Regulation of Perchlorate at Low Levels in Drinking Water:
A High Stakes Decision
Low levels of perchlorate have no measurable health effects
A sequence of three events is required for perchlorate to have any adverse effect on health, each requiring higher doses of perchlorate. There is no measurable effect at all below 245 ppb, and it takes at least 100 times that amount, consumed daily over a long period of time (years according to some research), to have any kind of adverse health effect.
A PERSON WOULD HAVE TO DRINK AT LEAST 500 GALLONS OF WATER WITH 20 PPB OF PERCHLORATE EVERY DAY BEFORE THERE COULD BE ANY ADVERSE EFFECT.
First: Perchlorate exposure must be sufficiently high (levels of about 245 ppb) to prevent the thyroid from getting its usual amount of iodide. Research has shown it takes levels far greater than what's currently being found in water supplies to accomplish this first event, which even in itself is not harmful, as the body can naturally compensate for this in a couple of ways, including drawing upon the huge store of iodide within the thyroid gland itself. (On average, most Americans get at least twice the 150-200 mg recommended daily amount of iodide in their diet.)
Next: Exposure must be great enough to overwhelm the body's normal adaptive process, which routinely adjusts and normalizes thyroid hormones as needed. Scientific research indicates this does not occur at levels below 14,000 ppb.
Finally: Exposure must be high enough (more than 14,000 ppb) to reduce thyroid hormone levels for a long period of time. An adverse health effect would require daily consumption of more than 14,000 ppb in drinking water. This would require drinking at least 500 gallons of water per day, with each gallon containing 20 ppb perchlorate.
Each of these events is fully reversible if perchlorate exposure declines or stops. Perchlorate is not stored in any part of the body.