Where It’s Found

Though perchlorate can be man-made, it is well-documented that perchlorate is also naturally occurring; it is formed atmospherically. For example, it is naturally present in some fertilizers used in organic farming. Naturally occurring perchlorate has been found in water supplies, soils, arid-region plants and even on Mars.

Until recently, perchlorate was detected in only a few places where it was either manufactured or used in large quantities. In 1997 and thereafter, new techniques were developed that made it possible to detect perchlorate in water at very low levels — in the parts per trillion (ppt). Because of these advancements, low levels of perchlorate have been detected in more places. Once perchlorate was detected at these low levels, industry and government began working together to review and study the health effects of perchlorate, resulting in several new studies that showed these low levels have no measurable effect on human health. Treatment technologies have also been developed and put in place to address perchlorate contamination. The US Environmental Protection Agency determined in June 2020 that perchlorate did not meet the requirements for additional national regulation under the federal Safe Drinking Water Act.