Indoor Radon RiskIndoor Radon RiskWhat do we know and how What do we know and how

do we know it?do we know it?

HPS Annual MeetingHPS Annual MeetingJuly 14, 2009July 14, 2009

Jan Johnson, PhD, CHPJan Johnson, PhD, CHPTetra TechTetra Tech

Public - Mixed Public - Mixed MessagesMessages

What do we know: Real What do we know: Real problem or unnecessary problem or unnecessary

concern?concern? Underground miner studiesUnderground miner studies Indoor radon epidemiological studies (1972 – Indoor radon epidemiological studies (1972 –

present)present)– EuropeEurope– US and CanadaUS and Canada

1984: Watras House – Public Awareness – EPA 1984: Watras House – Public Awareness – EPA ActionAction

National Academy of Sciences/National National Academy of Sciences/National Research Council Reports (BEIR IV and BEIR VI)Research Council Reports (BEIR IV and BEIR VI)

Recent results of pooled epidemiologic studiesRecent results of pooled epidemiologic studies DosimetryDosimetry

BEIR VI Reprise - 1999BEIR VI Reprise - 1999

What did BEIR VI tell us?What did BEIR VI tell us? How does that relate to information How does that relate to information

available since BEIR VI was written?available since BEIR VI was written? Does new information support or Does new information support or

contradict BEIR VI?contradict BEIR VI?

Lifetime Relative Risk ModelLifetime Relative Risk Model

ERR = ERR = ββ((ωω5-145-14++θθ15-2415-24ωω15-2415-24++θθ25+25+ωω25+25+))ΦΦageageγγzz

where: where: ω ω = exposure during given time period= exposure during given time period θ θ = weighting factor (time since = weighting factor (time since

exposure)exposure) β β = slope of the exposure-risk = slope of the exposure-risk

relationshiprelationship ΦΦ = age effect (ERR declines with = age effect (ERR declines with

increasing age)increasing age) γγ = exposure rate adjustment factor = exposure rate adjustment factor

(duration or concentration)(duration or concentration)

Elements of the BEIR VI Risk Elements of the BEIR VI Risk Model (Based primarily on Model (Based primarily on

miner data)miner data) Excess relative risk declines with ageExcess relative risk declines with age

– Relative risk is the risk of the disease with Relative risk is the risk of the disease with the exposure divided by risk of the disease the exposure divided by risk of the disease without exposurewithout exposure

Risk declines with time since exposureRisk declines with time since exposure– Total “effective” exposure = Total “effective” exposure =

ωω5-145-14++θθ15-2415-24ωω15-2415-24++θθ25+25+ωω25+25+

Exposures in the last 5 years do not Exposures in the last 5 years do not contribute to the riskcontribute to the risk

Risk is dependent on dose rate – inverse Risk is dependent on dose rate – inverse dose rate effectdose rate effect– Expressed as a factor of duration of exposure Expressed as a factor of duration of exposure

or concentrationor concentration

Estimated Relative Lifetime Estimated Relative Lifetime RiskRisk

Exposure Age Concentration Exposure Age Concentration ModelModel

WLWLM/yM/y

pCi/LpCi/L Male Male smokersmoker

Male Male non smnon sm

Female Female smokersmoker

Female Female non smnon sm

0.10.199

1.41.4 1.161.16 1.391.39 1.181.18 1.411.41

0.30.399

2.72.7 1.321.32 1.781.78 1.351.35 1.821.82

0.70.788

5.45.4 1.621.62 2.542.54 1.691.69 2.642.64

1.51.566

10.810.8 2.172.17 4.064.06 2.352.35 4.264.26

3.13.122

21.621.6 3.123.12 7.017.01 3.553.55 7.447.44

Estimated Relative Lifetime Estimated Relative Lifetime RiskRisk

Exposure Age Duration ModelExposure Age Duration ModelWLM WLM per yrper yr

pCi/LpCi/L Male Male smokersmoker

Male Male non snon s

Female Female smokesmokerr

Female Female non snon s

0.190.19 1.41.4 1.111.11 1.261.26 1.121.12 1.271.27

0.390.39 2.72.7 1.211.21 1.521.52 1.241.24 1.551.55

0.780.78 5.45.4 1.421.42 2.032.03 1.471.47 2.092.09

1.561.56 10.810.8 1.811.81 3.053.05 1.921.92 3.173.17

3.123.12 21.621.6 2.512.51 5.065.06 2.762.76 5.325.32

Estimated Attributable RiskEstimated Attributable Risk((Risk of LC death due to radon/total risk Risk of LC death due to radon/total risk

of LC death)of LC death)

ModelModel PopulationPopulation SmokersSmokers Non-Non-smokerssmokers

MalesMales

E-A-Conc.E-A-Conc. 0.1410.141 0.1250.125 0.2580.258

E-A-Dur.E-A-Dur. 0.0990.099 0.0870.087 0.1890.189

FemalesFemales

E-A-Conc.E-A-Conc. 0.1530.153 0.1370.137 0.2690.269

E-A-Dur.E-A-Dur. 0.1080.108 0.0960.096 0.1970.197

Estimated Number of Lung Cancer Estimated Number of Lung Cancer Deaths in the US Attributable to Radon Deaths in the US Attributable to Radon

(1995)(1995)

Total No. Total No. of U.S. LC of U.S. LC DeathsDeaths

Est. Est. Radon LC Radon LC DeathsDeathsE-A-C ModelE-A-C Model

Est. Est. Radon LC Radon LC DeathsDeathsE-A-D ModelE-A-D Model

Total Total populatiopopulationn

157,400157,400 21,80021,800 15,40015,400

SmokersSmokers 146,400146,400 18,90018,900 13,30013,300

Non-Non-smokerssmokers

11,00011,000 2,9002,900 2,1002,100

BEIR VI ConclusionsBEIR VI Conclusions Radon in homes is expected to be a cause of Radon in homes is expected to be a cause of

lung cancer in the general public.lung cancer in the general public. Adjustment factor for risk per WLM in mines Adjustment factor for risk per WLM in mines

to risk in homes (k) = 1to risk in homes (k) = 1 Number of lung cancer cases due to Number of lung cancer cases due to

residential radon exposure in the US residential radon exposure in the US projected to be 15,400 to 21,800.projected to be 15,400 to 21,800.

Uncertainty analyses suggest that the number Uncertainty analyses suggest that the number of radon-related cases could range from 3,000 of radon-related cases could range from 3,000 to 33,000.to 33,000.

Indoor radon is the second leading cause of Indoor radon is the second leading cause of lung cancer after cigarette smoking.lung cancer after cigarette smoking.

Approximately 1/3 of radon-related lung Approximately 1/3 of radon-related lung cancer cases could be avoided if all homes cancer cases could be avoided if all homes had concentrations below 4 pCi/L.had concentrations below 4 pCi/L.

Lifetime Risk of Lung Cancer Lifetime Risk of Lung Cancer From Radon Decay ProductsFrom Radon Decay Products70% indoor occupancy; 70 years of exposure70% indoor occupancy; 70 years of exposure

(2003 EPA estimates based on BEIR VI)(2003 EPA estimates based on BEIR VI)

Average Rn Average Rn Conc. (pCi/L)Conc. (pCi/L)

Never Never SmokersSmokers

Current Current SmokersSmokers

88 14 in 1,00014 in 1,000 12 in 10012 in 100

44 7 in 1,0007 in 1,000 6 in 1006 in 100

22 3.5 in 1,0003.5 in 1,000 3 in 1003 in 100

Recent Epidemiologic Recent Epidemiologic AnalysesAnalyses

Low Exposure Miner Data (1997)Low Exposure Miner Data (1997) Pooled Indoor Radon StudiesPooled Indoor Radon Studies

– North-American Pooled Study (2005-06)North-American Pooled Study (2005-06)– European Pooled Study (2005-06)European Pooled Study (2005-06)– Chinese Pooled Study (2004)Chinese Pooled Study (2004)

Cum. Exp. Cum. Exp. (WLM)(WLM)

No. of No. of CasesCases

MeanMean(WLM)(WLM)

Relative Relative RiskRisk

95% CI95% CI

0 115 0 1.00 na

0.1 – 3.5 56 2.4 1.37 1.0 – 2.0

3.6 – 6.9 56 5.3 1.14 0.8 – 1.7

7.0 – 15.1 56 12.4 1.16 0.8 – 1.7

Pooled Low Exposure Miner Pooled Low Exposure Miner StudiesStudies

Occupational Exposure 0 – 15 WLMOccupational Exposure 0 – 15 WLM

Cum. Exp. Cum. Exp. (WLM)(WLM)

No. of No. of CasesCases

Mean Mean (WLM)(WLM)

Relative Relative riskrisk

95% CI95% CI

15.2 – 21.215.2 – 21.2 5757 17.317.3 1.451.45 1.0 – 2.21.0 – 2.2

21.3 – 35.421.3 – 35.4 5656 33.133.1 1.501.50 1.0 – 2.21.0 – 2.2

35.5 – 43.535.5 – 43.5 5757 38.638.6 1.531.53 1.0 – 2.21.0 – 2.2

43.6 – 59.443.6 – 59.4 5656 53.253.2 1.691.69 1.1 – 2.51.1 – 2.5

59.5 – 70.359.5 – 70.3 5656 63.363.3 1.781.78 1.2 – 2.61.2 – 2.6

70.4 – 86.570.4 – 86.5 5656 81.181.1 1.681.68 1.1 – 2.51.1 – 2.5

86.6 – 99.986.6 – 99.9 5656 91.491.4 1.861.86 1.2 – 2.81.2 – 2.8

Pooled Low Exposure Miner Pooled Low Exposure Miner StudiesStudies

Occupational Exposure 15 - 100 WLMOccupational Exposure 15 - 100 WLM

StudyNo. 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

3,6624,966

11%(0% - 28%)

18%(2%-43%)

European 137,148

14,2088%

(3% - 16%)16%

(5%-31%)

Chinese 21,0501,995

13%(1% - 36%)

Results of Pooled Residential StudiesResults of Pooled Residential Studies

Excess Relative Risks at Excess Relative Risks at Lifetime Exposure at 100 Bq mLifetime Exposure at 100 Bq m--

33 (~30 WLM) (~30 WLM)SourceSource Estimated ExcessEstimated Excess

Relative Risk Relative Risk (95% (95% CI)CI)

Low Exposure Miner Low Exposure Miner DataData

0.50 0.50 (0.0 – 1.2)(0.0 – 1.2)

NA Pooled StudyNA Pooled Study 0.18 0.18 (0.02 – 0.43)(0.02 – 0.43)

European Pooled European Pooled StudyStudy

0.16 0.16 (0.05 – 0.31)(0.05 – 0.31)

Chinese Pooled StudyChinese Pooled Study 0.13 0.13 (0.01 – 0.36)(0.01 – 0.36)

BEIR VI (duration BEIR VI (duration model)model)

0.22 smkr – 0.53 0.22 smkr – 0.53 nsmkrnsmkr

BEIR VI (conc. model)BEIR VI (conc. model) 0.33 smkr – 0.80 0.33 smkr – 0.80 nsmkrnsmkr

Estimated Dose CoefficientsEstimated Dose Coefficients

ReferenceReference Dose Coeff.Dose Coeff.

mSv/WLMmSv/WLMBasisBasis

ICRP 65 (93)ICRP 65 (93)

ICRP 103 (07)ICRP 103 (07)4 – 54 – 5 Epidemiology/Epidemiology/

Observed Risk Observed Risk

UNSCEAR UNSCEAR (2000)(2000)

6 (wide range 6 (wide range of estimates)of estimates)

Lung Lung dosimetrydosimetry

James (2004)James (2004) 15.5 – 21.415.5 – 21.4 Lung Lung dosimetrydosimetry

NCRP 160 NCRP 160 (2009)(2009)

1010 Lung Lung dosimetry dosimetry average valueaverage value

Estimated Lifetime Risk Based Estimated Lifetime Risk Based on Dose Coefficients at 100 Bq on Dose Coefficients at 100 Bq

mm-3-3 AssumptionsAssumptions

– 70 years of exposure, 7000 hours per year, 70 years of exposure, 7000 hours per year, equilibrium factor = 0.4equilibrium factor = 0.4

– 100 Bq m100 Bq m-3-3 = 31 WLM = 31 WLM– Dose coefficient = 10 mSv WLMDose coefficient = 10 mSv WLM-1-1

– Risk coefficient = 0.05 SvRisk coefficient = 0.05 Sv-1-1

Estimated lifetime risk from RnD = 0.02Estimated lifetime risk from RnD = 0.02 EPA estimated lifetime risk at 100 Bq mEPA estimated lifetime risk at 100 Bq m-3-3

– Smoker – 0.04Smoker – 0.04– Non-smoker – 0.005Non-smoker – 0.005

SMOKINGSMOKING The Elephant in the RoomThe Elephant in the Room

Pooled indoor radon studies – Overall lung Pooled indoor radon studies – Overall lung cancer risk for smokers is about 25 times the cancer risk for smokers is about 25 times the lung cancer risk for non-smokerslung cancer risk for non-smokers

Contrary to previous opinions, radon-related Contrary to previous opinions, radon-related lung cancer can occur in non-smokers as well lung cancer can occur in non-smokers as well as smokersas smokers– BEIR VI Excess Relative Risk for non-smokers BEIR VI Excess Relative Risk for non-smokers

greater than 2 x the Excess Relative Risk for greater than 2 x the Excess Relative Risk for smokers.smokers.

– Pooled indoor radon epidemiological studies Pooled indoor radon epidemiological studies showed no difference between the relative risk for showed no difference between the relative risk for smokers and non-smokerssmokers and non-smokers

Uncertainty in smoking data, other exposures Uncertainty in smoking data, other exposures

What does it all mean for public What does it all mean for public policy?policy?

HPS Revised Position PaperHPS Revised Position Paper

In 2007 Health Physics Society Board In 2007 Health Physics Society Board appointed an Ad Hoc Committee to appointed an Ad Hoc Committee to update the 1990 Indoor Radon Position update the 1990 Indoor Radon Position StatementStatement– Committee composed of health physicists, Committee composed of health physicists,

epidemiologists, EPA representatives, American Lung epidemiologists, EPA representatives, American Lung Association, State Health DepartmentAssociation, State Health Department

– Draft Position Statement approved with minor Draft Position Statement approved with minor editorial changes by the Scientific and Public Issues editorial changes by the Scientific and Public Issues Committee in February 2009Committee in February 2009

– Draft background document completed in May 2009Draft background document completed in May 2009– Position Statement to be presented to the Board in Position Statement to be presented to the Board in

July?July?