[BenLurkin]

Large doses of the chemical, in widespread use by the Defense Department since the 1950's, have been shown to inhibit the thyroid gland's ability to take up iodide . . .

How large is 'large'? Would I have to take a bite out of a solid rocket motor to get close?

[DaveTesla]

Perchlorate does not damage the thyroid gland. High levels of perchlorate, above 200 parts per billion (ppb), can temporarily affect the thyroid's ability to absorb iodide from the bloodstream, but this in itself is not an adverse effect (it happens naturally in every human as a result of diet and other factors). Perchlorate is not stored in any human tissues, including the thyroid gland.