Tens of thousands of people from all over the former Soviet Union come to one resort town in Ukraine every year — but it isn’t the pine forest or the fresh air that bring them here.

They come for the radon.

You probably know radon as a radioactive gas that causes lung cancer. But in Ukraine, people take baths in groundwater that’s naturally rich in the element to treat back injuries, arthritis, skin rashes, infertility and a host of other medical conditions. The eight sanatoriums in the town of Khmilnyk treat around 50,000 patients annually, and all but one receive some public funding to do it.

“I was paralyzed from the waist down. For five months, I didn’t get up off the bed. I could move my toes but I couldn’t stand up,” says Victor Pedanuk, a 65-year-old economist who turned to radon after surviving a car accident. “Here in 10 days, they put me back on my feet.”

He added that his ears were ringing all the time for three years after the accident until he received therapy in a radon pool. After that, the ringing just stopped.

“This is happiness,” he says.

Aleksandr Fiks, assistant medical chief of JD Sanatorium, explains that when dissolved in water, radon enters the body through the skin, gets into blood vessels and spreads through the body.

“It’s been proven that radon causes blood vessels to expand. It decreases inflammation, and lowers pain; it is also anti-allergic. It also decreases the inflammation in the nerves, so we can also treat the nervous system,” he says.

He checks off a list of health issues he claims radon can treat: spine and joint problems like arthritis and rheumatism, prostate and urinary problems, high blood pressure, even infertility.

Dr. Ludmila Bevz, the medical director at the nearby Radon Sanatorium, says the baths also help patients with diabetes, obesity and migraines. She says radon baths deepen sleep, increase work productivity, slow the heart rate, lower cholesterol and help regulate the menstrual cycle. And she seconded the fertility theory.

“I have seen about three couples who had been treated for infertility for years, and after the radon baths they were able to have children,” she says.

The patients take radon baths on alternating days, and remain in the bathwater for between 15 and 35 minutes, “because that’s what’s proven to be the optimal period,” Fiks says. He explains that the concentration of radon in bathwater is between 25 and 35 nanocuries per liter.

“In the concentrations we have here, it’s proven in the clinical and human studies that it cannot cause cancer. It’s a low dose,” Fiks says.

Radon forms naturally when radioactive metals like uranium, thorium, or radium break down in rocks, soil or groundwater. According to the US Centers for Disease Control: "People can be exposed to radon primarily from breathing radon in air that comes through cracks and gaps in buildings and homes. Because radon comes naturally from the earth, people are always exposed to it."

But Bill Field, a radon expert from the University of Iowa, says that no exposure to radon is safe. Even if radon is dissolved in the water, most of it is inhaled, rather than absorbed through the skin.

“Within a couple of minutes, half the radon in the water will diffuse into the air,” Field says. “Once the gas diffuses out, it creates the decay products that cause the majority of the lung cancers. I wouldn’t want to be in a room where there are 25 to 35 nanocuries per liter of radon.”

While it’s possible that radon might have some medical benefits — Field has seen studies showing some immune system impacts from radon — he says patients should be warned about the dangers involved in such treatment.

“Anyone getting into these baths surely increases the risks of developing lung cancer,” he says. “I would urge someone to consider the traditional methods of treatment before radon baths.”

Still, Field is eager to communicate with doctors and scientists from ex-Soviet countries about radon therapy.

“I’m very interested in the beneficial effects,” he says. “If there is therapeutic value, I don’t think anyone knows what the mechanism is.”

None of this deters people from coming for radon treatment in Khmilnyk, where nobody is informing patients that radon is carcinogenic.

People pay hundreds of dollars to fly in from all the former Soviet Union republics. Russian-speaking migrants come from the United States, Canada, Israel and Germany, too. Arab patients have started arriving as well. A Kuwaiti man accompanied by 12 women recently visited and was so satisfied with the treatment that he wanted to reserve the entire sanatorium for Kuwaitis, Dr. Fiks said.

Doctors at Radon Sanatorium, which is currently building a second facility, keep a book on display signed by some of their high-profile patients. Among them are the names of the Argentine and South Korean ambassadors to Ukraine, popular singers, and athletes. Locals say a player from Ukraine’s national basketball team and a world rifle shooting champion also came for treatment.

It turns out radon therapy is not entirely unique to Ukraine. An old German spa has offered it for decades. And there's been research about the alternative treatment, including a study that compares radon therapy in the US state of Montana to Europe’s radon spas.

Spa visitors relax in a pool containing radon in the eastern German town of Schlema in January 2001. Credit: Reuters

But it’s remarkable how many people swarm to this little Ukrainian town for what they believe is top-notch therapeutic radiation.

Aren't radon baths dangerous? I thought so, until I heard that both of my grandparents, who are from the Soviet Union, were treated with radon decades ago. My grandfather Shlomo Masis is turning 100 in August. Neither he nor my 87-year-old grandmother, Sulamif Belenkaya, ever had cancer. (Although my grandmother, who was treated for arthritis, says that the baths didn’t help her and she eventually had to get knee surgery.)

But Field says my grandparents can’t prove that radon baths are safe.

“There are lots of people from Hiroshima who never developed cancer,” he says. “It’s just a matter of chance.”

He adds that radon gas is more dangerous at home, where people spend most of their time, than in a spa a person might visit only for 30 minutes a session, a few times per year.

“The good thing about the baths,” he says, “is that it’s not constant exposure. It’s short term.”

Journalist Julie Masis reported from Khmilnyk, Ukraine.