Along the lines of Songwrongers italicized paragraph above: I saw a TV documentary last spring about scientists beginning to question a basic premise of toxicology, that there is a safe limit for chemical consumption and below that one need not worry. It was related to studies of weight gain in spite of healthy eating and exercise. In this case certain chemicals were found to mock estrogen in the human body when present in very tiny, barely measurable amounts, even though neither weight gain nor traditional toxicity showed with much higher concentrations.

Unfortunately scientists don't publish what the can't measure. It's only with the modern electronic measuring devices that such tiny quantities could be measured that the low-level toxicity could come to light. Not much room in science for common sense, which would say that just because it's good at x level doesn't mean it's good at levels below or above that.