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Additionally, by the early 1980s, the epidemiological studies of underground miners,
along with compelling experimental evidence, had provided convincing evidence that
radon progeny could cause lung cancer (NRC, 1988). As national programs for testing
and mitigation were implemented, critics questioned whether the scientific evidence on
risks of residential radon was sufficiently certain to justify programs of this scale.
In response to the need for information on risks from indoor exposure, epidemiological
studies directed at lung cancer in the general population were initiated in the 1970s and
1980s. The first wave of studies was largely ecological in design and provided mixed
findings because of inherent flaws of this approach (Stidley & Samet, 1993). Case-
control studies of lung cancer, a more
appropriate design, were also implemented in
the United States, Europe, and elsewhere.
Some of the first studies did not incorporate
measurements of indoor radon, as do those
reported in this issue of the Journal of
Toxicology and Environmental Health.
Rather, they used surrogate measures, such
as type of housing construction, and the
resulting data could not provide the
quantitative estimates of risk needed for
policy purposes.
By the mid to late 1980s, many studies of
more sophisticated design with larger sample
sizes were undertaken. The data for individuals in these studies, since completed, have
now been pooled. The findings in this issue, although having the inherent limitation of
exposure measurement error, generally support the carcinogenicity of radon exposure
in homes and are consistent with expectations of risk based on downward extrapolation
of models based on the miner data.
The new findings support the national programs for radon measurement and mitigation
that have long been in place. When the case-control studies were implemented, it
was with the expectation that forthcoming evidence would reduce uncertainties about
the carcinogenicity of indoor radon and offer an alternative basis for risk estimation,
beyond applying the risks observed in the underground miners to the general
population. As the case-control studies were implemented and planned, the challenge
of obtaining the certainty sought by policymakers was quickly apparent. While the
individual studies were designed primarily to test the hypothesis that radon was a cause
of lung cancer, the more relevant question for setting policy direction was whether
reliance on risk assessments using the miner data would exaggerate or underestimate
the actual risks to the population. Addressing this question is more demanding of study
design than the less relevant test of the null hypothesis that indoor radon does not
cause lung cancer.