Chromium 6 Water Test: The Test With No Federal Limit
Your well report says chromium is under the limit, and
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Your well report says chromium is under the limit, and that may seem like the end of the story. It may not be, because the federal limit covers total chromium and says nothing specific about chromium-6.
Chromium-3 is needed in tiny amounts, while chromium-6 is the far more harmful industrial form. A passing total result cannot tell you how much of it is chromium-6, and a separate chromium-6 water test is the way to get that number.
At ETR Laboratories, we test for both total chromium and chromium-6. In this article, we explain what the federal limit covers, what a total result cannot show, and how the separate test works.
EPA sets 100 parts per billion (ppb) for total chromium, and that number includes chromium-6. No federal limit exists for chromium-6 on its own. EPA covers both forms under one number because they can convert into each other in water and in the body.
The limit applies to public water systems. Private wells fall outside the Safe Drinking Water Act, so for a well owner, no limit also means no routine testing unless you arrange it. That is why private well owners set their own testing schedule.
That shared number is also what lets chromium-6 slip past a routine panel.
A total chromium result adds every form together, so a number under 100 ppb says nothing about how much is chromium-6. Total chromium is commonly measured by ICP-MS (EPA Method 200.8), which reports the element, not the form.
The limits that apply and what public monitoring has found show how wide that blind spot can be.
The Limit Ladder: 100, 50, 10 and 0.02
Here is how the numbers compare, with California’s figures from the State Water Board.
| Level | Limit | What it covers | Status |
| EPA (federal) | 100 ppb | Total chromium, all forms | Enforceable for public water systems |
| California total chromium | 50 ppb | Total chromium, all forms | Enforceable |
| California chromium-6 | 10 ppb | Chromium-6 only (effective October 1, 2024) | Enforceable |
| California public health goal | 0.02 ppb | Chromium-6 only | Goal, not enforceable |
As an illustration only, and not a sample result, a total chromium result of 30 ppb passes both total limits. If most of that 30 ppb were chromium-6, it could still exceed California’s 10 ppb chromium-6 limit.
EPA’s 2013 to 2015 monitoring under UCMR 3 found chromium-6 at or above 0.03 micrograms per liter in 47,503 of 62,837 results (75.6 percent) and in 4,401 of 4,919 public water systems (89.5 percent). Total chromium topped 100 micrograms per liter in just one of 4,922 systems.
Those were public systems, not wells, and 0.03 is far below any state limit, so detected does not mean unsafe. Even so, it shows total chromium can pass while chromium-6 is present.
EPA’s final August 2024 assessment of hexavalent chromium concluded that it is likely to be carcinogenic to humans when ingested, based on animal studies.
EPA is expected to decide by August 2027, under a legal settlement, whether the total chromium standard needs revising. California is the only state with a confirmed, enforceable chromium-6 drinking water standard, so ask your state drinking water program about local rules.
A hexavalent chromium water test measures only that form, usually by ion chromatography followed by a color reaction. EPA Method 218.7 is the hexavalent chromium testing method for drinking water.
The method preserves each sample with a buffer that raises the pH above 8, so chromium-6 stays stable in the bottle, and it requires analysis within 14 days. Chlorine can also convert chromium-3 into chromium-6, so handling affects the result.
If your panel shows detectable total chromium, or your well sits on the geology described next, add a chromium-6 water test.
No federal chromium-6 limit exists to compare a private-well result against. Here are the three things to check first:
California’s enforceable 10 ppb limit works as a reference point, though it is a California public-water standard and not a federal rule for private wells. A ‘not detected’ result means the concentration was below what the lab can measure, which is not necessarily zero.
If you tested both, total chromium vs. hexavalent chromium results answer different questions and are not interchangeable. Unfamiliar terms on your report can be explained in our contaminant glossary.
Chromium-6 occurs naturally through the erosion of chromium deposits and can also come from industrial releases. A 2007 PNAS study found that chromium-3 in serpentinite rock can oxidize to chromium-6, and a Duke study of 376 North Carolina Piedmont drinking water wells found about 90 percent had detectable chromium-6 from natural leaching. Metal plating is among the industries that can affect well water in your state, so chromium-6 in well water can have either origin.
Here are the situations that call for the test:
Our Premium Well Water Test and Ultimate Well Water Test both list total chromium but not chromium-6, so the chromium-6 test is ordered separately. The panel you choose determines which contaminants the lab looks for, and chromium usually appears on a broader panel on a longer cycle. State testing requirements differ too.
A few quick answers follow.
California adopted a chromium-6 limit of 10 micrograms per liter, effective October 1, 2024, alongside its older total limit of 50 micrograms per liter. We could not confirm other states, so contact your state drinking water program.
The Chromium-6 (hexavalent) Water Test costs $50 at ETR Labs. Our panels list total chromium only, and every test comes with a free consultation with one of our experts.
Yes. Methods such as EPA 218.7 call for a buffered, pH-adjusted sample so chromium-6 does not convert. Use the bottle supplied with your kit and follow its instructions exactly.
Probably not at the levels that count. One water treatment retailer describes strips that read from 50 to 5,000 ppb, far above California’s 10 ppb, so a ‘none detected’ result would not show whether a well is under that limit.
No. Private wells fall outside the federal Safe Drinking Water Act, and no federal chromium-6 limit exists. EPA’s 100 ppb standard covers total chromium in public water systems. State rules can differ, so check with your state agency.
Yes. A total chromium result under 100 ppb can still include chromium-6, because the total test combines the forms and does not report chromium-6 separately. That doesn’t make a passing result unsafe; it just means the chromium-6 portion stays hidden until tested.
No. Boiling is not a chromium-removal method, and it can concentrate dissolved metals in the remaining water. If a test confirms chromium-6, a qualified water professional can recommend a treatment system suited to your well.
ETR Laboratories offers the Chromium-6 (hexavalent) Water Test for $50, and every test comes with a free consultation with one of our experts, who can help you read the result.
Our panels report total chromium only, and the Chromium Water Test is also $50 if you want that number on its own.
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