Radium is a naturally occurring radioactive element that dissolves into groundwater as water moves through uranium- and thorium-bearing rock and soil. In Central Florida, where the Upper Floridan Aquifer supplies drinking water to millions of residents through utilities including OUC, KUA, and Toho Water Authority, radium enters the water supply from limestone and phosphate-bearing geological formations deep underground. The U.S. Environmental Protection Agency sets a Maximum Contaminant Level of 5 picocuries per liter (pCi/L) for combined radium-226 and radium-228 in public drinking water, established under the Radionuclides Rule. Municipal water suppliers are required to test for radium and report results in their annual Consumer Confidence Reports. On private wells, no such testing requirement exists. Central Florida homeowners, particularly those on private wells drawing from the Floridan Aquifer, may face radium exposure that goes untested without proactive water testing.
Where does radium in Florida tap water come from?
Radium is part of the natural radioactive decay chain of uranium and thorium, both of which are present in the rock and soil throughout Florida. As groundwater moves through the Floridan Aquifer, a massive limestone formation underlying virtually all of Florida and extending into adjacent states, it dissolves trace quantities of radium from the surrounding geology.
Florida's geology makes radium occurrence particularly relevant here. The state sits atop extensive phosphate deposits, and phosphate rock naturally contains elevated concentrations of uranium and radium. Central Florida's phosphate belt runs through Polk, Hillsborough, Manatee, Hardee, and DeSoto Counties, and the mineral influence of these formations extends into the broader aquifer system that supplies the Kissimmee-Orlando metro area. The Florida Department of Environmental Protection specifically identifies phosphate-rich soils and rock as a source pathway for radionuclide contamination in Florida drinking water (Florida DEP, Radionuclide Contamination).
Two isotopes are regulated together: radium-226, with a half-life of about 1,600 years, and radium-228, with a half-life of about 5.75 years. Both occur naturally in Floridan Aquifer water at varying concentrations depending on the depth of the wellfield and local geology. Deeper wells drawing from the Lower Floridan Aquifer tend to encounter higher radium concentrations than shallower upper aquifer wells.
What is the EPA limit for radium in drinking water?
The EPA's Maximum Contaminant Level for combined radium-226 and radium-228 is 5 picocuries per liter. The gross alpha particle activity MCL, which includes radium-226, is 15 pCi/L. These limits appear in the National Primary Drinking Water Regulations under the Radionuclides Rule (epa.gov/dwreginfo/radionuclides-rule).
A picocurie is a unit of radioactivity equal to one trillionth of a curie. At the 5 pCi/L MCL, the EPA's maximum contaminant level goal (MCLG) is zero, meaning there is no established safe threshold for radium exposure from a pure health standpoint. The MCL of 5 pCi/L represents the level at which treatment is both technically feasible and cost-effective for public water systems to achieve, not a threshold below which no health risk exists.
Long-term consumption of water with radium above the MCL is associated with increased cancer risk. Radium accumulates in bone tissue, where its radioactive decay can damage bone marrow and surrounding cells. The EPA states that people who drink water containing radium-226 or radium-228 in excess of the MCL over many years may have an increased risk of cancer.
Do Central Florida utilities test for radium?
Yes. All community water systems in Florida serving more than 25 people year-round are required to test for radionuclides under both EPA and Florida DEP regulations. Florida DEP is the primacy agency responsible for enforcing the Safe Drinking Water Act in Florida and requires regulated systems to report radionuclide test results in annual Consumer Confidence Reports.
The Florida DEP Annual Compliance Report for calendar year 2024 documents that Florida did have some violations of the gross alpha MCL, uranium MCL, or combined radium MCL during that reporting period. The majority of these violations occur in smaller community systems and not in the large municipal utilities serving the Orlando-Kissimmee metro area. However, the CCR for your specific utility and service address is the primary source for your household's actual data.
| Contaminant | EPA MCL | How to find your data |
|---|---|---|
| Combined radium-226 and radium-228 | 5 pCi/L | Your utility's annual Consumer Confidence Report |
| Gross alpha (excluding radon and uranium) | 15 pCi/L | Your utility's annual Consumer Confidence Report |
| Uranium | 30 micrograms per liter | Your utility's annual Consumer Confidence Report |
To look up your utility's CCR for Central Florida: OUC (Orlando) at ouc.com/environment-community/water/water-quality; KUA (Kissimmee) at kua.com/residential/water-quality; Toho Water Authority (St. Cloud, Osceola County) at tohowater.com/our-water/water-quality-reports; or search all Florida utilities through the Florida DEP CCR portal.
The CCR will list radionuclide test results in a table alongside other regulated contaminants. Look for the "Radioactive Contaminants" section and compare reported levels to the MCL column. If a utility has not detected a contaminant above a reporting threshold, it may note "ND" (non-detect) or report results below the detection limit.
For context on how to read your Florida CCR, including what the regulated contaminant tables mean and where to find radionuclide results, see the guide to reading Florida water quality reports.
Is radium in Florida well water a concern?
For homeowners on private wells, radium is a more significant consideration than for most municipal customers. No federal law requires private well owners to test their water, and Florida does not mandate routine radionuclide testing of private wells. This means private well water in Central Florida can contain radium at any concentration, including above the 5 pCi/L MCL, without triggering any regulatory notification.
Research on Florida groundwater confirms this concern. A study published in the National Institutes of Health's PubMed Central database (PMC6572226) documenting natural radiation in southern Florida found radium levels in some domestic self-supply wells in Sarasota County reaching 29 pCi/L, nearly six times the EPA MCL. A single location in Lee County recorded 50 pCi/L. These readings occurred in wells drawing from intermediate aquifer zones. While the Upper Floridan Aquifer supplying most Central Florida private wells typically shows lower concentrations, the Florida DEP explicitly notes that some areas of the state are susceptible to radionuclide contamination from phosphate-bearing geology.
For Central Florida well owners in Osceola County, south Orange County, and rural Polk County, radium testing is a reasonable precaution, particularly for wells at greater depth. This is especially relevant near historical phosphate mining areas. The well water quality guide for Kissimmee and Orlando covers the broader range of contaminants in Floridan Aquifer private wells, including iron, manganese, hydrogen sulfide, and hardness. The hydrogen sulfide guide for Central Florida wells covers the closely related issue of gaseous contaminants in the same aquifer zones.
How do you test for radium in tap water?
Standard water hardness and whole-home water quality panels do not include radium. Radium requires laboratory analysis using radiochemical methods, reported in picocuries per liter.
For municipal water customers, the simplest approach is reading your utility's current Consumer Confidence Report, which includes radionuclide monitoring results. The CCR is published annually, typically by July 1 for the prior calendar year.
For private well owners, contact a Florida-certified water testing laboratory and request a radionuclide panel covering radium-226, radium-228, gross alpha, and uranium. The Florida DEP maintains a list of certified laboratories. When you schedule a free water test through Pure Agua, our technician can discuss laboratory radionuclide testing for your specific address if your well chemistry or location indicates elevated risk.
Schedule your free water test to discuss radionuclide testing options for your address.
What removes radium from drinking water at home?
The EPA recognizes reverse osmosis as an effective technology for reducing radium in drinking water at the point of use. A certified reverse osmosis system typically achieves greater than 90 percent reduction of dissolved radium, alongside similar reductions for uranium, nitrates, PFAS, and other dissolved contaminants.
Standard activated carbon filtration does not significantly reduce radium. Ion exchange resins used in water softeners can reduce some radium, but softeners are designed for calcium and magnesium removal, and their radium reduction is variable and not reliable as a primary treatment strategy. For verified radium reduction at the drinking tap, a certified under-sink reverse osmosis unit is the appropriate technology.
For households concerned about radium, the most effective setup combines a whole-home system (addressing Central Florida's hard water and chloramine disinfection byproducts at every fixture) with an under-sink RO unit that handles radium and trace dissolved contaminants specifically in drinking and cooking water.
For well water addresses, addressing radium is part of a broader treatment plan that typically also covers iron and manganese removal and pH adjustment. The reverse osmosis stage at the drinking tap is the final step in a well treatment stack. For PFAS, which shares a treatment pathway with radium through reverse osmosis, see the PFAS in Central Florida drinking water article. Radium overlaps conceptually with the broader discussion of regulated contaminants covered in the disinfection byproducts guide for Central Florida tap water.
To understand what is in your tap water or well water, including radionuclides, contact Pure Agua to schedule a free water test at your address. We serve Orange, Osceola, and surrounding Central Florida counties.
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