Cadmium in Well Water: The Public 0.005 mg/L Limit

By SubcontractorHub Editorial Team·Published October 2026

Cadmium in well water is easy to file under “metals” and then compare to the wrong number. Inorganic mercury, on the next conversation, is 0.002 mg/L, covered in mercury in well water. The column names themselves are MCL and MCLG. SubcontractorHub is an all-in-one sales and project management platform for solar, roofing, and HVAC contractors. The water note works the same way: one contaminant, one unit, no borrowed limit.

Cadmium in Well Water Is Its Own Row

The inorganic block lists cadmium between beryllium and chromium (total). The number beside it is not chromium's 0.1 and not mercury's 0.002. If the lab PDF has several metals, each line keeps its own public figure.

USGS lists cadmium among trace elements, which it defines as concentrations less than 1.0 milligram per liter, along with arsenic, chromium, copper, lead, mercury, nickel, and zinc. That definition explains why the number looks small. It does not replace the MCL. Chromium's row is chromium in well water.

The Public 0.005 mg/L Line, and Who It Governs

The National Primary Drinking Water Regulations apply to public water systems. On the inorganic table, cadmium is listed with an MCLG of 0.005 and an MCL of 0.005, in milligrams per liter.

Both columns match, the way they match on the mercury row, at a different number. An MCL is enforceable for public systems. An MCLG is the non-enforceable goal. Quoting 0.005 without saying which column, and without saying public, is how a kitchen-table note becomes a fake statute.

Private wells are outside that public program. Read private well water regulations before you tell someone a state has adopted 0.005. This page uses it as the public benchmark only.

Cadmium in Well Water When the Lab Uses Micrograms

The USGS Circular 1209 glossary says one thousand micrograms per liter equals 1 milligram per liter. 0.005 times 1,000 is 5. A report that says 5 µg/L is the same mass as 0.005 mg/L. A report that says 5 mg/L is not.

Convert with the microgram milligram converter and read the scale in milligrams and micrograms. Do not run cadmium through the nitrate factor or the nitrite factor. Those are different ions.

Galvanized Pipe Is a Source on the List, Not a Verdict

EPA's source list for cadmium includes corrosion of galvanized pipes, erosion of natural deposits, discharge from metal refineries, and runoff from waste batteries and paints. Galvanized pipe is the item a dealer can see in a basement. Seeing it does not prove it is the source of this sample.

A first-draw sample and a flushed sample answer different questions, the same way they do for lead. If you only have one bottle, say which tap and how long the water sat. Do not upgrade a single number into a plumbing diagnosis.

The effect EPA lists is kidney damage, for long-term exposure above the MCL. That is the table's phrase. It is not a diagnosis. This page is not medical advice. Mercury's row uses the same effect phrase at a different concentration. Do not merge the two talks.

What This Page Will Not Sell

The fetched cadmium row does not name a treatment. No softener, no reverse osmosis, no percent removed, no installed price. A proposal that needs a device has to cite that device's listing, not this article.

How a listing is read, standard by standard, is NSF/ANSI water treatment standards. A standard number is not a rank, and it does not silently include cadmium because the brochure says “metals.”

How to Write the Cadmium Line on the Job

Five fields keep the next reader from borrowing mercury's number.

1. The word cadmium, not “metals” and not mercury.
2. The number and the unit. 0.005 mg/L or 5 µg/L, with the scale named.
3. The public 0.005 mg/L figure, labeled public, not as a county statute.
4. Whether the sample was first-draw or flushed, and the tap.
5. The lab and the sample date. A sister metal on the same PDF stays on its own line.

What else belongs on the order is the well water testing guide. Cadmium does not replace bacteria or nitrate.

Who Should Ignore a Guess From This Page

A clinician answers a health question. A county page answers a county rule. A dealer can use this article to keep 0.005 mg/L attached to cadmium and off the mercury line. A dealer who needs a removal percent will not find one here.

Cadmium in Well Water When the Report Says ppm

EPA's note says milligrams per liter are equivalent to parts per million, unless the row notes a different unit. A lab line of 0.005 ppm matches the public 0.005 mg/L figure under that note. Leave the 1,000 factor for the microgram scale. Using it on a ppm number invents a different mass.

USGS says one thousand micrograms per liter equals 1 milligram per liter, and it describes micrograms per liter as one part per billion in most ground water. 0.005 mg/L is 5 µg/L on that scale. If the sheet says 5 ppb, write 5 µg/L next to it and name the glossary. Do not treat a bare 5 as either scale.

Cadmium in Well Water Next to the Other Metal Rows

The same inorganic table holds other numbers. Inorganic mercury is 0.002 mg/L in both columns. Chromium (total) is 0.1 mg/L in both. Cadmium is 0.005 mg/L in both.

They share a page. They do not share a limit. A quote that says “metals are 0.005” has already mixed the rows.

Kidney damage is the effect phrase on the cadmium row and on the mercury row. Allergic dermatitis is the effect phrase on chromium (total). The repeated words are not a reason to merge the talks. Read the row the lab named.

If the lab says 0.010 mg/L of cadmium, that figure is twice the public 0.005 mg/L line by division. If it says 0.002 mg/L of cadmium, that figure is below 0.005 on the same scale. Say public line both times. Do not say the county failed the well. This page did not open a county statute.

What Each Listed Source Is Allowed to Mean

EPA lists four sources for cadmium in drinking water. Corrosion of galvanized pipes is the one a dealer might see in a basement. Seeing the pipe does not prove this bottle came from that pipe. Erosion of natural deposits does not require a factory on the street.

Discharge from metal refineries, and runoff from waste batteries and paints, are the other two phrases on the row. Record them as the table's list. Do not pick the most familiar phrase and call it the cause of this sample.

The row still does not name a treatment. A softener, a carbon tank, and reverse osmosis are not written there. A quote that needs a device cites that device's listing. It does not cite this article for a removal percent, because no percent was fetched.

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