The Delaware County Water Company supplies surface water to about 150,000 people through 56,000 connections without any health-based violations on record. From 2014 to 2015, federal monitoring showed chromium-6, also called hexavalent chromium or chromium(VI), was detected in 15 out of 16 samples with a highest measurement of 0.75 micrograms per liter (0.75 ppb). Total chromium was also measured with a highest value of 0.84 micrograms per liter. These findings are from system-wide sampling and do not reflect any single household's water.
How does the oxidation state of chromium change between the source water, distribution mains, and your tap?
Chromium appears mainly in two oxidation states in water: trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)). Hexavalent chromium is more mobile and typically originates in oxidizing environments, while trivalent chromium is less soluble and often forms in reducing conditions. Between the surface water source and the tap, chemical and physical changes can shift chromium's oxidation state. Factors like pipe materials, water pH, and residual disinfectants influence this process. Consequently, measured chromium-6 at the distribution system level may differ from the actual form and concentration at an individual tap. To know your home's specific water quality, testing directly on-site is necessary.
What are the typical sources of geogenic hexavalent chromium compared to industrial plating contamination?
Hexavalent chromium can arise from natural geochemical processes, especially in arid and alkaline aquifers where chromium-bearing minerals can oxidize and release Cr(VI) into groundwater. However, Delaware County's water source is surface water, meaning natural geological sources are less likely contributors here. Industrial activities such as chromium plating release chromium-6 into the environment, but current data for Delaware County’s public system does not attribute chromium-6 levels to any violation or health-based exceedance. The chromium-6 detected likely reflects typical background presence in surface water rather than point-source industrial pollution.
How should Delaware County’s chromium-6 record be compared with neighboring counties without overreading the data?
When reviewing chromium(VI) results across counties, it is important to understand that federal sampling captures general system trends and not individual household conditions. Delaware County’s highest chromium-6 measurement of 0.75 micrograms per liter is below any federal maximum contaminant level (MCL), as no MCL currently exists for hexavalent chromium alone. Comparisons with neighboring areas should consider differences in water source type, sampling frequency, and treatment practices. Small variations in detection and median values do not imply better or worse water quality on a household level but rather reflect system-wide sampling outcomes.
Why do aesthetic secondary standards differ from health-based limits for chromium-6?
Secondary standards for parameters like chromium or total dissolved solids relate to water taste, appearance, and staining potential rather than health risks. For chromium(VI), the EPA has established a total chromium MCL of 100 micrograms per liter that applies collectively to trivalent and hexavalent chromium forms. The detected chromium-6 levels in Delaware County’s system are far below this threshold. Since no health-based limit exists specifically for hexavalent chromium, the recorded detections indicate presence but not unsafe levels. Understanding this distinction helps prevent misinterpretation of what chromium-6 concentrations mean for water safety and usability.
How does treated water at your tap differ once a Pentek Chromium-6 Filter is in use?
The Pentek Chromium-6 Filter uses specific media designed to reduce hexavalent chromium from water at the point of use. After water passes through this filter, the concentration of chromium(VI) at the tap is lowered substantially, often to levels indistinguishable from background trace amounts. This treatment changes the water quality by effectively converting or capturing chromium-6, addressing concerns about its presence. Because the filter ships ready to configure, it can be added directly at the household level without reliance on system-wide changes.
To determine the chromium-6 level in your own water, the recommended step is to arrange a laboratory test specifically measuring hexavalent chromium. A test result showing chromium-6 below the reporting level would confirm that no further action is needed, while elevated levels can guide the choice of point-of-use filtration such as the Pentek Chromium-6 Filter.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-02-11. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Delaware County Water Company, Inc. (OH2101412), OH: 32 results across 2 listed contaminants, 28 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L
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