What is Radium, combined (-226 and -228)* and Why Does It Matter?

Radium is a naturally occurring radioactive metal that forms deep in the earth as uranium and thorium slowly break down over millions of years. It seeps into groundwater through rock and soil, which means it shows up most often in wells and water systems that draw from underground aquifers. You can't see it, smell it, or taste it — and that's exactly what makes it worth paying attention to.

The health risks from radium aren't about a single glass of water. They build up over years of daily exposure. Once ingested, radium behaves like calcium in the body. Your bones absorb it and hold onto it. Over time, that stored radiation damages surrounding tissue. The International Agency for Research on Cancer (IARC) classifies radium as a Group 1 carcinogen — meaning there is strong evidence it causes cancer in humans. Long-term exposure is linked to bone cancer, leukemia, and other blood cancers. The risk rises with the amount you're exposed to and how long that exposure continues.

Right now, the EPA's legal limit for combined radium-226 and radium-228 is 5 picocuries per liter (pCi/L). That standard hasn't been updated since 1976. The Environmental Working Group (EWG) sets its own health guideline at just 0.05 pCi/L — 100 times stricter — based on current cancer risk models. Here's the problem: the data shows that 2,697 out of 2,764 water systems with detectable radium are already above the EWG guideline. The average detected level across those systems is 0.733 pCi/L. One system recorded a peak of 15.84 pCi/L — more than three times the EPA's legal limit. In other words, most systems are technically "legal" while still exceeding the level scientists consider safe.

Radium is not evenly distributed across the country. Illinois leads with 334 affected water systems, followed closely by Texas with 332. New York has 182 affected systems, Oklahoma has 167, and Colorado has 123. These states share something in common: geology. Illinois and parts of the Midwest sit above ancient sedimentary rock formations rich in naturally occurring radioactive materials. Texas and Oklahoma draw heavily from deep aquifers where uranium-bearing rock is common. Colorado's Rocky Mountain geology brings its own radioactive mineral deposits. If your water comes from a deep well or a system that taps into groundwater in any of these states, radium is worth testing for specifically.

The good news is that radium is highly treatable. Reverse osmosis (RO) filtration removes up to 95–99% of radium from drinking water, making it one of the most effective options available for home use. Ion exchange systems — the same technology used in water softeners — can also reduce radium significantly, though they work differently and need regular maintenance to stay effective. Simple carbon filters, like standard pitcher filters, do not remove radium. If you're in a high-risk state or your water comes from a well, it's worth getting your water tested before choosing a filter. An Echo Water reverse osmosis system is designed specifically to address contaminants like radium that standard filtration misses. Knowing what's in your water is the first step — and from there, the solution is straightforward.

Regulatory Standards for Radium, combined (-226 and -228)*

Cities With the Highest Radium, combined (-226 and -228)* Levels

States Most Affected by Radium, combined (-226 and -228)*

Frequently Asked Questions

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