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Indoor Radon Risk What do we know and how do we know it?

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. Public - Mixed Messages. What do we know: Real problem or unnecessary concern?. Underground miner studies Indoor radon epidemiological studies (1972 – present)

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Indoor Radon Risk What do we know and how do we know it?

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  1. Indoor Radon RiskWhat 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 • Indoor radon epidemiological studies (1972 – present) • Europe • US and Canada • 1984: Watras House – Public Awareness – EPA Action • National Academy of Sciences/National Research Council Reports (BEIR IV and BEIR VI) • Recent results of pooled epidemiologic studies • Dosimetry

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

  5. Lifetime Relative Risk Model ERR = β(ω5-14+θ15-24ω15-24+θ25+ω25+)Φageγz where: ω = exposure during given time period θ = weighting factor (time since exposure) β = slope of the exposure-risk relationship Φ = age effect (ERR declines with increasing age) 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 • 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 • Total “effective” exposure = ω5-14+θ15-24ω15-24+θ25+ω25+ • Exposures in the last 5 years do not contribute to the risk • Risk is dependent on dose rate – inverse dose rate effect • Expressed as a factor of duration of exposure or concentration

  7. Estimated Relative Lifetime RiskExposure Age Concentration Model

  8. Estimated Relative Lifetime RiskExposure Age Duration Model

  9. Estimated Attributable Risk(Risk of LC death due to radon/total risk of LC death)

  10. Estimated Number of Lung Cancer Deaths in the US Attributable to Radon (1995)

  11. BEIR VI Conclusions • 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 • 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. • 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.

  12. Lifetime Risk of Lung Cancer From Radon Decay Products70% indoor occupancy; 70 years of exposure(2003 EPA estimates based on BEIR VI)

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

  14. Pooled Low Exposure Miner StudiesOccupational Exposure 0 – 15 WLM

  15. Pooled Low Exposure Miner StudiesOccupational Exposure 15 - 100 WLM

  16. Results of Pooled Residential Studies

  17. Excess Relative Risks at Lifetime Exposure at 100 Bq m-3 (~30 WLM)

  18. Estimated Dose Coefficients

  19. Estimated Lifetime Risk Based on Dose Coefficients at 100 Bq m-3 • 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 • EPA estimated lifetime risk at 100 Bq m-3 • Smoker – 0.04 • Non-smoker – 0.005

  20. SMOKINGThe 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 • 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

  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 • 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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