You can have ‘toomuch of a good thing’. But can you have ‘too little of a bad thing’? Professor
Calabrese has shown that a great many things that are damaging in large quantities may –
in small doses, below a certain threshold – do no harm or even be beneficial. It seems that
very small doses of potentially damaging substances can stimulate the repair and protection
mechanisms that our bodies have evolved to help us survive.
But for radiation, it has been conventionally assumed by most regulatory authorities that
there is no minimum threshold, let alone any ‘hormesis’ – that is, any beneficial effect – from
exposure to levels of radiation a little higher than the natural background level.