Basic HTML Version
Papers
Radon in homes and risk of lung cancer: collaborative analysis of
individual data from 13 European case-control studies
S Darby, D Hill, A Auvinen, J M Barros-Dios, H Baysson, F Bochicchio, H Deo, R Falk, F Forastiere, M Hakama, I Heid,
L Kreienbrock, M Kreuzer, F Lagarde, I Mäkeläinen, C Muirhead, W Oberaigner, G Pershagen, A Ruano-Ravina,
E Ruosteenoja, A Schaffrath Rosario, M Tirmarche, L Tomá
B
ek, E Whitley, H E Wichmann, R Doll
Abstract
Objective
To determine the risk of lung cancer associated with
exposure at home to the radioactive disintegration products of
naturally occurring radon gas
Design
Collaborative analysis of individual data from 13
case-control studies of residential radon and lung cancer.
Setting
Nine European countries.
Subjects
7148 cases of lung cancer and 14 208 controls.
Main outcome measures
Relative risks of lung cancer and
radon gas concentrations in homes inhabited during the
previous 5-34 years measured in becquerels (radon
disintegrations per second) per cubic metre (Bq/m
3
) of
household air.
Results
The mean measured radon concentration in homes of
people in the control group was 97 Bq/m
3
, with 11% measuring
> 200 and 4% measuring > 400 Bq/m
3
. For cases of lung
cancer the mean concentration was 104 Bq/m
3
. The risk of lung
cancer increased by 8.4% (95% confidence interval 3.0% to
15.8%) per 100 Bq/m
3
increase in measured radon (P = 0.0007).
This corresponds to an increase of 16% (5% to 31%) per 100
Bq/m
3
increase in usual radon—that is, after correction for the
dilution caused by random uncertainties in measuring radon
concentrations. The dose-response relation seemed to be linear
with no threshold and remained significant (P = 0.04) in
analyses limited to individuals from homes with measured
radon < 200 Bq/m
3
. The proportionate excess risk did not
differ significantly with study, age, sex, or smoking. In the
absence of other causes of death, the absolute risks of lung
cancer by age 75 years at usual radon concentrations of 0, 100,
and 400 Bq/m
3
would be about 0.4%, 0.5%, and 0.7%,
respectively, for lifelong non-smokers, and about 25 times
greater (10%, 12%, and 16%) for cigarette smokers.
Conclusions
Collectively, though not separately, these studies
show appreciable hazards from residential radon, particularly
for smokers and recent ex-smokers, and indicate that it is
responsible for about 2% of all deaths from cancer in Europe.
Introduction
In many countries exposure in the home to short lived radioac-
tive disintegration products of the chemically inert gas
radon-222 is responsible for about half of all non-medical expo-
sure to ionising radiation.
1
Radon-222 arises naturally from the
decay of uranium-238, which is present throughout the earth’s
crust. It has a half life of four days, allowing it to diffuse through
soil and into the air before decaying by emission of an particle
into a series of short lived radioactive progeny. Two of these,
polonium-218 and polonium-214, also decay by emitting par-
ticles. If inhaled, radon itself is mostly exhaled immediately. Its
short lived progeny, however, which are solid, tend to be depos-
ited on the bronchial epithelium, thus exposing cells to irradia-
tion.
Air pollution by radon is ubiquitous. Concentrations are low
outdoors but can build up indoors, especially in homes, where
most exposure of the general population occurs. The highest
concentrations to which workers have been routinely exposed
occur underground, particularly in uranium mines. Studies of
exposed miners have consistently found associations between
radon and lung cancer.
2 3
Extrapolation from these studies
suggests that in many countries residential radon, which
involves lower exposure in much larger numbers of people,
could cause a substantial minority of all lung cancers. This is of
practical relevance because radon concentrations in existing
buildings can usually be reduced at moderate cost—for example,
by increasing underfloor ventilation—while low concentrations
can usually be ensured at reasonable or low cost in new
buildings—for example, by installing a radon proof barrier at
ground level. These extrapolations, however, depend on
uncertain assumptions because the levels of exposure in miners
that produced evident risk were usually much higher, lasted
only a few years, and took place under different particulate air
and other conditions.
1–3
Moreover, history on smoking is often
lacking, or limited, in the studies of miners and some
miners were also exposed to other lung carcinogens such as
arsenic.
Studies to estimate directly the risk of lung cancer associated
with residential radon exposure over several decades have been
conducted in many European countries. Individually these
studies have not been large enough to assess moderate risks
reliably. Greater statistical power can be achieved by combining
information from several studies, but this cannot be done satis-
factorily from published information. Urban areas tend to have
lower radon concentrations than rural ones as the underlying
rock is usually sedimentary and more people live upstairs in
apartments. Urban areas also usually have a higher prevalence
of smoking. Hence, radon concentrations in homes tend to be
negatively correlated with smoking,
4–6
and a large dataset is
needed to correct for this reliably. We therefore brought
together and reanalysed individual data from all European
studies of residential radon and lung cancer that satisfied
certain criteria.
Cite this article as: BMJ, doi:10.1136/bmj.38308.477650.63 (published 21 December 2004)
BMJ
Online First bmj.com
page 1 of 6