Radium is the one contaminant in this series that makes a Geiger counter click. Radium-226 and radium-228 are radioactive isotopes — real radiation, right in the glass — and they show up in drinking water more often than most people realize. No taste, no smell, no color. You cannot sense it. Only a lab test finds it.
So let’s talk about it straight: what it is, where it comes from, and what the risk actually looks like at the levels people drink.
What it is
Radium is a naturally occurring radioactive metal. It’s born when uranium and thorium — both present in small amounts in most rocks and soil — undergo radioactive decay. Two of its isotopes matter for drinking water: radium-226 and radium-228.
Here’s the detail that matters for your body: radium behaves chemically a lot like calcium. When you drink it, your body mistakes it for calcium and deposits it in your bones, where it sits and emits radiation into the surrounding bone tissue. That’s why the health concern is specifically bone cancer — along with other cancers linked to long-term exposure.
A quick framing note, since this series covers carcinogens: IARC (the International Agency for Research on Cancer) lists both radium-226 and radium-228 as Group 1 — “carcinogenic to humans.” That classification is about hazard: it says radium can cause cancer. It does not say how much risk a given exposure carries. Group 1 does not mean “dangerous at any dose.”
Where it comes from
Erosion of natural deposits — it’s geology, not industry. Deep wells pull from rock formations where radium dissolves into the water over time. Surface water and shallow wells typically have lower levels; deep wells have higher ones. Oil and gas extraction activities can also elevate concentrations in some areas.
This isn’t a rare edge case. USGS research found that in some regions — including the mid-continental U.S. and the North Atlantic coastal region, which includes parts of New Jersey — more than 20 percent of sampled wells had radium above the federal limit. If you’re on a private well in one of those regions, radium is not a hypothetical; it’s a routine test.
The health picture, honestly
The EPA’s numbers, plainly: the maximum contaminant level (MCL) for combined radium-226/228 is 5 picocuries per liter (pCi/L), and the health goal (MCLG) is zero — EPA doesn’t consider any level risk-free, just legally acceptable below the limit.
What does the legal limit mean in real risk? EPA estimates that 1 in every 10,000 people drinking water at the MCL for a lifetime would develop cancer. That’s the honest math: a real, nonzero risk, but not a large one at the legal limit. California, for reference, set its public health goal vastly lower — 0.05 pCi/L for radium-226 and 0.019 pCi/L for radium-228 — levels so low most lab tests can’t even detect them.
The risk scales with dose and time. A little above the limit for a year is a different story than five times the limit for twenty years. This is a long-term-exposure problem, not an acute-poisoning one.
How to test
There is no home strip for radioactivity. Radium is measured in picocuries per liter — a radioactivity measurement, not a chemical one — and it takes a lab. Most people test two ways:
- Gross alpha screening. Labs often start here: a general screen for radioactive particles. If gross alpha comes back elevated, you follow up with radium-specific analysis.
- Radium-226/228 analysis. The exact measurement the EPA limit is based on.
In New Jersey, radium screening is built into the process: the state’s Private Well Testing Act requires a gross alpha test when a property with a private well changes hands, so if you bought a house on well water here, you may already have a number on file. Either way, a certified lab is the only way to know your level. Utilities on public water are required to test for it, and the results are in your annual water quality report — check it before paying for anything.
What actually removes it
The good news: radium is one of the more straightforward contaminants to remove, because as an ion it responds to proven methods. Per the WQA fact sheet and EPA guidance:
- Cation exchange (a whole-house water softener). This is the standout: a standard ion-exchange softener removes radium the same way it removes calcium and magnesium — it’s all the same exchange process. One of the rare cases where “just a water softener” is a legitimate, proven treatment.
- Reverse osmosis. An under-sink RO unit removes radium from drinking and cooking water at the tap — solid choice if you only want to treat what you drink.
- Distillation and lime softening. Both effective, though distillation is slow and energy-hungry for household use, and lime softening is a utility-scale method.
What does NOT remove it
- Boiling. Does nothing for radium — if anything, boiling water down concentrates it as the water evaporates.
- Any carbon filter — pitcher, faucet, fridge, whole-house carbon block. Carbon does not remove dissolved radium ions. Zero effect.
- A sediment filter. Screens particles, not dissolved ions.
- UV sterilization. Kills microbes; does nothing about radioactivity.
- Chlorine or chlorination. Disinfects; doesn’t touch radium.
What I’d buy
Treatment type: a whole-house cation-exchange water softener — it’s one of the rare cases where the standard softener is the proven answer, treating every tap in the house for radium in one system. If you’d rather treat just your drinking water, an under-sink reverse osmosis unit is the proven point-of-use option. Either way, test first and confirm the treatment brought your combined radium-226/228 under the 5 pCi/L federal limit with a follow-up lab test.
The bottom line
Radium is invisible, tasteless, radioactive, and naturally in the ground — and it’s also one of the easier contaminants in this series to beat, because plain ion exchange works. The trap is never testing: the biggest risk isn’t the radium itself, it’s drinking it for decades without knowing. One lab test tells you where you stand. If you’re on a private well in radium country, that’s the single highest-value test you can run.
Start here: What’s In Your Water? — learn how to read your water report and test your own tap.
Leave a Reply