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RSI Study: Assessment of Lung Cancer Risk Associated with Radon in Natural Gas
 

RSI Study: Assessment of Lung Cancer Risk Associated with Radon in Natural Gas

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Risk Sciences International issued this analysis (on July 4, 2012) of the potential for lung cancer in New York State as a result of Marcellus Shale natural gas being used. The report finds the risks ...

Risk Sciences International issued this analysis (on July 4, 2012) of the potential for lung cancer in New York State as a result of Marcellus Shale natural gas being used. The report finds the risks negligible.

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    RSI Study: Assessment of Lung Cancer Risk Associated with Radon in Natural Gas RSI Study: Assessment of Lung Cancer Risk Associated with Radon in Natural Gas Document Transcript

    • FINAL REPORT An Assessment of the Lung Cancer RiskAssociated with the Presence of Radon in NaturalGas Used for Cooking in Homes in New York State July 4, 2012 325 DALHOUSIE STREET, 10TH FLOOR | OTTAWA, ON K1N 7G2 | CANADA | TEL: 613.260.1424 | FAX: 613.260.1443
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas Contents1. BACKGROUND ............................................................................................................................................... 3 RADON AND LUNG CANCER ..............................................................................................................................................32. RISK ASSESSMENT – BASE CASE SCENARIO .................................................................................................... 7 CONCENTRATION OF RADON IN NATURAL GAS IN THE PIPELINE ...............................................................................................7 USE OF NATURAL GAS FOR COOKING .................................................................................................................................9 DILUTION AND VENTILATION ..........................................................................................................................................10 ADJUSTMENT FOR RESIDENTIAL OCCUPANCY .....................................................................................................................11 RISK COEFFICIENT .........................................................................................................................................................113. SENSITIVITY ANALYSIS ................................................................................................................................. 12 LEVEL OF RADON IN NATURAL GAS ..................................................................................................................................12 INTENSITY OF USE OF GAS STOVES AND USE OF NATURAL GAS WATER HEATERS ......................................................................12 SIZE OF RESIDENCE .......................................................................................................................................................12 EXTENT OF VENTILATION ...............................................................................................................................................13 OCCUPANCY FRACTION .................................................................................................................................................13 RISK COEFFICIENTS .......................................................................................................................................................13 COMBINED SENSITIVITY ANALYSES ...................................................................................................................................13 RESULTS OF SENSITIVITY ANALYSIS ...................................................................................................................................134. REFERENCES ................................................................................................................................................ 175. CONTRIBUTORS ........................................................................................................................................... 19July 4, 2012 Page ii
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas 1. BackgroundRadon is a well-established risk factor for human lung cancer. Because radon released from the earth’scrust can make its way into the home environment, the U.S. Environmental Protection Agency has set aguideline of 4 pCi/L (148 Bq/m3) for indoor radon concentration in U.S. homes in the interests ofprotection of population health. The World Health Organization has recently established a slightly lowerguideline of 100 Bq/m3.Radon has also been found in natural gas mined in shale fields in Pennsylvania, which is transported bypipeline to New York City, where it is used for cooking in natural gas stoves. This report evaluates theincremental lung cancer risks associated with the presence of radon in natural gas in homes in New YorkState.Radon and Lung CancerRadon is a radioactive gas that originates from the decay of uranium and thorium naturally occurring insoils and rocks. Radon emanates from the earth and tends to accumulate in enclosed spaces, such asunderground mines and houses. The most important radioactive isotope of radon is 222Rn with a half-lifeof 3.8 days (WHO, 2009).When inhaled, alpha particles emitted by its short-lived decay products interact with epithelial cells inthe lung and produce DNA damage. DNA damage in lung epithelial cells may be the first step in a chainof molecular and cellular events that lead to lung cancer (NRC, 1999).The association between exposure to radon and the risk of lung cancer is well established inexperimental animal and human studies (IARC, 1988; IARC, 2001). The evidence for humans initiallycame from a series of cohorts of underground miners exposed in the past to high levels of radon. Thesestudies, conducted in many countries around the world, consistently demonstrated elevated mortalityfrom lung cancer due to occupational radon exposure (Lubin et al, 1995b; NRC, 1999).To increase the statistical power in quantifying the lung cancer mortality risk, data from individualcohort studies were pooled for joint estimation of risk and evaluation of modifying factors. The firstpooled analysis of three studies was performed by the Committee on the Biological Effects of IonizingRadiation (BEIR) within the US National Research Council (NRC, 1988). Later, Lubin et al. (Lubin et al,1995a; Lubin et al, 1995b) pooled data on 65,000 miners and on more than 2,700 lung cancer deathsfrom 11 miner cohorts; this analysis demonstrated a linear dose-response in the range of minerexposures, including lower levels that could be encountered in some homes (Lubin et al, 1995b).Increases in mortality rates from cancers of the stomach and liver and from leukemia (as compared tothe rates in the general population) were demonstrated in this combined miner cohort by Darby and co-workers (Darby et al, 1995). However, for none of these malignancies was mortality associated withcumulative exposure to radon, and it was concluded that these associations were unlikely to be causal(Darby et al, 1995).July 4, 2012 Page 3
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasMore recent analyses of data from miner cohorts confirmed the association between radon exposureand lung cancer risk (Grosche et al, 2006; Tomasek et al, 2008; Vacquier et al, 2009). Some recentstudies suggest that miners may be at increased risk of malignancies other than lung cancer, inparticular leukemia (Kreuzer et al, 2008; Mohner et al, 2006; Rericha et al, 2006; Tomasek & Zarska,2004). However, the evidence for an association between the observed increases and radon exposure isneither consistent nor strong.The NRC Committee on the Biological Effects of Ionizing Radiation (NRC, 1999) employed statisticalmodels developed on the basis of the pooled miner data and extrapolated the risks of lung cancers fromhigh levels of radon experienced in mines to much lower levels characteristic of residential exposures.These extrapolations were based on the US population and lung cancer mortality statistics, residentialradon measurement data, and on available information regarding mechanistic aspects of radiation-induced lung cancer. Using two preferred statistical models (exposure-age-concentration and exposure-age-duration), the Committee estimated the attributable risk (AR) of lung cancer due to residentialradon as 10%-15%, depending on the model. According to the Committee’s estimate, residential radonexposure resulted in between 15,000 and 22,000 lung cancer deaths in the US in 1995.The Committee considered numerous uncertainties in their risk projections, including uncertainties inthe models and in the data used as the basis for these projections. Extrapolations from occupational toresidential settings are complicated by other factors, among them potential confounding by exposuresto lung carcinogens other than radon in mines, potential differences between miners and the generalpopulation in breathing characteristics and smoking habits. For these reasons, it is important to considerdirect observations in the general population.An extensive set of case-control studies of residential radon and lung cancer has been undertaken.Because of the difficulty in identifying small relative risks associated with residential radon exposure,individual studies did not provide conclusive evidence of a link between indoor radon exposure and lungcancer. In order to achieve greater statistical power, combined analysis of residential radon studies havebeen undertaken in North America, Europe and China.A combined analysis of seven North American case-control studies that included 3,662 cases and 4,966controls demonstrated an increase in the odds ratios (ORs) for lung cancer with increasing radonconcentration (Krewski et al, 2005). The estimated excess odds ratio after exposure to radon at aconcentration of 100 Bq/m3 in the exposure time window 5 to 30 years before the index date was 0.11(95% CI: 0.00–0.28). This estimate is compatible with that of 0.12 (0.02–0.25) predicted by downwardextrapolations of the miner data (Krewski et al, 2005). The excess OR was 0.18 (95% CI: 0.02– 0.43) forsubjects who had resided in only one or two houses with at least 20 years of coverage by monitoring.An analysis of data on 7,148 cases of lung cancer and 14,208 controls from 13 European case-controlstudies (Darby et al, 2005) showed an increasing trend in the relative risk of lung cancer with increasingcategory of residential radon concentration. The excess relative risk for a 100 Bq/m3 increase in radonconcentration was 0.08 (95 CI: 0.03-0.16). Adjustment for uncertainties in measured radonconcentrations resulted in a slight increase in the relative risk: 0.16 (95% CI: 0.05-0.31).July 4, 2012 Page 4
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasA pooled analysis of 1050 lung cancer cases and 1996 controls from two large Chinese case-controlstudies (Lubin et al, 2004) produced an excess OR of 0.13 (95% CI: 0.01, 0.36) at radon exposure levels of100 Bq/m3. For subjects who lived in a home for 30 years or more, the excess OR at 100 Bq/m 3 was 0.32(0.07, 0.91).Thus, the estimates of lung cancer risk obtained in the three pooled case-control studies of residentialradon are very similar.Recently, the findings of the case-control studies were confirmed in a large-scale cohort study (Turner etal, 2011). The American Cancer Society Cancer Prevention Study-II is a cohort of about 1.2 millionparticipants with county-level residential radon concentrations and individual-level data on other riskfactors for lung cancer, such as active and passive smoking and occupational exposures to potential lungcarcinogens. Air pollution was estimated from data on ambient sulfate obtained from 149 U.S.metropolitan statistical areas. The analysis included about 812,000 participants with completeinformation on all variables, and nearly 3,500 lung cancer deaths that occurred during six years offollow-up. There was a significant positive linear association between categories of radonconcentrations and lung cancer mortality. The excess relative risk of 0.15 (95% CI 0.01-0.31) per 100Bq/m3 radon concentration was very similar to the lung cancer relative risk estimates obtained in thecase-control studies.In summary, the results of well-designed large-scale epidemiological studies consistently demonstrate astatistically significant positive association between residential radon concentrations and lung cancerrisk, with point estimates of an increase per 100 Bq/m3 ranging from 8% to 32% (Table 1). Thesefindings are consistent with risk projections based on underground miner data.July 4, 2012 Page 5
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasTable 1. Risk Coefficients from Population-Based Studies of Radon and Lung Cancer. Coefficient Study (% increase in lung cancer risk per 100 Bq/m3)Combined analysis of studies of underground 12miners (NRC, 1999)Combined analysis of North American case-controlstudies (Krewski et al., 2005, 2006)  All data 11  Data restricted to best dosimetry 17Combined analysis of 13 European case-controlstudies (Darby et al., 2005)  Unadjusted 8  Adjusted for measurement error 16Combined analysis of two Chinese case-controlstudies (Lubin et al., 2004)  Unadjusted 13  Adjusted for measurement error 32The American Cancer Society Cancer Prevention II 15Survey (Turner et al., 2011)July 4, 2012 Page 6
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas 2. Risk Assessment – Base Case ScenarioThe sequence of steps involved in deriving an estimate of the lifetime lung cancer risk associated withradon in natural gas used for cooking is described in Figure 1. The overall approach is to construct a basecase exposure estimate. In a subsequent section, various additional factors which determine thevariability in exposure that is to be expected are described and their effects on the exposure estimateare quantified as they relate to the final estimate of both exposure and risk of cancer.The risk calculations that have been selected for this analysis require an estimate of exposure in theform of an incremental increase in the time-weighted average exposure to radon gas in units ofBecquerel (Bq) per cubic meter (m3), or Bq/m3.The base case exposure estimate is constructed from a series of measurements and calculations. Thebase case calculations take the following exposure factors into account: a) the concentration of radon in the natural gas in the pipeline that transfers the natural gas from processing facilities to the consumer, b) the amount of natural gas that is used for cooking in a typical residential situation, c) the amount of dilution in the concentration of radon that is expected when the radon is mixed with the indoor air based on the size of the residence and the amount of ventilation the home experiences.The net result of these calculations is to generate an estimate of the incremental average concentrationof radon in the home over time that is contributed by cooking with natural gas. This incremental averageconcentration becomes the measure of exposure for use in the exposure-response calculations whichfollow, to estimate the increased risk of lung cancer associated with this exposure.Concentration of Radon in Natural Gas in the PipelineBased on data provided by Bowser Morner (2012) with measurements taken in late June and early Julyof 2012, we observe a range of radon concentrations in the dry natural gas of approximately 16.9 pCi/Lto 44.1 pCi/L. The concentration of radon decreases as it travels through the pipeline network as aconsequence of radioactive decay such that measurements are expected to be higher closer to thesource of the natural gas and lower for consumers at greater distance from the source. For the basecase analysis, we have chosen 17 pCi/L, a measurement of radon concentration in dry natural gas closestto New York State.July 4, 2012 Page 7
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasFigure 1. Illustration of Sequence of Calculations Resulting in Estimate of Excess Lifetime Risk of Lung Cancer due to Use of Natural Gas in Residential Cooking.July 4, 2012 Page 8
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasUse of Natural Gas for CookingIn this assessment, we focus on the use of natural gas for cooking and, to a limited extent, potentialexposure from pilot lights used in some natural gas water heaters. (At present, there is a trend towardsthe use of electronic ignition as a replacement for pilot lights.) We have not considered radon gas thatenters the home via heating equipment since the gases are expected to be vented to the outside. Fornatural gas water heaters, while the burner is engaged, the gases are expected to be vented eitherthrough natural draft associated with the heat of the combustion products or through power venting.We do consider the potential for exposure to gas consumed by the pilot light of a water heater underthe assumption that during the period when the burner is not engaged, there will be insufficient ventingof the gas. We have not considered natural gas use in unvented space heaters due to the limited use inresidential settings.We have made certain assumptions regarding the amount of use of natural gas, based on the use ofpilot lights, stovetop burners and natural gas ovens. The consumption of gas per hour of use atmaximum output (BTU/hour) is listed in the table below.Table 2. Assumptions Regarding Maximum Energy Output of Various Natural Gas Consuming Devices. Device BTU/hourStovetop burner 4,000Natural gas oven 10,000Stovetop pilot lights (4) 2,000Water heater pilot light 500The assumed number of hours of use per day of each source is provided in the table below. We haveassigned a value of zero for use of a natural gas water heater in the base case because many dwellings(such as apartments) will not have such a device. If the dwelling does have a natural gas water heater, itmay have electronic ignition or adequate venting.July 4, 2012 Page 9
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasTable 3. Base Case Assumptions for Duration of Device Use. Duration of Use Device (hours)Stovetop burner 2Natural gas oven 1Stovetop pilot lights (4) 24Water heater pilot light 0Based on the energy density of natural gas (35.3 BTU/L of NG), the amount of gas consumed by eachdevice per day can be calculated (Table 4).Table 4. Amount of Natural Gas Consumed Per Day – Base Case. Gas Consumed Device (L/day)Stovetop burner 227Natural gas oven 283Stovetop pilot lights (4) 1360Water heater pilot light 0Total 1,870This provides an estimate of the total amount of natural gas used for cooking in a typical day, which canbe divided by 24 hours to give an hourly estimate of natural gas influx due to cooking. The averagenatural gas influx per hour (L/hour) is multiplied by assumed concentration of radon in natural gas (17pCi/L) to provide an estimate of 1,324 pCi/hour.Dilution and VentilationThe radon gas that enters the residential air space through the device uses described above is notcombusted by the flames, since radon is an inert gas. This gas will rapidly diffuse in the home and bediluted by the air within the residence, and further diluted by external air that continuously enters thehome through exchange with the ambient atmosphere.July 4, 2012 Page 10
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasFor the base case scenario, we have assumed a residence of 800 square feet, with 8-foot ceilingsyielding a residential volume of 6,400 cubic feet. We have further assumed a ventilation rate of 0.7 airchanges per hour (ACH).The combination of the size of the residence (181,200 L) and the ventilation rate (0.7 hours-1) yields adilution rate of approximately 126,900 L/hour. When combining the radon influx with the dilution rate,the incremental radon concentration due to natural gas devices used in cooking is estimated to beapproximately 0.01 pCi/L in the base case scenario. For the purposes of compatibility with the dose-response assessment described below, this radon concentration is converted to the units of Bq/m 3 (1pCi/L = 37 Bq/m3), yielding an estimate of incremental radon concentration of 0.386 Bq/m3.Adjustment for Residential OccupancyTo account for the fact that the exposed persons will not spend all of their time within the residence, aresidential occupancy fraction is employed to adjust the daily average exposure estimate. In the basecase scenario, we employ an occupancy fraction of 0.7 (EPA, 2003; NRC, 1999). This yields an occupancy-adjusted radon exposure of 0.270 Bq/m3.Risk CoefficientAn estimate of the annual lung cancer risk associated with radon present in natural gas used for cookingin the home environment is obtained by multiplying the occupancy-adjusted concentration of radon inthe home by an appropriate risk coefficient. As indicated in Table 1, the risk coefficients derived fromdifferent population-based studies on radon and lung cancer are remarkably consistent, with mostfalling in a range of about 10-20% excess risk per 100 Bq/m3 increase in radon concentration. Becausethe objective is to estimate lung cancer risk associated with radon in homes originating from the use ofnatural gas, epidemiologic studies focusing on residential radon exposures are more relevant for riskestimation than those based on occupational studies.The annual incidence of lung cancer is estimated by dividing the number of lung cancer cases (13,468 in2008; CDC, 2012) by the population size (19,490,297 in 2008; US Census Bureau, 2012) for the state ofNew York. This yields an annual lung cancer incidence in New York State of approximately 69.1 per100,000 population (6.91 x 10-4). Multiplying this value by an intermediate excess risk coefficient of 15%per 100 Bq/m3 (the value obtained in the most recent study of radon and lung cancer conducted byTurner et al., 2011) and the estimated incremental radon concentration from natural gas of 0.270 Bq/m 3yields an annual lung cancer risk of 2.8 x 10-7. An estimate of the lifetime lung cancer risk is thenobtained by multiplying the annual risk by 70. This approach yields an estimate of the lifetime excesslung cancer risk from radon present in natural gas used for cooking of 1.96 x 10-5.July 4, 2012 Page 11
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas 3. Sensitivity AnalysisIn order to evaluate the range of exposure to radon from natural gas under different conditions, weconducted a series of sensitivity analyses representing plausible departures from the base case scenario.The results of the sensitivity analysis are included below in Table 5. For each variation from the basecase scenario, the adjusted assumption and its corresponding exposure and risk estimate arehighlighted.Specifically, we examined the impact of different assumptions regarding: a) the level of radon present innatural gas entering the home, b) the level of intensity of use of gas stoves for cooking and natural gashot water heaters, c) the size of the residence, d) the extent of ventilation within the home, and e) thefraction of time spent in the home by the residents.We also explore the use of alternate risk coefficients relating lung cancer risk and residential radon thathave been reported in the literature.Level of Radon in Natural GasThe measurement of radon concentration in natural gas is subject to measurement uncertainty. Theanalytical laboratory provided an upper confidence limit of 20 pCi/L for the measurement whose bestestimate was 17 pCi/L. We have included 20 pCi/L as one alternate scenario.The level of radon in natural gas in many consumer homes will be reduced below 17 pCi/L by the naturalradioactive decay of radon during the time it takes to transmit the gas from the source to the consumerpoint of use. (The value of 17 pCi/L is based on the natural gas measurement closest to New York Cityavailable to us.)Intensity of Use of Gas Stoves and Use of Natural Gas Water HeatersWe explored the sensitivity of the risk estimates to variations in the intensity of use of the natural gasstove for cooking. Intense use is characterized by multiplying the duration of use by a factor of 2.We explored the potential for exposure to natural gas in the dwelling from pilot light use in natural gaswater heaters. The assumption is based on the lack of venting of pilot light gas when the water heaterburner is not engaged and providing sufficient heat to vent the combustion gases. This scenario isdescribed by assuming 24 hours of pilot light use. A further scenario combines intense use with thepresence of an unventilated pilot light in a natural gas water heater.Size of ResidenceTo explore the impact of the volume of the residential dwelling, a series of square footage assumptionswere employed, ranging from a 600 square foot studio apartment to a 2000 square foot home. Aconstant assumption of 8-foot ceilings was employed.July 4, 2012 Page 12
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasExtent of VentilationThe range of ventilation rates was explored using air change rates of 0.5 and 1.0 air changes per hour.An additional scenario using 4.0 air changes per hour was constructed to represent the effect of astovetop vent to the exterior of the residence employed during stove-top cooking and oven use.Occupancy FractionThe variability in the duration of time spent in the residence was explored by including a scenario with100% occupancy of the residence.Risk CoefficientsWe have used lower and upper bounds on the risk coefficient of 10% and 20% to take into accountsampling error in the epidemiologic data on which these estimates are based.Combined Sensitivity AnalysesIn addition to varying each of the above parameters one at a time, we also constructed plausibleminimal and maximal exposure scenarios that involved varying all of these parameters simultaneously.Ideally, simultaneous sensitivity analyses would be conducted based on the multivariate distribution ofthe parameters; since this distribution is not known, we constructed plausible scenarios intended torepresent reasonable minimal and maximal exposure conditions.The proportion of residences that would experience the minimal and maximal exposures described inthe combined sensitivity analyses is unknown, but is likely to be small because of the low probability ofany given household demonstrating the most conservative values of all of the parameters considered inthe combined sensitivity analyses. It would be inappropriate to apply the lifetime excess risk associatedwith either of these scenarios to the entire population of New York State.Results of Sensitivity AnalysisThe results of the sensitivity analysis are summarized in Table 5.Errors associated with the measurement of radon in natural gas have little impact on the estimatedlifetime lung cancer risk, increasing the risk for the base case scenario from 1.96 x 10-5 to 2.31 x 10-5.Increasing the intensity of cooking also has a modest impact on lung cancer risk, as does theconsideration of the pilot light on a hot water heater as an additional source of natural gas entering thehome.Increasing the size of the residence decreases the concentration of indoor radon from natural gas, withthe base case lung cancer risk of 1.96 x 10-5 for an 800 square foot home with 8-foot ceilings decreasingto 0.78 x 10-5 for a 2000 square foot home. For a smaller home of 600 square feet, the lifetime lungcancer risk is increased to 2.62 x 10-5, as compared to the base case scenario.July 4, 2012 Page 13
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasVentilation rate has a similar impact on risk. Increasing the ventilation rate to 4.0 air changes per hour (ascenario designed to represent the use of direct venting of the kitchen air during cooking) reduces thebase case risk to 0.34 x 10-5; a more limited ventilation rate of 0.5 ACH results in a lifetime risk of 2.75 x10-5.Increasing the occupancy fraction from 70% in the base case scenario to the maximum possible value of100% increases the lifetime lung cancer risk from 1.96 x 10-5 to 2.80 x 10-5.Varying the risk coefficient between 10% and 20% has limited impact on cancer risk. At 10% excessrelative risk, the lifetime lung cancer risk is reduced 1.31 x 10-5; at 20%, the risk is increase to 2.62 x 10-5.In the final sensitivity analysis, multiple parameters were varied to represent plausible minimal andmaximal exposure conditions. In the minimal exposure scenario, lifetime cancer risk was estimated to be0.08 x 10-5; in the maximal exposure scenario, lifetime cancer risk was 8.95 x 10-5.July 4, 2012 Page 14
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas Table 5. Sensitivity Analysis Demonstrating Variability in Exposure and Risk Estimates. Point of Entry of Gas into House Occupancy- Excess Stove Use Water Size adjusted Excess Lifetime Level of Lung Exposure Scenario Radon Pilot Gas Heater of Ventilation Occupancy Indoor Radon Risk Cancer in Natural Coefficient Gas Light Burner Oven Pilot Light Residence Rate Fraction Concentration Risk (per 100 3 3 -5 (pCi/L) (h/d) (h/d) (sq. ft.) (ACH) (%) (Bq/m ) Bq/m ) (x10 )Base Case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96Level of Radon in Natural Gas Base case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 Adjusted for measurement error 20 24 2 1 0 800 0.7 70% 0.318 15% 2.31Source of Radon Base case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 Including water heater 17 24 2 1 24 800 0.7 70% 0.320 15% 2.32 Intense cooking 17 24 4 2 0 800 0.7 70% 0.344 15% 2.50 Water heater + intense cooking 17 24 4 2 24 800 0.7 70% 0.393 15% 2.85Size of Residence Very small (studio) 17 24 2 1 0 600 0.7 70% 0.361 15% 2.62 Base case (one bedroom) 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 Two bedrooms 17 24 2 1 0 1000 0.7 70% 0.216 15% 1.57 Three bedrooms 17 24 2 1 0 1200 0.7 70% 0.180 15% 1.31 Large home 17 24 2 1 0 2000 0.7 70% 0.108 15% 0.78Ventilation Rate Limited 17 24 2 1 0 800 0.5 70% 0.379 15% 2.75 Base case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 Increased ventilation 17 24 2 1 0 800 1.0 70% 0.189 15% 1.37 Maximum ventilation 17 24 2 1 0 800 4.0 70% 0.047 15% 0.34Occupancy Fraction Base case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 Maximal occupancy 17 24 2 1 0 800 0.7 100% 0.386 15% 2.80 July 4, 2012 Page 15
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasRisk Coefficient Low estimate 17 24 2 1 0 800 0.7 70% 0.270 10% 1.31 Base case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 High estimate 17 24 2 1 0 800 0.7 70% 0.270 20% 2.62Combined Sensitivity Analysis Plausible minimal exposure 17 24 1 0.5 0 2000 4.0 50% 0.012 15% 0.08 Base case 17 24 2 1 0 800 0.7 70% 0.270 15% 1.96 Plausible maximal exposure 20 24 4 2 24 600 0.5 100% 1.234 15% 8.95 July 4, 2012 Page 16
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas 4. ReferencesBowser Morner (2012). Personal Communication. July 2, 2012Centers for Disease Control and Prevention (2012). http://apps.nccd.cdc.gov/uscs/cancersbystateandregion.aspx. Accessed July 3, 2012.Darby,S., Hill,D., Auvinen,A., Barros-Dios,J.M., Baysson,H., Bochicchio,F., Deo,H., Falk,R., Forastiere,F., Hakama,M., Heid,I., Kreienbrock,L., Kreuzer,M., Lagarde,F., Makelainen,I., Muirhead,C., Oberaigner,W., Pershagen,G., Ruano-Ravina,A., Ruosteenoja,E., Rosario,A.S., Tirmarche,M., Tomasek,L., Whitley,E., Wichmann,H.E., & Doll,R. (2005) Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ., 330, 223.Darby,S.C., Whitley,E., Howe,G.R., Hutchings,S.J., Kusiak,R.A., Lubin,J.H., Morrison,H.I., Tirmarche,M., Tomasek,L., Radford,E.P., & . (1995) Radon and cancers other than lung cancer in underground miners: a collaborative analysis of 11 studies. J Natl.Cancer Inst., 87, 378-384.EPA. EPA Assessment of Risks from Radon in Homes. EPA 402-R-03-003. 2003.Grosche,B., Kreuzer,M., Kreisheimer,M., Schnelzer,M., & Tschense,A. (2006) Lung cancer risk among German male uranium miners: a cohort study, 1946-1998. Br.J Cancer, 95, 1280-1287.IARC (1988) IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 43, Man-made Mineral Fibres and Radon.IARC (2001) IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 78, Ionizing Radiation Part 2: Some Internally Deposited Radionuclides.Kreuzer,M., Walsh,L., Schnelzer,M., Tschense,A., & Grosche,B. (2008) Radon and risk of extrapulmonary cancers: results of the German uranium miners cohort study, 1960-2003. Br.J Cancer, 99, 1946- 1953.Krewski,D., Lubin,J.H., Zielinski,J.M., Alavanja,M., Catalan,V.S., Field,R.W., Klotz,J.B., Letourneau,E.G., Lynch,C.F., Lyon,J.I., Sandler,D.P., Schoenberg,J.B., Steck,D.J., Stolwijk,J.A., Weinberg,C., & Wilcox,H.B. (2005) Residential radon and risk of lung cancer: a combined analysis of 7 North American case-control studies. Epidemiology., 16, 137-145.Krewski,D., Lubin,J.H., Zielinski,J.M., Alavanja,M., Catalan,V.S., Field,R.W., Klotz,J.B., Letourneau,E.G., Lynch,C.F., Lyon,J.L., Sandler,D.P., Schoenberg,J.B., Steck,D.J., Stolwijk,J.A., Weinberg,C., & Wilcox,H.B. (2006) A combined analysis of North American case-control studies of residential radon and lung cancer. J Toxicol Environ Health A., 69, 533-597.Lubin,J.H., Boice,J.D., Jr., Edling,C., Hornung,R.W., Howe,G., Kunz,E., Kusiak,R.A., Morrison,H.I., Radford,E.P., Samet,J.M., & . (1995a) Radon-exposed underground miners and inverse dose-rate (protraction enhancement) effects. Health Phys., 69, 494-500.July 4, 2012 Page 17
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasLubin,J.H., Boice,J.D., Jr., Edling,C., Hornung,R.W., Howe,G.R., Kunz,E., Kusiak,R.A., Morrison,H.I., Radford,E.P., Samet,J.M., & . (1995b) Lung cancer in radon-exposed miners and estimation of risk from indoor exposure. J Natl.Cancer Inst., 87, 817-827.Lubin,J.H., Wang,Z.Y., Boice,J.D., Jr., Xu,Z.Y., Blot,W.J., De,W.L., & Kleinerman,R.A. (2004) Risk of lung cancer and residential radon in China: pooled results of two studies. Int.J Cancer, 109, 132-137.Mohner,M., Lindtner,M., Otten,H., & Gille,H.G. (2006) Leukemia and exposure to ionizing radiation among German uranium miners. Am.J Ind.Med., 49, 238-248.NRC (1988) Committee on Health Risks of Exposure to Radon (BEIR IV). Health Risks of Radon and Other Internally Deposited Alpha-Emitters.NRC (1999) Committee on Health Risks of Exposure to Radon (BEIR VI). Health Effects of Exposure to Radon, National Academy Press, Washington, D.C.Rericha,V., Kulich,M., Rericha,R., Shore,D.L., & Sandler,D.P. (2006) Incidence of leukemia, lymphoma, and multiple myeloma in Czech uranium miners: a case-cohort study. Environ Health Perspect., 114, 818-822.Tomasek,L., Rogel,A., Tirmarche,M., Mitton,N., & Laurier,D. (2008) Lung cancer in French and Czech uranium miners: Radon-associated risk at low exposure rates and modifying effects of time since exposure and age at exposure. Radiat.Res., 169, 125-137.Tomasek,L. & Zarska,H. (2004) Lung cancer risk among Czech tin and uranium miners--comparison of lifetime detriment. Neoplasma., 51, 255-260.Turner,M.C., Krewski,D., Chen,Y., Pope,C.A., III, Gapstur,S., & Thun,M.J. (2011) Radon and lung cancer in the American Cancer Society cohort. Cancer Epidemiol.Biomarkers.Prev., 20, 438-448.United States Census Bureau (2008). http://www.census.gov/popest/data/historical/2000s/vintage_2008/index.html. Accessed July 3, 2012.Vacquier,B., Rogel,A., Leuraud,K., Caer,S., Acker,A., & Laurier,D. (2009) Radon-associated lung cancer risk among French uranium miners: modifying factors of the exposure-risk relationship. Radiat.Environ Biophys., 48, 1-9.WHO (2009) WHO Handbook on Indoor Radon: a Public Health Perspective. WHO Geneva.July 4, 2012 Page 18
    • Assessment of Lung Cancer Risk Associated with Radon in Natural Gas 5. ContributorsThe following individuals contributed to the development of this report.Mr. Ahmed Almaskut, Risk Analyst, RSI. Mr. Almaskut is a quantitative risk analyst with expertise incalculation of environmental burden of disease. Mr. Almaskut is experienced in the application of riskmodels for the estimation of environmental health risks, including those associated with ambient airpollution and environmental radon.Dr. Mustafa Al-Zoughool, Research Scientist, McLaughlin Centre for Population Health Risk Assessment,University of Ottawa. Dr. Al-Zoughool is currently working as a cancer epidemiologist with theMcLaughlin Centre and has completed several projects with RSI relating to cancer epidemiology. Dr. Al-Zoughool completed a postdoctoral fellowship at IARC, after earning his PhD in Molecular Toxicologyfrom the University of Cincinnati, Ohio.Dr. Douglas Chambers, Director of Risk and Radioactivity Studies, SENES Consultants. Dr. Chambers hasover 25 years of expertise in environmental radioactivity and risk assessment. Dr. Chambers is aphysicist with particular expertise in radon dosimetry and exposure assessment. He was lead author onthe 2006 UNSCEAR report on radon.Dr. Phil Hopke, Bayard D. Clarkson Distinguished Professor, Clarkson University. Dr. Hopke, an expert inradon dosimetry, was a member of the BEIR VI Committee, which conducted a comprehensiveevaluation of the health risks of radon in U.S. homes. Dr. Hopke is Director of the Institute for aSustainable Environment and Director for the Center for Air Resources Engineering and Science atClarkson.Dr. Daniel Krewski, Chief Risk Scientist and CEO, RSI. Dr. Krewski has extensive experience in theassessment and management of population health risks, including those associated with environmentalradon. He was a member of the US National Research Council BIER VI and BIER VII Committees, and haspreviously served for six years on the NRC Nuclear and Radiation Studies Board. Dr. Krewski holds aNatural Sciences and Engineering Research Council of Canada Chair in Risk Science at the University ofOttawa.Dr. Ernest Letourneau, Health Canada (Retired). While with Health Canada, Dr. Letourneau served asDirector of the Radiation Protection Bureau, which includes responsibility for the assessment andmanagement of ionizing and non-ionizing radiation. Dr. Letourneau has extensive experience withinternational agencies focusing on radiation risk assessment, and conducted a large case control studyof residential radon and lung cancer in Winnipeg, Manitoba.Dr. Don Mattison, Chief Medical Officer, RSI. Dr. Mattison’s career has included previous positions asSenior Advisor to the Director of the Eunice Kennedy Shriver National Institute of Child Health andHuman Development, Medical Director of the March of Dimes; Dean of the Graduate School of PublicHealth at the University of Pittsburgh, Professor of Obstetrics and Gynecology and InterdisciplinaryJuly 4, 2012 Page 19
    • Assessment of Lung Cancer Risk Associated with Radon in Natural GasToxicology at the University of Arkansas for Medical Sciences, and Director of Human Risk Assessment atthe FDA National Center for Toxicological Research.Mr. Greg Paoli, Chief Operating Officer and Principal Risk Scientist, RSI. Greg Paoli serves as PrincipalRisk Scientist at Risk Sciences International, a consulting firm specializing in risk assessment,management and communication in the field of public health, safety and risk-based decision-support. He specializes in probabilistic risk assessment methods, the development of risk-baseddecision-support tools and comparative risk assessment. Mr. Paoli has served on a number of expertcommittees devoted to the risk sciences. He was a member of the U.S. National Research Councilcommittee that issued the 2009 report, Science and Decisions: Advancing Risk Assessment.Dr. Natasha Shilnikova, Senior Health Risk Analyst, RSI. Dr. Shilnikova has over 25 years of expertiseworking in the fields of epidemiology and radiation. Dr. Shilnikova has worked on many projects throughRSI and the University of Ottawa relating to cancer epidemiology and population health. She earned aPhD equivalent in Medical Sciences and a Doctorate of Medicine equivalent with specialization inEpidemiology and Hygiene.July 4, 2012 Page 20