Substantial research has been conducted since the mid-1990s to improve scientific and medical understanding of perchlorate’s health effects. These studies show perchlorate has no measurable effects on human beings at levels many times higher than the minute amounts being found in some drinking water supplies.
Perchlorate has no measurable health effect at levels below 245 parts per billion (ppb). According to credible medical experts and science it takes more than 50 times this amount to have any adverse health effect.
Credible studies show perchlorate’s direct effects on human health are limited to the thyroid. High levels of perchlorate can prevent the thyroid gland from absorbing iodide (which it needs to make hormones) from the bloodstream. This in itself is not dangerous however, because the body automatically compensates for this.
An adult would have to drink at least 400 gallons of water with 20 ppb of perchlorate per day before there could be any risk of adverse effect.