Is Hexavalent Chromium Naturally Occurring in Harris County's Water or from Industrial Plating?
Hexavalent chromium, also called chromium-6 or chromium(VI), can originate from different sources. In Harris County, the City of Houston’s public water system draws from surface water rather than groundwater aquifers. This means geogenic chromium-6—commonly found in arid and alkaline aquifers—is less likely the main contributor here. Instead, chromium-6 may be present due to environmental factors affecting surface sources, including legacy industrial activities within the region. Government data from 2013 to 2015 reports multiple detections of chromium-6 in the municipal water supply, reflecting measurable but varying concentrations.
What Household Water Issues Might Indicate the Presence of Chromium(VI), and What Symptoms Are Unrelated?
Residents who notice unusual taste, staining, or corrosion sometimes suspect chromium-6; however, these symptoms alone do not confirm its presence or level. Chromium-6 itself is colorless and odorless, so it does not cause visible changes or distinct smells in water. Common household water quality issues—such as hardness, iron staining, or sulfur odors—are unrelated to chromium(VI). To understand potential chromium-6 concerns, testing is essential rather than relying on sensory clues.
What Does a Certified Laboratory Test Report for Chromium-6 Show, and How Should You Interpret It?
Certified labs measure chromium-6 in micrograms per liter (µg/L), equivalent to parts per billion (ppb). A positive detection indicates the instrument measured chromium(VI) above a reporting threshold; this is not a compliance test but a factual concentration result. For example, the City of Houston recorded chromium-6 detections ranging from just above 0.03 µg/L up to 6.661 µg/L during federal unregulated contaminant monitoring. However, these measurements are about the system overall and do not specify what a single household’s water contains. Only a direct test of your own tap water can establish that information.
How Do Aesthetic Secondary Standards for Chromium-6 Differ from Health-Based Limits?
Unlike health-based standards, secondary standards focus on qualities affecting taste, appearance, or plumbing durability. For chromium-6, no federal maximum contaminant level (MCL) currently exists, but total chromium is regulated with an MCL of 100 µg/L. The aesthetic thresholds for chromium can govern taste or staining tendencies but are not health limits. This distinction is important when interpreting public water system data: detecting chromium-6 above a reporting level does not mean the water is unsafe or legally noncompliant.
What Does the Range of Chromium(VI) Concentrations Measured by the City of Houston Mean Compared to Federal Standards?
The federal data for the City of Houston’s system, serving nearly 3 million in Harris County, shows chromium-6 was detected in 178 out of 199 samples at levels between 0.03 µg/L and 6.661 µg/L. Although detected, none of these results surpass the total chromium MCL of 100 µg/L, and there is no MCL established for chromium-6 specifically. This means that while chromium(VI) is measurable, these values are within the range expected from source water quality monitoring and do not represent violations or unsafe water per federal guidelines.
What Should You NOT Conclude from Area Chromium-6 Data About Your Home Water?
Data from the City of Houston’s public water system is about the system-wide water quality and cannot predict your household’s exact chromium-6 levels. Detection alone is not a health violation or proof of unsafe water. You should not assume your well or tap water contains chromium(VI) at any specific concentration without a certified test. For homeowners concerned about chromium-6, obtaining a targeted laboratory analysis is the only way to know the chromium(VI) concentration in their water. To help manage chromium-6, equipment that ships ready to configure, such as the C-Series Chromium-6 Filter, uses advanced filtration technology designed specifically for this constituent and can provide an additional layer of water quality assurance.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-04-28. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for City of Houston (TX1010013), TX: 398 results across 2 listed contaminants, 241 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L