It remains unclear to me how Cohen’s ecological data can be used to test LNT (or any other predictive theory). Cohen states that “…case-control studies investigate the causal relationship between radon exposure and lung cancer, whereas our work has the much more limited objective of testing the linear no-threshold theory” (Health Physics, Volume 72(4), page 625, April 1997). It is absurd to suggest that testing the LNT theory is not a test of a causal relationship. The LNT theory, in this context, only has meaning if radiation causes cancer. If Cohen’s work does not test for a causal relationship, how can his data be a test for LNT (or any other predictive theory)?
Cohen goes on to say “We have…never claimed that low level exposure to radon is protective against lung cancer” (Health Physics, Volume 72(4), page 625, April 1997). If the data refute LNT then what do the data support if not hormesis (as suggested by the strong negative correlation for radon concentrations <150 Bqm-3)? Cohen cannot have it both ways.
Cohen quotes Richard Feynman in support of his test of LNT. According to Feynman “we look for a new law by the following process: first we guess at it. Then we compute the consequences of the guess to see what would be implied if this law we guessed is right. Then we compare the result of the computation with …observation, to see if it works. If it disagrees with experiment [the law] is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is-if it disagrees with experiment it is wrong. That is all there is to it.” (Health Physics, Volume 72(4), page 624, April 1997). Implied in Feynman’s statement is that the data provide a bona fide test of the theory. If the data are erroneous (e.g., use of faulty data analysis, use of inappropriate statistical tests, use of inappropriate experimental methods) then the data do not provide a test of the theory even though the data, on its face, might suggest the theory is wrong.
Kenneth L. Mossman
Professor of Health Physics
Director, Office of Radiation Safety
Arizona State University