The FDA adopted the convention of a hundredfold margin of safety years ago when it began setting standards for acceptable quantities of food additives. The assumptions behind the hundredfold margin are that humans are ten times more sensitive to adverse effects of chemicals than are test animals, and that the weak in the human population are ten times more sensitive than the healthy. Compounding the tens, the FDA arrived at the hundredfold margin. Some in the anti-chemical movement have even demanded the government a thousandfold margin, although no more scientific justification for that exists than for the hundredfold margin. We can only offer probabilities that there will, in fact, be no harm.
Absolute safety is the complete absence of harm .
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