.50 1.0 – 2.2 35.5 – 43.5 5738.61.53 1.0 – 2.2 43.6 – 59.4 5653.21.69 1.1 – 2.5 59.5 – 70.3 5663.31.78 1.2 – 2.6 70.4 – 86.5 5681.11.68 1.1 – 2.5 86.6 – 99.9 5691.41.86 1.2 – 2.8 Pooled Low Exposure Miner Studies Occupational Exposure 15 - 100 WLM

16 Study No. of studies pooled Cases Controls Increased risk at 100 Bq m -3 (95% CI) Inc. Risk at 100 Bq m -3 (improved Rn Conc.) (95% CI) North American 7 3,662 4,966 11% (0% - 28%) 18% (2%-43%) European 13 7,148 14,208 8% (3% - 16%) 16% (5%-31%) Chinese 2 1,050 1,995 13% (1% - 36%) Results of Pooled Residential Studies

17 Excess Relative Risks at Lifetime Exposure at 100 Bq m -3 (~30 WLM) Source Estimated Excess Relative Risk (95% CI) Low Exposure Miner Data 0.50 (0.0 – 1.2) NA Pooled Study 0.18 (0.02 – 0.43) European Pooled Study 0.16 (0.05 – 0.31) Chinese Pooled Study 0.13 (0.01 – 0.36) BEIR VI (duration model) 0.22 smkr – 0.53 nsmkr BEIR VI (conc. model) 0.33 smkr – 0.80 nsmkr

18 Estimated Dose Coefficients Reference Dose Coeff. mSv/WLMBasis ICRP 65 (93) ICRP 103 (07) 4 – 5 Epidemiology/ Observed Risk UNSCEAR (2000) 6 (wide range of estimates) Lung dosimetry James (2004) 15.5 – 21.4 Lung dosimetry NCRP 160 (2009) 10 Lung dosimetry average value

19 Estimated Lifetime Risk Based on Dose Coefficients at 100 Bq m -3 Assumptions Assumptions –70 years of exposure, 7000 hours per year, equilibrium factor = 0.4 –100 Bq m -3 = 31 WLM –Dose coefficient = 10 mSv WLM -1 –Risk coefficient = 0.05 Sv -1 Estimated lifetime risk from RnD = 0.02 Estimated lifetime risk from RnD = 0.02 EPA estimated lifetime risk at 100 Bq m -3 EPA estimated lifetime risk at 100 Bq m -3 –Smoker – 0.04 –Non-smoker – 0.005

20 SMOKING The Elephant in the Room Pooled indoor radon studies – Overall lung cancer risk for smokers is about 25 times the lung cancer risk for non-smokers Pooled indoor radon studies – Overall lung cancer risk for smokers is about 25 times the lung cancer risk for non-smokers Contrary to previous opinions, radon-related lung cancer can occur in non-smokers as well as smokers Contrary to previous opinions, radon-related lung cancer can occur in non-smokers as well as smokers –BEIR VI Excess Relative Risk for non-smokers greater than 2 x the Excess Relative Risk for smokers. –Pooled indoor radon epidemiological studies showed no difference between the relative risk for smokers and non-smokers Uncertainty in smoking data, other exposures Uncertainty in smoking data, other exposures

21 What does it all mean for public policy?

22 HPS Revised Position Paper In 2007 Health Physics Society Board appointed an Ad Hoc Committee to update the 1990 Indoor Radon Position Statement In 2007 Health Physics Society Board appointed an Ad Hoc Committee to update the 1990 Indoor Radon Position Statement –Committee composed of health physicists, epidemiologists, EPA representatives, American Lung Association, State Health Department –Draft Position Statement approved with minor editorial changes by the Scientific and Public Issues Committee in February 2009 –Draft background document completed in May 2009 –Position Statement to be presented to the Board in July?


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