Perchlorate can interfere with iodine uptake by the thyroid gland. It is used as a drug to combat hyperthyroidism. It also occurs naturally and is continually

Perchlorate can interfere with iodine uptake by the thyroid gland. It is used as a drug to combat hyperthyroidism. It also occurs naturally and is continually produced in the atmosphere. There is no maximum contaminate level goal (MCLG) set and thus no maximum level set for groundwater. They did setup some interim guidance back in 2008, and advised 15ppb. Overall, doesn't look super dangerous.