You may notice a subtle metallic or chemical taste in your household water or observe slight discoloration after your water equipment has failed. In the Virgin Islands, public water system monitoring has shown the presence of chromium-6, also known as hexavalent chromium or chromium(VI), at low levels. This ion is a naturally occurring form of chromium that may be found dissolved in water sources and can affect taste and appearance.
How Ion Exchange and Reverse Osmosis Treat Chromium(VI) Differently
Chromium-6 can be addressed using various water treatment technologies, notably ion exchange and reverse osmosis. Ion exchange uses resin beads to attract chromium(VI) ions specifically, exchanging them for less problematic ions, thereby reducing chromium levels effectively. Reverse osmosis, on the other hand, forces water through a semipermeable membrane that blocks many contaminants including chromium(VI). Each method acts differently on the chemistry of chromium(VI), with ion exchange suited for targeted chromium control and reverse osmosis offering broader contaminant reduction.
How Chromium’s Oxidation State Changes from Source to Tap
Chromium in water primarily exists in two oxidation states: trivalent chromium (chromium III) and hexavalent chromium (chromium VI). The oxidation state can shift due to chemical conditions as water moves from the source well to the public distribution system and finally to your tap. Treatment and environmental factors influence these changes. For instance, chromium can oxidize to chromium(VI) during water treatment or distribution, which affects its solubility and mobility.
Implications for Different Households: Large, Second Homes, and Seasonal Properties
The amount of water used and the frequency of water flow can influence how chromium-6 interacts with household plumbing. Large households with higher water demand may experience slightly different water chemistry compared to seasonal or second homes with intermittent use. Stagnant water during periods of non-use in seasonal homes can affect chromium forms and concentrations temporarily. Understanding these factors helps tailor water treatment choices effectively.
Why California Established a 10 µg/L Limit and Its Relevance Elsewhere
California set a public health goal of 10 micrograms per liter (µg/L) for hexavalent chromium based on comprehensive studies related to long-term exposure. The federal government has not established a maximum contaminant level (MCL) specifically for chromium-6, though it sets a total chromium MCL of 100 µg/L. The regional detection of chromium-6 in Virgin Islands water is well below both California’s health goal and the federal total chromium MCL, but the California standard illustrates ongoing attention to chromium-6’s potential effects.
Interpreting the Government Sampling Results in the Virgin Islands
From 2013 to 2015, the Water & Power Authority in the Virgin Islands submitted six measurements for chromium-6, with three detecting chromium-6 above the reporting level of 0.03 µg/L. The highest detected concentration was 0.089 µg/L, and the median of detections was 0.072 µg/L. These figures show the presence of chromium-6 as measured, not a violation or health-based exceedance. Similarly, total chromium was detected at low levels far below the 100 µg/L federal MCL. These results indicate chromium-6 presence but do not establish individual water quality for any household.
Understanding 'Detected', 'Median', and 'Range' in Sampling Records
'Detected' means the measurement instrument found chromium-6 at or above its reporting limit; it does not imply a problem. The 'median' is the middle value of detected results, showing a typical concentration when present. The 'range' shows the lowest to highest detected values across all samples taken. Together, these terms describe the extent of chromium-6 in the sampled public water system, not a single home's water condition.
If your household equipment has failed and you are concerned about chromium-6, the next step is to order a detailed water test of your specific water supply. This test can identify your water’s chromium-6 concentration accurately. With those results, you can confidently select a treatment approach.
The Fleck Chromium-6 Filter ships ready to configure for home use. It is designed to treat chromium(VI) using ion exchange technology proven effective for this purpose. When combined with your test results, it can provide a tailored solution to address chromium-6 concerns in residential water.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-08-16. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Water & Power Auth. (St. Croix) (VI0000097), VI: 14 results across 2 listed contaminants, 6 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L