According to the Environmental Protection Agency: "Perchlorate is both a naturally occurring and man-made chemical, and scientific research indicates that it may impact the normal function of the thyroid, which produces important developmental hormones. Thyroid hormones are critical to the normal development and growth of fetuses, infants and children."

Regulations and Testing

Perchlorate is not regulated at the federal or state level in Colorado. However, Denver Water tested its drinking water for perchlorate as early as 1997. Additional testing has been done since 2002, with most of the results falling below the level labs can even accurately report. The highest drinking water result occurred in 2004 – a value of 0.68 µg/L (parts per billion). For comparison, California has a regulation of 6.0 µg/L, nearly 10 times higher than those results.

Given the results of previous sampling for perchlorates, along with increased regulatory testing requirements for other compounds, Denver Water has shifted resources to other water quality testing needs and is no longer sampling for this compound.

What this means for Denver Water

If perchlorate regulations are imposed, they are not likely to have a water quality impact on Denver Water because Denver Water has a surface water system that comes from snowmelt or precipitation, and systems fed from groundwater or wells are the ones that typically experience problems with perchlorate.