The water serving Oyster Bay in Nassau County primarily comes from groundwater sources managed by the Jericho Water District, which provides water to about 58,000 residents through over 18,000 connections. Government sampling under the EPA's Unregulated Contaminant Monitoring Rule (UCMR3) conducted between 2014 and 2015 recorded multiple detections of chromium-6, also known as hexavalent chromium or chromium(VI), within this system. These measurements offer a snapshot of what can be present in the local water supply, but individual household water may vary and requires separate testing.
If you see only total chromium results reported, why does that not fully answer concerns about chromium-6?
Total chromium measurements combine all forms of chromium present but do not distinguish between the hexavalent form and trivalent chromium. This distinction matters because chromium-6 (hexavalent chromium) differs chemically and behaviorally from chromium(III). The EPA's total chromium maximum contaminant level (MCL) is 100 micrograms per liter (µg/L or ppb), which is much higher than any chromium-6 levels detected in this area. Therefore, total chromium alone does not specify the chromium-6 fraction or its potential contribution to water characteristics.
If the UCMR3 survey was done system-wide, what can it tell you about your home's water?
The UCMR3 survey aimed to understand the occurrence of chromium-6 and other unregulated contaminants at a system level rather than individual residence levels. Sampling in the Jericho Water District found chromium-6 in 43 out of 50 samples, with a highest detected level of 1.3 µg/L and a median detection at 0.39 µg/L. Since these are detections—not regulatory violations—they provide background information. To know chromium-6 levels in your household water, a certified laboratory test on your specific tap water is necessary.
If you consider sample depth, well depth, or source type, how might chromium-6 levels vary?
Chromium-6 concentrations can differ depending on whether water is drawn from deeper wells, shallow wells, or different points in the distribution system. Groundwater chemistry is affected by geological factors, redox conditions, and contact with various minerals. The Jericho Water District's groundwater source, feeding the Oyster Bay system, reflects these influences. However, without testing your own water at the tap, it's not possible to precisely determine how these factors impact chromium-6 levels in your home.
If you receive a certified lab report for chromium-6, how should you interpret it?
Lab reports for chromium-6 list concentrations commonly in micrograms per liter (µg/L) or parts per billion (ppb). Understanding these units and comparing them to federal guidelines and documented occurrences can help inform your assessment. Since no federal maximum contaminant level exists specifically for chromium-6, these results are contextualized against monitoring data and total chromium standards. If chromium-6 is detected, consider its magnitude relative to local ranges from authoritative data.
If chromium-6 can change oxidation states, what does that mean for water quality from source to tap?
Chromium in groundwater can exist as trivalent chromium (Cr(III)) or hexavalent chromium (Cr(VI)). These forms differ in toxicity and behavior. Chemical changes can occur along the path from well water to the distribution system and finally to the tap, depending on water chemistry conditions such as pH and redox potential. This means chromium speciation may not remain constant, further complicating reliance on total chromium data alone.
If the highest measured chromium-6 level and median detection are well below total chromium standards, what does that clarify?
The highest chromium-6 detection in the Jericho Water District was 1.3 µg/L, much lower than the 100 µg/L federal total chromium MCL. This difference illustrates that the presence of chromium-6 at these levels is within a range observed in monitored public systems without direct regulatory limits for hexavalent chromium. It is important to avoid drawing conclusions about safety solely from occurrence data; these measurements are not violations or safety determinations.
What should you not conclude from regional chromium-6 data? Regional occurrence data describe the water system but do not establish the specific concentration or safety of your household water. Detection is not the same as a violation or unsafe condition. Regulatory limits exist for total chromium but not specifically for chromium-6. To fully understand your home's water quality and whether it aligns with your expectations or needs, a certified water test targeting chromium-6 is recommended.
For households finding existing water treatment unable to keep up with chromium-6 concerns, Pentek Chromium-6 Filter ships ready to configure directly. It offers a proven approach to address chromium-6 presence, complementing your current setup by targeting this constituent specifically.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-10-06. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Jericho Water District (NY2902831), NY: 100 results across 2 listed contaminants, 83 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L
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