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Radon Testing in Households With a Residential SMOKER

August 13, 1999 / 48(31);683-686 Radon Testing in Households with a Residential
Smoker -- United States, 1993-1994 Epidemiologic investigations of underground
miners (1) and studies of alpha particle carcinogenesis among laboratory animals
(2) suggest that exposure to the radioactive decay products (progeny) of radon
is an important risk factor for lung cancer. Persons who smoke cigarettes and
are exposed to these radon progeny have a substantially greater risk for developing
malignancy than nonsmokers (3). Residential radon concentrations above the U.S.
Environmental Protection Agency's (EPA) action level of 4 pCi/L are the primary
sources of exposure among the general population (4). EPA and the Public Health
Service promote home testing for radon, especially in households with a person
who smokes. However, it is unknown whether households that contain smokers are
more likely than those without smokers to test for radon. To characterize radon
testing practices of households that contain a person who smokes within the dwelling
(i.e., residential smoker), CDC analyzed survey data from the National Health
Interview Survey (NHIS). This report summarizes the results of this analysis,
which indicates that households with a residential smoker are significantly less
likely to test for radon than those without smokers.

NHIS collects information on various health issues using an annual probability
sample that is representative of the civilian, noninstitutionalized population
of the United States. Radon testing and radon awareness data were collected
through a personal interview with one randomly selected adult (aged greater
than or equal to 18 years) per household as part of the NHIS Year 2000 Supplements
during 1990, 1991, 1993, and 1994. For this investigation, data from the 1993
and 1994 NHIS Year 2000 Supplements were combined and merged with the 1993 and
1994 NHIS household records to allow analysis at the household level (n=40,766).
The results presented in this report are the mean values for the 1993 and 1994
NHIS Year 2000 Supplements combined. Response rates for the two survey years
were 81.2% and 79.5%, respectively.

Radon testing data were derived from responses to the question "Has your
household air been tested for the presence of radon?" Data representing
the presence of a residential smoker were derived from responses to the question
"Does anyone who lives here smoke cigarettes, cigars, or pipes anywhere
inside this home?" Trailer homes and mobile homes and apartments or condominiums
above the second floor were excluded (n=5801) because of their negligible radon
exposure risk. A total of 34,965 households were considered at-risk for radon

The NHIS radon testing question was asked only of households that reported
knowledge of radon. However, assuming that households without knowledge of radon
did not have their residences tested, it is possible to calculate radon testing
estimates for all households. This analysis included all households; however,
it also provides radon testing estimates restricted to households with knowledge
of radon, for comparison. The analyses for all households and households with
knowledge of radon were calculated using SUDAAN and were weighted to produce
national estimates.

During 1993-1994, an overall mean of 5.5 million (6.7%) households tested for
radon (Table 1). This number of households included approximately 11.7 million

Households that contained a residential smoker were significantly less likely
to have tested for radon than households that did not contain a residential
smoker (5.9% versus 7.1%, respectively). Differences were significant for the
crude association (odds ratio [OR]=0.81; 95% confidence interval [CI]=0.74-0.90)
and when controlling for household level of education, poverty status, geographic
region, residence location, and presence of children (adjusted OR=0.88; 95%

When the analysis was restricted to households that reported knowledge of radon
(n=24,782), the percentage of households that tested for radon increased to
9.4%. Among households that contained a residential smoker, 8.3% tested for
radon, and among households that did not contain a smoker, 9.8% tested. Differences
were significant for both the crude association (OR=0.83; 95% CI=0.75-0.92)
and when controlling for relevant covariates (adjusted OR=0.87; 95% CI=0.79-0.96).

Reported by: Illness and Disability Statistics Br, Div of Health Interview
Statistics, National Center for Health Statistics, CDC.

Editorial Note: Each year, approximately 10%-14% of lung cancer deaths in the
United States are attributable to indoor radon (5), making residential exposure
the second leading single cause of lung cancer. The risk for malignancy increases
in the presence of cigarette smoking because of a synergistic relation between
indoor radon and cigarette smoking, an effect-modifying association that is
characterized as submultiplicative. Although the biologic basis for the interaction
between cigarette smoking and residential radon is unclear, smoking may promote
radon-initiated cells (6), implying that initial exposure to radon may increase
the susceptibility of lung cells to the harmful effects of smoking.

The Public Health Service and EPA encourage persons to determine their exposure
to residential radon and to reduce high levels, especially in households that
contain persons who smoke. One of the national health objectives for 2000 is
to increase to at least 40% the proportion of homes in which homeowners or occupants
have tested their home for radon and have found either negligible risk or have
modified the dwelling to reduce risk (objective 11.6) (7). In addition, the
objective seeks to increase radon testing to at least 50% in high-risk households
containing cigarette smokers. The findings in this report suggest that these
goals probably will not be met.

The findings in this report are subject to at least three limitations. First,
some respondents might not have been able to recall whether their homes had
been tested for radon, resulting in reporting errors. Second, this investigation
classified the smoking status of the household by asking whether the household
contained a person who smoked within the dwelling; however, it did not assess
whether a household contained a smoker who chose not to use tobacco products
within the dwelling. An estimated 16.3% of adult smokers do not smoke within
their residences (1995-1996 Current Population Survey, unpublished data, 1999).
Identifying smokers who did not smoke in their dwelling would have provided
a more complete picture of household smoking status, but the 1993 and 1994 NHIS
did not allow this analysis. Finally, the analysis was limited to cigarette
smoking, but the NHIS included smokers of all types of tobacco.

Radon testing and mitigation practices need to improve in the United States,
overall and among high-risk households that contain residential smokers. The
most effective means of reducing risk for radon-related lung cancer in these
households is to encourage the smoker to stop using tobacco products (3,8,9).
However, to maximize lung cancer risk reduction, smokers in residences with
high radon concentrations should quit smoking and reduce high radon levels (8).
The National Research Council (5) estimates that eliminating indoor radon exposures
that are in excess of the EPA's action level would prevent approximately 30%
of radon-attributable lung cancer deaths, and of these, 86% would be among persons
who have ever smoked during their lifetimes. The findings in this report underscore
the importance of programmatic efforts aimed at improving radon testing and
mitigation practices, particularly among households that contain a residential

References Lubin JH, Boice JD Jr. Lung cancer risk from residential radon:
meta-analysis of eight epidemiologic studies. J Natl Cancer Inst 1997;89:49-57.
Gilbert ES, Dagle GE, Cross FT. Analysis of lung tumor risks in rats exposed
to radon. Radiat Res 1996;145:350-60. Lubin JH, Steindorf K. Cigarette use and
the estimation of lung cancer attributable to radon in the United States. Radiat
Res 1995;141:79-85. Axelson O. Cancer risks from exposure to radon in homes.
Environ Health Perspect 1995;103: 37-43. National Academy of Sciences. Biological
effects of ionizing radiation (BEIR) VI report: the health effects of exposure
to indoor radon. Executive summary. Available at http://www.epa.gov/iaq/radon/beiriv1.html.
Accessed February 19, 1998. Thomas D, Pogoda J, Langholz B, Mack W. Temporal
modifiers of the radon-smoking interaction. Health Physics 1994;66:257-62. US
Department of Health and Human Services. Healthy people 2000 review, 1997. Hyattsville,
Maryland: US Department of Health and Human Services, 1997. Mendez D, Warner
KE, Courant PN. Effects of radon mitigation vs smoking cessation in reducing
radon-related risk of lung cancer. Am J Public Health 1998;88:811-2. Ford ES,
Kelly AE, Teutsch SM, Thacker SB, Garbe PL. Radon and lung cancer: a cost-effectiveness
analysis. Am J Public Health 1999;89:351-7.

Table 1

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TABLE 1. Weighted percentage of households that tested for radon, by presence
of a person who smokes in the residence (i.e., residential smoker) and selected
household characteristics -- United States, 1993-1994* ==========================================================================================================
Residential smoker No residential smoker Total ------------------- ----------------------
--------------------- Characteristic No.+ % (SE&) No. % (SE) No. % (SE)
Highest level education in the household <High school 67 1.8% (0.3) 133 1.9%
(0.3) 200 1.9% (0.2) High school/General Equivalency Diploma 554 5.4% (0.4)
874 5.2% (0.3) 1428 5.3% (0.2) >High school 826 7.8% (0.5) 3064 9.2% (0.4)
3890 8.8% (0.3)

Household poverty status@ At or above 1280 6.6% (0.3) 3821 7.9% (0.3) 5101
7.6% (0.2) Below 110 3.3% (0.5) 135 2.6% (0.3) 246 2.9% (0.3) Unknown 56 2.9%
(0.6) 124 3.1% (0.4) 180 3.0% (0.4)

Geographic region of household Northeast 445 9.2% (0.6) 1458 13.4% (0.6) 1903
12.1% (0.4) Midwest 491 6.9% (0.5) 1206 8.2% (0.6) 1698 7.8% (0.5) South 346
4.2% (0.4) 895 5.0% (0.3) 1241 4.8% (0.3) West 164 3.7% (0.5) 522 3.7% (0.5)
686 3.7% (0.5)

Household location Urban 1070 5.8% (0.3) 2968 6.9% (0.3) 4038 6.5% (0.2) Rural
377 6.1% (0.6) 1112 8.0% (0.5) 1489 7.4% (0.4)

Children residing in household Yes 608 6.4% (0.5) 1848 9.0% (0.4) 2456 8.2%
(0.4) No 839 5.6% (0.3) 2232 6.0% (0.2) 3071 5.9% (0.2)

Total 1446 5.9% (0.3) 4081 7.1% (0.3) 5527 6.7% (0.2) ----------------------------------------------------------------------------------------------
* This analysis included all households and excluded trailer homes and mobile
homes and apartments and condominiums above the second floor. + Number of households
in thousands. Columns may not add to total because of rounding. & Standard
error. @ Poverty status based on the U.S. Department of Agriculture's economy
food plan. ==========================================================================================================

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