Gas Exposure and Lung Cancer", American Journal
of Epidemiology, June 2000
R. William Field, Daniel J.
Steck, Brian J. Smith, et al
Female Iowa residents, age 40-84
years, both non-smokers and ever smokers, who had lived
in their current home for at least 20 consecutive years
and completed year-long radon measurements. Included
413 lung cancer cases (86.4% ever smokers) and 614 controls
(32.5% ever smokers).
The Iowa radon lung cancer study
had four major components: 1) rapid reporting of cases;
2) a mailed questionnaire followed by a face-to-face
interview; 3) a comprehensive radon exposure assessment;
and, 4) independent histopathologic review of lung cancer
tissues The rapid case reporting allowed personal interviews
with a high percentage (69 %) of cases, providing much
more accurate information than can be obtained by interviewing
relatives. This study represents the most detailed attempt,
to date, to reconstruct total individual radon exposure.
Exposure reconstruction included on-site measurements
of home radon with year-long tests on every level of
the home, in current & historical bedrooms, and
in 'in-home' work areas. These in-home measurements
were linked with individual movements within the home.
Outside exposure as well as exposures in other buildings
were included in the reconstruction. The independent
tissue review (performed on 96% of lung cancer tissues)
provided a reliable classification of lung cancer cases.
"The risk estimates obtained
in this study suggest that cumulative [total] radon
exposure in the residential environment is significantly
associated with lung cancer risk." After adjusting
for age, smoking, and education, and using categorical
radon exposure levels, a 15 year exposure at levels
equivalent to EPA's action level of 4 pCi/L yielded
excess odds of 0.50 i.e., an increase in lung cancer
risk of 50% (95% confidence interval: 0.004, 1.81) for
total cases and excess odds of 0.83 for cases with personal
interviews i.e., an increase in lung cancer risk of
83% (95% confidence interval: 0.11, 3.34). The higher
risk found for cases with personal interviews vs. the
total cases most probably reflects the more accurate
exposure assessment obtained from interviews with cases
vs. interviews with relatives.
EPA's View of the Study:
The Iowa study is exceptionally
well designed and well executed. It adds to the body
of knowledge which designates residential radon as the
second leading cause of lung cancer. It supports EPA's
position and the National Academy of Sciences' Institute
of Medicine's 1999 report that radon exposure in homes
is a public health problem. It confirms EPA's, the Center
for Disease Control's, and the Surgeon General's positions
that all homes should be tested for radon, and all homes
testing over 4 pCi/L should be fixed. In terms of scientific
advancements, the study breaks new ground in estimating
total individual radon exposure.
University of Iowa Center for
Health Effects of Environmental Contamination Press
Release. Contains the Press Release; Abbreviated Findings;
Study Methodology; Questions and Answers About the Study;
and, Study Contact and Additional Radon Information.
To: R. William Field, Ph.D.College
of Public Health, Department of EpidemiologyUniversity
of Iowa, Iowa City, Iowa
to commend you on your Iowa Radon Lung Cancer Study.
I believe the methods you used to reduce the inherent
random error associated with ascertaining long-term
residential radon exposure are critical to validly assessing
the lung cancer risk from this source. As you correctly
point out the random error in estimating radon exposure
has the potential to substantially underestimate the
slope of the dose-response curve. Your estimates of
risk are similar to my own in our study of lung cancer
among Missouri women, where we used historic estimates
of radon exposure from cumulative measures of radon
progeny in glass. I believe that most studies published
to date have been ineffective in reducing measurement
error and their dose-response results have suffered
from a bias toward the null. I look forward to the discussion
your results will generate and urge you to complete
the analysis of you radon progeny in glass measurements
data. Along with your current manuscript, that data
should help clarify the true nature of the dose-response
curve between residential radon and lung cancer risk.
Again congratulations on a job well done.
Michael Alavanja, Dr. P.H.
Senior Investigator, Division of Cancer Epidemiology
National Cancer Institute
Study is a significant addition to our already strong
understanding of indoor radon and lung cancer. Its particular
importance lies in the careful methodologic work done
by the investigators on some nagging scientific issues--particularly
the estimation of lifetime exposure to radon.
Dr. Jonathan Samet,
Professor and Chairman, Department of Epidemiology,
School of Hygiene and Public Health,
Johns Hopkins University, Baltimore, Maryland.