Low-dose risk, hormesis, analogical and logical thinking.

The hormesis theory proposes the low-dose beneficial and high-dose detrimental pattern, existing for specific conditions, as a "general default assumption" for toxicology and carcinogenicity. Crump and Kitchin and Drane underline that in a post hoc retrospective scientific literature searching for hormetic dose-response patterns, the consideration of the whole available relevant studies is necessary and, for statistical testing purposes, for instance at a 0.05 standard level, a P value obtained from 1 - (1 - P)(n) = 0.05 (i.e., P = 0.0005 for 100 examined cases) should be used (otherwise, by definition, 5 "positive" results are expected by chance over 100 cases). The hypothesis, based on some experimental data on rodents, by Calabrese and Baldwin, of an hormetic effect of 2,3,7,8-TCDD at the 1-10 ng/kgbw/day dose, of Na-saccharine in the < or = 1% of diet exposure range, of Cadmium Chloride in the 0-5 micromol/kg dose range, single injection, and of neutrons in the 0- to 2-rad dose range, are not confirmed, and, rather, are contradicted, when the whole relevant data presented by international and national agencies are considered. As far as the radiation risk is in particular concerned, a recently published epidemiological study on more than 400,000 nuclear plant workers, co-ordinated by the IARC has indicated a small, but significant risk, at the current exposure limits, and possibly below them. Therefore, the hormesis theory-based criticism of current radiation protection criteria, assumed to be excessively conservative, is not justified. Also not justified is the assumption that "by dismissing hormesis, regulatory agencies such as U.S. EPA deny the public the opportunity for optimal health and avoidance of diseases;" rather, the contrary is here considered true. Analogical considerations are not necessarily logical ones and the single result should be considered in its whole context.