1. Reading a Chromium-6 Laboratory Test Report
A lab report for household water tested for chromium-6, also known as hexavalent chromium or Cr(VI), typically lists concentrations in micrograms per liter (µg/L), which is numerically equivalent to parts per billion (ppb). This figure indicates the measured amount of chromium(VI) detected above the reporting threshold, but it is important to recognize that detection alone does not imply a health violation or unsafe level. For example, local government monitoring in the Glen Burnie-Broadneck system serving Anne Arundel County found chromium-6 concentrations ranging up to 0.14 µg/L, with a median detected level of 0.046 µg/L.
2. Differences Between Ion Exchange and Reverse Osmosis for Chromium(VI)
When addressing chromium(VI) in household water, ion exchange and reverse osmosis (RO) technologies differ in their approach. Ion exchange uses resin beads that specifically attract and exchange chromium(VI) ions for less harmful ions, effectively targeting hexavalent chromium. In contrast, reverse osmosis forces water through a semipermeable membrane that screens out a broad range of dissolved solids, including chromium(VI), although both methods require proper setup to function effectively. Understanding these distinctions can guide decisions when selecting a suitable filtration solution.
3. Changes in Chromium Oxidation State from Source to Tap
Chromium in water can exist in multiple oxidation states, primarily chromium(III) and chromium(VI). While sourced from groundwater, chromium(VI) can undergo chemical changes during its movement through well systems and distribution mains. Oxidation or reduction reactions influenced by water chemistry and treatment steps may convert chromium between its trivalent and hexavalent forms before reaching your tap. These transformations can affect the form and concentration of chromium detected at the point of use compared to the source.
4. Impact of Sampling Depth and Source Type on Expected Chromium(VI) Levels
The depth at which a water sample is collected, as well as the well's depth and source type, influence measured chromium(VI) levels. Deeper wells often access water with different chemical characteristics than shallow wells, potentially altering chromium speciation and concentration. Similarly, testing at the water main or distribution points may yield different results from household tap samples due to water aging and distribution system factors. Recognizing these variables is essential when interpreting data from government surveys or your own tests.
5. Purpose and Limitations of the UCMR3 Survey for Chromium(VI)
The Unregulated Contaminant Monitoring Rule 3 (UCMR3) conducted by the EPA collected chromium-6 data nationally from 2013 to 2015 to better understand its occurrence in public water systems. For the Glen Burnie-Broadneck system, this entailed 24 samples, 17 of which showed chromium-6 detected above a reporting level of 0.03 µg/L, with a maximum of 0.14 µg/L recorded. However, these results represent system-wide data, not individual household water quality. The survey was not designed to provide compliance information or health enforcement but to inform future regulation considerations and water providers. Therefore, UCMR3 results serve as a regional reference rather than a direct assessment of any single home’s water.
6. Why Total Chromium Results Cannot Confirm Chromium(VI) Levels
Total chromium measurements encompass all chromium oxidation states combined, including chromium(III) and chromium(VI). Because these forms differ chemically and in health considerations, a total chromium concentration does not specify the amount of chromium-6 present. For example, the local system showed one detection of total chromium at 0.21 µg/L but this does not clarify how much of that is hexavalent chromium. Distinguishing between these types requires specific chromium-6 tests.
7. Final Step: Testing to Know Your Household Water
To conclusively determine your household’s chromium(VI) concentration, the critical step is ordering a laboratory test that specifically measures hexavalent chromium at your tap. This test reports chromium-6 in micrograms per liter or parts per billion, enabling you to compare your water to regional occurrences documented by government surveys. With this verified information, you can select the appropriate approach to configure your equipment for addressing chromium-6, such as the Fleck Chromium-6 Filter, which is designed to effectively reduce hexavalent chromium in residential water supplies.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-08-06. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Glen Burnie-Broadneck (MD0020017), MD: 48 results across 2 listed contaminants, 18 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L