The public water system record for the Water & Power Authority in St. Thomas, Virgin Islands, reports detection of chromium-6 (hexavalent chromium) in its supply. Between February and November 2014, the Environmental Protection Agency’s Unregulated Contaminant Monitoring Rule 3 (UCMR3) recorded eight samples with four detections above the reporting level of 0.03 micrograms per liter (µg/L), or parts per billion (ppb). The highest measured chromium-6 level was 1.0 µg/L, with a median of detected values at 0.097 µg/L. These results reflect measurements for the entire system, not specific residential taps.
If you want to understand chromium's oxidation state changes from source through distribution to your tap
Chromium in water exists in multiple oxidation states. Hexavalent chromium (Cr(VI)) is one form that can change as water moves from the well or source, through the distribution network, and finally to your faucet. Factors such as the presence of oxygen and organic matter influence whether chromium remains in the hexavalent state or transitions to trivalent chromium (Cr(III)), which behaves differently chemically. This variation means that the chromium-6 concentrations recorded in system testing may not directly match what reaches your home tap. Testing your household water is necessary to determine your specific chromium-6 exposure.
If you consider the types of chromium-6 sources in the Virgin Islands environment
Hexavalent chromium may originate from natural (geogenic) sources or from industrial activities such as metal plating. In the Virgin Islands, the geological formations are often influenced by ocean proximity, and while local industrial chromium discharge is limited, natural rock compositions can contribute hexavalent chromium to groundwater. Distinguishing between geogenic and industrial chromium sources is useful for understanding fluctuations in measured levels and for selecting appropriate treatment approaches.
If you want to know about seasonal or multi-year fluctuations in chromium-6 in the Virgin Islands' water system
The EPA’s UCMR3 data covering 2013-2015 show chromium-6 sampled over several months in 2014. These single-year snapshots capture some variability but do not describe long-term trends. Seasonal changes in rainfall, temperature, and water demand can affect chromium speciation and concentration. Because water quality may vary over time, periodic monitoring is advisable to inform treatment decisions rather than relying solely on historic system records.
If you want to identify which household fixtures or appliances might be affected by chromium-6 first
Hexavalent chromium can interact differently with various water-using fixtures. Devices with internal components that encourage oxidation/reduction reactions, such as water heaters or appliances with metal parts, may see changes in chromium speciation locally. Faucets and drinking water outlets represent direct exposure points. Awareness of usage patterns and fixture types helps in targeting treatment where it is most beneficial for reducing chromium-6 intake.
If you want to understand how your home's plumbing materials and age might influence chromium-6 levels at the tap
Plumbing materials such as copper, galvanized steel, or plastic can affect the chemical environment inside household pipes. Older plumbing may foster conditions altering chromium speciation or attaching chromium species to pipe surfaces. This can lead to differences between system water quality reports and what actually flows from your tap. A water test that samples after your home plumbing is necessary for clarity.
If you are curious about aesthetic secondary standards compared to health-based limits for chromium-6
The public water system record notes no EPA health-based violations for chromium-6 or total chromium. While there are federal Maximum Contaminant Levels (MCL) for total chromium at 100 µg/L, no federal MCL exists specifically for hexavalent chromium. Secondary standards address factors like taste, staining, or corrosivity and do not indicate health risk. Understanding these distinctions helps in evaluating your water’s characteristics and the need for treatment focused on chromium-6.
Given the data from the Water & Power Authority system serving St. Thomas, Virgin Islands, households considering treatment should start with testing of their own water to identify the actual chromium-6 concentration at the tap. For homes with measured hexavalent chromium, technologies designed specifically for chromium(VI) address this constituent effectively. One such technology is the Fleck Chromium-6 Filter, which ships ready to configure for residential use. This solution targets chromium-6, providing an option when treatment is determined necessary based on household water quality.
The government’s UCMR3 record represents measurements for the entire public water system, not individual household conditions. For more detailed information, the Environmental Protection Agency’s official public water data is the authoritative source on chromium-6 occurrences in the Virgin Islands water supply.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-11-05. 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. Thomas) (VI0000443), VI: 16 results across 2 listed contaminants, 8 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L
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