Radon is a decay product of uranium or thorium, which is quite often found in groundwater. It is a colorless, odorless, and tasteless radioactive gas but is quite dangerous. Research on the impact of this element on humans began relatively recently, as did the introduction of any regulations regarding its concentrations in water. In Europe and the USA, the first studies started 35 years ago, while in the post-Soviet space, they began 20 years ago.

Radon can seep through cracks in the ground into buildings, dissolve in underground well and borehole water, and then enter human lungs and stomach. According to the World Health Organization (WHO), radon causes between 3% and 14% of all lung cancer cases, depending on its prevalence in soil, water, and other environmental factors.

Tissue damage occurs through direct exposure to alpha radiation, which is relatively shallow, causing oncological diseases precisely at the point of contact.

Today, we will discuss how radon contaminates water, its impact on human health, and the safety of therapeutic radon baths.

Where does radon in water come from?

Radon enters water and air from underground layers of the Earth that contain deposits of radioactive ores.

It is found exclusively in groundwater: wells, boreholes, and natural springs. Water from surface sources (rivers, reservoirs) contains almost no radon, as it escapes into the air before reaching the final consumer.

The dangers of radon in water supply systems include:

• Radon is a gas that tends to escape from water, saturate indoor air, enter the respiratory system, and contribute to lung cancer.
• Drinking radon-contaminated water directly affects the gastrointestinal tract, leading to stomach cancer.

According to an assessment by the U.S. National Academy of Sciences, cited by the Environmental Protection Agency (EPA), radon in drinking water causes approximately 168 fatal cancer cases per year (89% lung cancer and 11% stomach cancer). However, this figure is relatively low compared to the estimated 20,000 deaths annually from inhaling radon in residential buildings. WHO does not consider radon water consumption a major threat.

Radon levels in water are measured not in milligrams per liter, but in radiation units. The total radiation background of water should not exceed 0.1 Bq/L for alpha radiation and 1 Bq/L for beta radiation, including all radioactive elements. These parameters must comply with drinking water quality criteria.

Radon waters in Ukraine

In Ukraine, the problem of radon in water is hardly addressed, as there is no known solution. For example, the Kirovohrad region lies on the Ukrainian Crystalline Shield, which contains unique uranium deposits, and consequently radon, which seeps into groundwater. Increased radionuclide levels are found in both soil and natural water sources. Studies from 2013-2014 on decentralized water supply sources (wells and boreholes) showed radon levels reaching 654.1 Bq/L (compared to the established limit of 100 Bq/L; in the U.S., this standard varies between 10 and 150 Bq/L depending on the state). According to WHO recommendations, the levels of each radionuclide should be measured separately. However, monitoring is currently almost nonexistent.

Based on the geological map of radioactive rock deposits, all regions of Ukraine, except for the southern (Crimean-Black Sea depression) and eastern-northern parts (Dnieper-Donets depression, Donetsk fold area), have uranium potential. The highest radon levels are in Central Ukraine, particularly in regions located on the Ukrainian Shield: Zhytomyr, parts of Rivne, Kyiv, Vinnytsia, parts of Khmelnytskyi, Cherkasy, Kirovohrad, Dnipropetrovsk, and Zaporizhzhia. According to data from the National Cancer Institute, these regions rank among the most problematic in terms of oncological diseases, with Kirovohrad leading the list.

Water treatment for radon removal

Removing radon from water is a relatively simple technological task, with two primary methods:

1. Adsorption using activated carbon and other sorbents
2. Aeration

Activated carbon filtration

Filtering radon-contaminated water using activated carbon is the most budget-friendly method, involving the installation of standard carbon filters in tank or cartridge form. The principle of these systems is that water passes through a material layer, which removes impurities such as radon, chlorine, and organic substances before entering the pipeline. Once the filter medium is exhausted, it is either washed and discharged into the sewer or replaced entirely.

This method is suitable for whole-house underground water treatment and drinking water purification systems. However, a significant drawback is that activated carbon can accumulate radiation and become a carrier of radioactive contamination.

Aeration

Aeration involves passing air bubbles through a water column, which carries radon away through ventilation, dispersing it into the atmosphere at safe concentrations.

This method does not produce radioactive byproducts and is mainly used at large water treatment plants (in the USA, household-wide aeration systems are also common). The primary downside is its high cost.

Radon therapy

Despite the recognized health risks associated with radon exposure, radon water is used in alternative medicine. Science remains divided on this method, but radon spa resorts have been operating since the 19th century and continue to function today. Popular radon resorts can be found in Serbia, Hungary, the Czech Republic, Germany, Croatia, Japan, Greece, and China. Ukraine also has several such resorts, such as Khmilnyk in Vinnytsia region. While the U.S. has a skeptical stance toward radon therapy, some insurance companies in Austria and Germany include it in coverage plans. In Japan, researchers actively investigate side effects but continue using radon baths.

There are two main applications of this alternative therapy:

1. Radon baths or pools – According to existing data, these help reduce pain and inflammation in musculoskeletal disorders such as arthritis, nerve-related pain syndromes, endocrine disorders, psoriasis, and autoimmune diseases.
2. Drinking radon water – Less common and primarily recommended for gastrointestinal disorders.

There are few comprehensive clinical studies on the subject, likely due to its specific nature and potential hazards. However, some materials exist.

One of the most popular areas of application is arthritis therapy. A study involving 60 participants showed that while pain reduction was similar between those receiving standard treatments with or without radon, long-term effects differed—patients exposed to radon baths reported prolonged relief. A summary of research on musculoskeletal diseases confirms the effectiveness of radon therapy, though no long-term systematic studies on its delayed effects exist.

Animal studies on gout, colitis, and atopic dermatitis following radon gas inhalation or radon water consumption have demonstrated positive effects attributed to the gas’s antioxidant properties. However, findings from mice do not always translate to humans, and the scientific community remains uncertain about the benefits of radon water.

Radon gas is also being explored as a potential adjunct therapy in cancer treatment, though no clinical trials exist.

Radon water: Benefits and risks

Radon water, which contains the radioactive gas radon, may possess therapeutic properties and is potentially used for treating various conditions through bathing procedures. However, long-term exposure carries radiation risks. Continuous consumption of high-radon water can have severe health consequences. Before using radon water for therapeutic purposes, it is crucial to consult a medical specialist, given the scientific uncertainty regarding its efficacy and safety.

Resources:

1. Basic Information about Radon in Drinking Water – U.S. Environmental Protection Agency
2. Water Consumed by the Population of Our Region – Kirovohrad Regional Public Health Center
3. Bulletin of Taras Shevchenko National University of Kyiv. Geology
4. Cancer in Ukraine 2020-2021 – Incidence, Mortality, and Oncology Service Performance Indicators
5. A. Franke, L. Reiner, H. G. Pratzel, T. Franke, K. L. Resch, Long‐term efficacy of radon spa therapy in rheumatoid arthritis—a randomized, sham‐controlled study and follow‐up, Rheumatology, Volume 39, Issue 8, August 2000, Pages 894–902. 
6. Falkenbach, A., Kovacs, J., Franke, A. et al. Radon therapy for the treatment of rheumatic diseases—review and meta-analysis of controlled clinical trials. Rheumatol Int 25, 205–210 (2005). 
7. Mareyuki Takahashi, Shuji Kojima "Suppression of Atopic Dermatitis and Tumor Metastasis in Mice by Small Amounts of Radon," Radiation Research, 165(3), 337-342, (1 March 2006) 
8. Yuichi Nishiyama, Takahiro Kataoka, Keiko Yamato, Takehito Taguchi, Kiyonori Yamaoka, "Suppression of Dextran Sulfate Sodium-Induced Colitis in Mice by Radon Inhalation", Mediators of Inflammation, vol. 2012, Article ID 239617, 11 pages, 2012. 
9. Reo Etani, Takahiro Kataoka, Norie Kanzaki, Akihiro Sakoda, Hiroshi Tanaka, Yuu Ishimori, Fumihiro Mitsunobu, Kiyonori Yamaoka, Difference in the action mechanism of radon inhalation and radon hot spring water drinking in suppression of hyperuricemia in mice, Journal of Radiation Research, Volume 57, Issue 3, June 2016, Pages 250–257 
10. Kojima S, Cuttler JM, Inoguchi K, Yorozu K, Horii T, Shimura N, Koga H, Murata A. Radon Therapy Is Very Promising as a Primary or an Adjuvant Treatment for Different Types of Cancers: 4 Case Reports.