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

FINAL REPORT

An Assessment of the Lung Cancer Risk
Associated with the Presence of Radon in Natural
Gas 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

Contents
1. BACKGROUND ............................................................................................................................................... 3

RADON AND LUNG CANCER ..............................................................................................................................................3

2. 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 .........................................................................................................................................................11

3. 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 ...................................................................................................................................13

4. REFERENCES ................................................................................................................................................ 17

5. CONTRIBUTORS ........................................................................................................................................... 19

July 4, 2012 Page ii


1. Background
Radon is a well-established risk factor for human lung cancer. Because radon released from the earth’s
crust can make its way into the home environment, the U.S. Environmental Protection Agency has set a
guideline of 4 pCi/L (148 Bq/m3) for indoor radon concentration in U.S. homes in the interests of
protection of population health. The World Health Organization has recently established a slightly lower
guideline of 100 Bq/m3.

Radon has also been found in natural gas mined in shale fields in Pennsylvania, which is transported by
pipeline to New York City, where it is used for cooking in natural gas stoves. This report evaluates the
incremental lung cancer risks associated with the presence of radon in natural gas in homes in New York
State.

Radon and Lung Cancer
Radon is a radioactive gas that originates from the decay of uranium and thorium naturally occurring in
soils and rocks. Radon emanates from the earth and tends to accumulate in enclosed spaces, such as
underground mines and houses. The most important radioactive isotope of radon is 222Rn with a half-life
of 3.8 days (WHO, 2009).

When inhaled, alpha particles emitted by its short-lived decay products interact with epithelial cells in
the lung and produce DNA damage. DNA damage in lung epithelial cells may be the first step in a chain
of 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 in
experimental animal and human studies (IARC, 1988; IARC, 2001). The evidence for humans initially
came from a series of cohorts of underground miners exposed in the past to high levels of radon. These
studies, conducted in many countries around the world, consistently demonstrated elevated mortality
from 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 individual
cohort studies were pooled for joint estimation of risk and evaluation of modifying factors. The first
pooled analysis of three studies was performed by the Committee on the Biological Effects of Ionizing
Radiation (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 deaths
from 11 miner cohorts; this analysis demonstrated a linear dose-response in the range of miner
exposures, 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 to
the 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 with
cumulative exposure to radon, and it was concluded that these associations were unlikely to be causal
(Darby et al, 1995).

July 4, 2012 Page 3


More recent analyses of data from miner cohorts confirmed the association between radon exposure
and lung cancer risk (Grosche et al, 2006; Tomasek et al, 2008; Vacquier et al, 2009). Some recent
studies suggest that miners may be at increased risk of malignancies other than lung cancer, in
particular 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 is
neither consistent nor strong.

The NRC Committee on the Biological Effects of Ionizing Radiation (NRC, 1999) employed statistical
models developed on the basis of the pooled miner data and extrapolated the risks of lung cancers from
high 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, residential
radon 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 residential
radon as 10%-15%, depending on the model. According to the Committee’s estimate, residential radon
exposure 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 in
the models and in the data used as the basis for these projections. Extrapolations from occupational to
residential settings are complicated by other factors, among them potential confounding by exposures
to lung carcinogens other than radon in mines, potential differences between miners and the general
population in breathing characteristics and smoking habits. For these reasons, it is important to consider
direct 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 lung
cancer. In order to achieve greater statistical power, combined analysis of residential radon studies have
been undertaken in North America, Europe and China.

A combined analysis of seven North American case-control studies that included 3,662 cases and 4,966
controls demonstrated an increase in the odds ratios (ORs) for lung cancer with increasing radon
concentration (Krewski et al, 2005). The estimated excess odds ratio after exposure to radon at a
concentration 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 downward
extrapolations of the miner data (Krewski et al, 2005). The excess OR was 0.18 (95% CI: 0.02– 0.43) for
subjects 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-control
studies (Darby et al, 2005) showed an increasing trend in the relative risk of lung cancer with increasing
category of residential radon concentration. The excess relative risk for a 100 Bq/m3 increase in radon
concentration was 0.08 (95 CI: 0.03-0.16). Adjustment for uncertainties in measured radon
concentrations resulted in a slight increase in the relative risk: 0.16 (95% CI: 0.05-0.31).

July 4, 2012 Page 4


A pooled analysis of 1050 lung cancer cases and 1996 controls from two large Chinese case-control
studies (Lubin et al, 2004) produced an excess OR of 0.13 (95% CI: 0.01, 0.36) at radon exposure levels of
100 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 residential
radon are very similar.

Recently, the findings of the case-control studies were confirmed in a large-scale cohort study (Turner et
al, 2011). The American Cancer Society Cancer Prevention Study-II is a cohort of about 1.2 million
participants with county-level residential radon concentrations and individual-level data on other risk
factors for lung cancer, such as active and passive smoking and occupational exposures to potential lung
carcinogens. 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 complete
information on all variables, and nearly 3,500 lung cancer deaths that occurred during six years of
follow-up. There was a significant positive linear association between categories of radon
concentrations and lung cancer mortality. The excess relative risk of 0.15 (95% CI 0.01-0.31) per 100
Bq/m3 radon concentration was very similar to the lung cancer relative risk estimates obtained in the
case-control studies.

In summary, the results of well-designed large-scale epidemiological studies consistently demonstrate a
statistically significant positive association between residential radon concentrations and lung cancer
risk, with point estimates of an increase per 100 Bq/m3 ranging from 8% to 32% (Table 1). These
findings are consistent with risk projections based on underground miner data.

July 4, 2012 Page 5


Table 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 12
miners (NRC, 1999)

Combined analysis of North American case-control
studies (Krewski et al., 2005, 2006)

 All data 11
 Data restricted to best dosimetry 17

Combined analysis of 13 European case-control
studies (Darby et al., 2005)

 Unadjusted 8
 Adjusted for measurement error 16

Combined analysis of two Chinese case-control
studies (Lubin et al., 2004)
 Unadjusted 13
 Adjusted for measurement error 32

The American Cancer Society Cancer Prevention II 15
Survey (Turner et al., 2011)

July 4, 2012 Page 6


2. Risk Assessment – Base Case Scenario
The sequence of steps involved in deriving an estimate of the lifetime lung cancer risk associated with
radon in natural gas used for cooking is described in Figure 1. The overall approach is to construct a base
case exposure estimate. In a subsequent section, various additional factors which determine the
variability in exposure that is to be expected are described and their effects on the exposure estimate
are 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 the
form of an incremental increase in the time-weighted average exposure to radon gas in units of
Becquerel (Bq) per cubic meter (m3), or Bq/m3.

The base case exposure estimate is constructed from a series of measurements and calculations. The
base 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 concentration
of radon in the home over time that is contributed by cooking with natural gas. This incremental average
concentration becomes the measure of exposure for use in the exposure-response calculations which
follow, to estimate the increased risk of lung cancer associated with this exposure.

Concentration of Radon in Natural Gas in the Pipeline
Based on data provided by Bowser Morner (2012) with measurements taken in late June and early July
of 2012, we observe a range of radon concentrations in the dry natural gas of approximately 16.9 pCi/L
to 44.1 pCi/L. The concentration of radon decreases as it travels through the pipeline network as a
consequence of radioactive decay such that measurements are expected to be higher closer to the
source of the natural gas and lower for consumers at greater distance from the source. For the base
case analysis, we have chosen 17 pCi/L, a measurement of radon concentration in dry natural gas closest
to New York State.

July 4, 2012 Page 7


Figure 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


Use of Natural Gas for Cooking
In this assessment, we focus on the use of natural gas for cooking and, to a limited extent, potential
exposure from pilot lights used in some natural gas water heaters. (At present, there is a trend towards
the use of electronic ignition as a replacement for pilot lights.) We have not considered radon gas that
enters the home via heating equipment since the gases are expected to be vented to the outside. For
natural gas water heaters, while the burner is engaged, the gases are expected to be vented either
through 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 under
the assumption that during the period when the burner is not engaged, there will be insufficient venting
of the gas. We have not considered natural gas use in unvented space heaters due to the limited use in
residential settings.

We have made certain assumptions regarding the amount of use of natural gas, based on the use of
pilot lights, stovetop burners and natural gas ovens. The consumption of gas per hour of use at
maximum output (BTU/hour) is listed in the table below.

Table 2. Assumptions Regarding Maximum Energy Output of Various Natural Gas Consuming Devices.

Device BTU/hour

Stovetop burner 4,000

Natural gas oven 10,000

Stovetop pilot lights (4) 2,000

Water heater pilot light 500

The assumed number of hours of use per day of each source is provided in the table below. We have
assigned 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, it
may have electronic ignition or adequate venting.

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Table 3. Base Case Assumptions for Duration of Device Use.

Duration of Use
Device
(hours)

Stovetop burner 2

Natural gas oven 1

Stovetop pilot lights (4) 24


Based on the energy density of natural gas (35.3 BTU/L of NG), the amount of gas consumed by each
device 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 227

Natural gas oven 283

Stovetop pilot lights (4) 1360


Total 1,870

This provides an estimate of the total amount of natural gas used for cooking in a typical day, which can
be divided by 24 hours to give an hourly estimate of natural gas influx due to cooking. The average
natural gas influx per hour (L/hour) is multiplied by assumed concentration of radon in natural gas (17
pCi/L) to provide an estimate of 1,324 pCi/hour.

Dilution and Ventilation
The radon gas that enters the residential air space through the device uses described above is not
combusted by the flames, since radon is an inert gas. This gas will rapidly diffuse in the home and be
diluted by the air within the residence, and further diluted by external air that continuously enters the
home through exchange with the ambient atmosphere.

July 4, 2012 Page 10


For the base case scenario, we have assumed a residence of 800 square feet, with 8-foot ceilings
yielding a residential volume of 6,400 cubic feet. We have further assumed a ventilation rate of 0.7 air
changes per hour (ACH).

The combination of the size of the residence (181,200 L) and the ventilation rate (0.7 hours-1) yields a
dilution 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 be
approximately 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 (1
pCi/L = 37 Bq/m3), yielding an estimate of incremental radon concentration of 0.386 Bq/m3.

Adjustment for Residential Occupancy
To account for the fact that the exposed persons will not spend all of their time within the residence, a
residential occupancy fraction is employed to adjust the daily average exposure estimate. In the base
case 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 Coefficient
An estimate of the annual lung cancer risk associated with radon present in natural gas used for cooking
in the home environment is obtained by multiplying the occupancy-adjusted concentration of radon in
the home by an appropriate risk coefficient. As indicated in Table 1, the risk coefficients derived from
different population-based studies on radon and lung cancer are remarkably consistent, with most
falling in a range of about 10-20% excess risk per 100 Bq/m3 increase in radon concentration. Because
the objective is to estimate lung cancer risk associated with radon in homes originating from the use of
natural gas, epidemiologic studies focusing on residential radon exposures are more relevant for risk
estimation than those based on occupational studies.

The annual incidence of lung cancer is estimated by dividing the number of lung cancer cases (13,468 in
2008; CDC, 2012) by the population size (19,490,297 in 2008; US Census Bureau, 2012) for the state of
New York. This yields an annual lung cancer incidence in New York State of approximately 69.1 per
100,000 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 by
Turner et al., 2011) and the estimated incremental radon concentration from natural gas of 0.270 Bq/m 3
yields an annual lung cancer risk of 2.8 x 10-7. An estimate of the lifetime lung cancer risk is then
obtained by multiplying the annual risk by 70. This approach yields an estimate of the lifetime excess
lung cancer risk from radon present in natural gas used for cooking of 1.96 x 10-5.



3. Sensitivity Analysis
In order to evaluate the range of exposure to radon from natural gas under different conditions, we
conducted 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 base
case scenario, the adjusted assumption and its corresponding exposure and risk estimate are
highlighted.

Specifically, we examined the impact of different assumptions regarding: a) the level of radon present in
natural gas entering the home, b) the level of intensity of use of gas stoves for cooking and natural gas
hot water heaters, c) the size of the residence, d) the extent of ventilation within the home, and e) the
fraction 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 that
have been reported in the literature.

Level of Radon in Natural Gas
The measurement of radon concentration in natural gas is subject to measurement uncertainty. The
analytical laboratory provided an upper confidence limit of 20 pCi/L for the measurement whose best
estimate 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 natural
radioactive decay of radon during the time it takes to transmit the gas from the source to the consumer
point of use. (The value of 17 pCi/L is based on the natural gas measurement closest to New York City
available to us.)

Intensity of Use of Gas Stoves and Use of Natural Gas Water Heaters
We explored the sensitivity of the risk estimates to variations in the intensity of use of the natural gas
stove 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 gas
water heaters. The assumption is based on the lack of venting of pilot light gas when the water heater
burner is not engaged and providing sufficient heat to vent the combustion gases. This scenario is
described by assuming 24 hours of pilot light use. A further scenario combines intense use with the
presence of an unventilated pilot light in a natural gas water heater.

Size of Residence
To explore the impact of the volume of the residential dwelling, a series of square footage assumptions
were employed, ranging from a 600 square foot studio apartment to a 2000 square foot home. A
constant assumption of 8-foot ceilings was employed.



Extent of Ventilation
The 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 a
stovetop vent to the exterior of the residence employed during stove-top cooking and oven use.

Occupancy Fraction
The variability in the duration of time spent in the residence was explored by including a scenario with
100% occupancy of the residence.

Risk Coefficients
We have used lower and upper bounds on the risk coefficient of 10% and 20% to take into account
sampling error in the epidemiologic data on which these estimates are based.

Combined Sensitivity Analyses
In addition to varying each of the above parameters one at a time, we also constructed plausible
minimal and maximal exposure scenarios that involved varying all of these parameters simultaneously.
Ideally, simultaneous sensitivity analyses would be conducted based on the multivariate distribution of
the parameters; since this distribution is not known, we constructed plausible scenarios intended to
represent reasonable minimal and maximal exposure conditions.

The proportion of residences that would experience the minimal and maximal exposures described in
the combined sensitivity analyses is unknown, but is likely to be small because of the low probability of
any given household demonstrating the most conservative values of all of the parameters considered in
the combined sensitivity analyses. It would be inappropriate to apply the lifetime excess risk associated
with either of these scenarios to the entire population of New York State.

Results of Sensitivity Analysis
The 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 estimated
lifetime 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 the
consideration of the pilot light on a hot water heater as an additional source of natural gas entering the
home.

Increasing the size of the residence decreases the concentration of indoor radon from natural gas, with
the base case lung cancer risk of 1.96 x 10-5 for an 800 square foot home with 8-foot ceilings decreasing
to 0.78 x 10-5 for a 2000 square foot home. For a smaller home of 600 square feet, the lifetime lung
cancer risk is increased to 2.62 x 10-5, as compared to the base case scenario.



Ventilation rate has a similar impact on risk. Increasing the ventilation rate to 4.0 air changes per hour (a
scenario designed to represent the use of direct venting of the kitchen air during cooking) reduces the
base 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 x
10-5.

Increasing the occupancy fraction from 70% in the base case scenario to the maximum possible value of
100% 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% excess
relative 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 and
maximal exposure conditions. In the minimal exposure scenario, lifetime cancer risk was estimated to be
0.08 x 10-5; in the maximal exposure scenario, lifetime cancer risk was 8.95 x 10-5.



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% 1.96
Level 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% 2.31
Source 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% 2.85
Size 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% 0.78
Ventilation 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% 0.34
Occupancy 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



Risk 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% 2.62
Combined 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



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5. Contributors
The following individuals contributed to the development of this report.

Mr. Ahmed Almaskut, Risk Analyst, RSI. Mr. Almaskut is a quantitative risk analyst with expertise in
calculation of environmental burden of disease. Mr. Almaskut is experienced in the application of risk
models for the estimation of environmental health risks, including those associated with ambient air
pollution 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 the
McLaughlin 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 Toxicology
from the University of Cincinnati, Ohio.

Dr. Douglas Chambers, Director of Risk and Radioactivity Studies, SENES Consultants. Dr. Chambers has
over 25 years of expertise in environmental radioactivity and risk assessment. Dr. Chambers is a
physicist with particular expertise in radon dosimetry and exposure assessment. He was lead author on
the 2006 UNSCEAR report on radon.

Dr. Phil Hopke, Bayard D. Clarkson Distinguished Professor, Clarkson University. Dr. Hopke, an expert in
radon dosimetry, was a member of the BEIR VI Committee, which conducted a comprehensive
evaluation of the health risks of radon in U.S. homes. Dr. Hopke is Director of the Institute for a
Sustainable Environment and Director for the Center for Air Resources Engineering and Science at
Clarkson.

Dr. Daniel Krewski, Chief Risk Scientist and CEO, RSI. Dr. Krewski has extensive experience in the
assessment and management of population health risks, including those associated with environmental
radon. He was a member of the US National Research Council BIER VI and BIER VII Committees, and has
previously served for six years on the NRC Nuclear and Radiation Studies Board. Dr. Krewski holds a
Natural Sciences and Engineering Research Council of Canada Chair in Risk Science at the University of
Ottawa.

Dr. Ernest Letourneau, Health Canada (Retired). While with Health Canada, Dr. Letourneau served as
Director of the Radiation Protection Bureau, which includes responsibility for the assessment and
management of ionizing and non-ionizing radiation. Dr. Letourneau has extensive experience with
international agencies focusing on radiation risk assessment, and conducted a large case control study
of residential radon and lung cancer in Winnipeg, Manitoba.

Dr. Don Mattison, Chief Medical Officer, RSI. Dr. Mattison’s career has included previous positions as
Senior Advisor to the Director of the Eunice Kennedy Shriver National Institute of Child Health and
Human Development, Medical Director of the March of Dimes; Dean of the Graduate School of Public
Health at the University of Pittsburgh, Professor of Obstetrics and Gynecology and Interdisciplinary



Toxicology at the University of Arkansas for Medical Sciences, and Director of Human Risk Assessment at
the FDA National Center for Toxicological Research.

Mr. Greg Paoli, Chief Operating Officer and Principal Risk Scientist, RSI. Greg Paoli serves as Principal
Risk 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-based
decision-support tools and comparative risk assessment. Mr. Paoli has served on a number of expert
committees devoted to the risk sciences. He was a member of the U.S. National Research Council
committee 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 expertise
working in the fields of epidemiology and radiation. Dr. Shilnikova has worked on many projects through
RSI and the University of Ottawa relating to cancer epidemiology and population health. She earned a
PhD equivalent in Medical Sciences and a Doctorate of Medicine equivalent with specialization in
Epidemiology and Hygiene.


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