Perchlorate can interfere with iodide uptake into the thyroid gland. The thyroid is a central control point for a variety of hormonal responses including iodine levels. In adults, the thyroid helps to regulate metabolism. In pregnant women, severe iodide deficiency can result in major neurodevelopmental deficits and goiter in their offspring. Lesser degrees of iodide deficiency may also cause important neurodevelopmental deficits in infants and children.

Perchlorate is highly soluble in water and has been detected in ground and surface water in 26 states and one territory. While it has often been detected in water supplies in close proximity to sites where solid rocket fuel is manufactured or used, there are also many locations in the United States lacking a clearly defined source.

Following extensive review and analysis of the best available science, the U.S. Environmental Protection Agency (EPA) published a final action on July 21, 2020. In it, EPA determined that perchlorate does not occur “with a frequency and at levels of public health concern” within the meaning of the SDWA. In addition, in the judgment of the EPA administrator, regulation of perchlorate does not present a “meaningful opportunity for health risk reduction for persons served by public water systems.” Accordingly, EPA is withdrawing its 2011 determination and is making a final determination not to regulate perchlorate, and therefore will not issue a NPDWR for perchlorate at this time.

Two states have promulgated regulations for perchlorate, California (6 ug/L) and Massachusetts (2 ug/L). Several other states have issued advisory levels for perchlorate as summarized by EPA. The Agency has also documented the progress made in decreasing perchlorate levels.

If you are concerned about perchlorate in your drinking water, you may consider purchasing a home treatment device. However, in order to make a well-informed and cost-effective decision, consider:

• Checking with your water system or consumer confidence report to learn about the amount of total perchlorate in your water.
• Identifying a device that has been independently certified to remove perchlorate.

NSF International, the Water Quality Association, Underwriters Laboratories and CSA International all certify home treatment products for removal of contaminants. The relevant perchlorate removal standard is NSF/ANSI Standard 58. If you choose to use a home treatment device, it is very important to follow the manufacturer's operation and maintenance instructions carefully in order to make sure the device works properly.