What do government samples say about chromium-6 in Memphis public water?
Federal data from 2013 to 2015 on the Memphis Light, Gas & Water system, serving over 659,000 people in Shelby County, found chromium-6 detected in 7 out of 40 samples. The highest measured concentration was 0.1 micrograms per liter (µg/L or parts per billion), with a median detected level of 0.06 µg/L. Importantly, no federal health-based violations for chromium-6 or total chromium have been recorded for this water system, which sources its supply from groundwater.
How does chromium’s oxidation state change from well to tap?
Chromium occurs primarily in two states: trivalent chromium(III) and hexavalent chromium(VI), known as chromium-6. Hexavalent chromium is more mobile in water and can transform chemically during treatment and distribution. The water leaving the well can contain chromium-6, but factors such as the groundwater environment, water chemistry, and exposure to oxygen in the distribution mains can alter its oxidation state before reaching the tap. Thus, concentrations measured in the distribution system do not always directly reflect the well water’s chromium speciation.
What was the purpose and limits of the UCMR3 chromium-6 monitoring for a household’s water?
The Unregulated Contaminant Monitoring Rule 3 (UCMR3) survey conducted by the EPA measured chromium-6 to gather nationwide occurrence data, not to assess compliance or safety at individual homes. Sampling covered large public water systems like Memphis Light, Gas & Water, providing system-wide averages and detection rates. Because sampling points and times vary, and household plumbing conditions differ, residents cannot determine their own tap’s chromium-6 level solely from these results. Personal water testing is necessary for specific home measurements.
What are common sources of hexavalent chromium and how does geology affect its presence?
Hexavalent chromium in groundwater originates from two main sources: geogenic and industrial. Geogenic chromium-6 forms naturally in arid or alkaline aquifers through mineral dissolution, while industrial sources such as metal plating and manufacturing releases can elevate localized levels. In Shelby County, the water system’s groundwater origins and absence of recorded violations suggest levels reflect natural background conditions rather than industrial contamination.
How does the C-Series System address chromium-6 in household water?
The C-Series Chromium-6 Filter uses specialized filtration media designed to reduce the concentration of hexavalent chromium by converting chromium(VI) to less mobile forms or physically capturing chromium particles. The unit ships ready to configure for use in home water treatment setups and can provide targeted reduction based on measured demand. It is a documented solution tailored to address concerns about chromium-6 in residential water supplies.
Why do secondary standards for chromium-6 differ from health-based limits?
Standards for chromium-6 in water can be classified into health-based and aesthetic secondary standards. While there is no federal maximum contaminant level (MCL) specifically for hexavalent chromium, total chromium has an MCL of 100 µg/L. Secondary standards address taste, staining, and corrosion potential rather than health risks. Exceeding these aesthetic thresholds does not constitute a health violation but may prompt treatment for consumer preferences. Shelby County’s public water record shows chromium-6 levels well below health risk thresholds.
For Shelby County residents concerned about chromium-6 detected by EPA monitoring and seeking a reliable approach to water safety at home, the C-Series Chromium-6 Filter offers a scientifically supported option. To decide on treatment capacity and configuration, testing your own water is essential to understand your household’s chromium-6 concentration and demand.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-12-08. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Memphis Light, Gas & Water (TN0000450), TN: 80 results across 2 listed contaminants, 7 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L