Iowa Radon Lung Cancer Study (IRLCS)
Study Title:
"Residential Radon Gas Exposure and Lung Cancer", American
Journal of Epidemiology, June 2000
Authors:
R. William Field, Daniel J. Steck, Brian J. Smith, et al
Study Population:
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).
Background:
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 tissuesThe 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.
Results:
"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.