On the 67th anniversary of the bombing of Hiroshima, anti-nuclear organizations and concerned citizens staged a large protest of nuclear development in Los Alamos. Though protesters often cite political and ethical rationales, another common argument against nuclear power is the harmful radiation that can leak into local communities. But as sites such as Los Alamos National Laboratory receive high-profile attention, an invisible and potentially more dangerous source silently creeps into Santa Fe homes.

The culprit is radon—a colorless, odorless gas that is a by-product of uranium decay. Classified by the US Environmental Protection Agency as a group A carcinogen, radon studies have produced enough data to "demonstrate a casual association…with human cancer." According to the National Cancer Institute, it is the second leading cause of lung cancer in the US and the No. 1 cause of lung cancer in nonsmokers, responsible for as many as 22,000 deaths each year.

The number of homes currently affected in Santa Fe is undetermined, as neither the city nor state government requires radon testing in homes. However, the state Radiation Control Bureau has indicated that, while most of New Mexico presents a moderate risk for high radon levels, 32 percent of Santa Fe County homes fall into a higher-risk category. By contrast, in Los Alamos County—infamous for its nuclear activity—only 30 percent of homes are high-risk.

Santa Fe resident Bill Straub, a premise media consultant with Dex One, has personally seen the results of living in a radon-filled home. Both his sister and her husband died from lung cancer while living in Portland, Ore.—an area of the country the EPA deems similar to northern New Mexico in terms of potential radon exposure.

"My brother-in-law came down with lung cancer…and we buried him in the spring. In the fall, my sister got sick," Straub tells SFR.

"It struck me as a coincidence," Straub says of his family's cancers. "They both came down within a year, and exactly the same stage, same cancer, same location."

Straub's sister felt the same way and had their 20-year home tested for radon gas. She discovered high levels of radon coming into the house from the basement.

Indeed, radon gas generally enters homes through the soil under the house. "It's basically pressure-driven," KC Wester of Clean Sweep, LLC—the only certified residential radon mitigation provider in Santa Fe—tells SFR. "Generally speaking, inside of a home you've got a low pressure system, outside high pressure…Everything that's removing air has to [draw it] from someplace, and that's usually the soil."

Radon has a half-life of only 3.8 days, but it's constantly being drawn into homes via pressure differences—often created by common household appliances, which are capable of removing huge amounts of air. A typical clothes dryer, for example, can move 100 cubic feet of air per minute. The average fan above a stovetop exhausts as much as 300 CFPM. "It's the make-up air that drags in the radon gases," Wester explains. Once inside, humans are exposed through inhalation.

Straub says although his sister implemented mitigation techniques, "it was too late. She already had the cancer and ended up succumbing." She was 48 years old.

Radon gas itself, though radioactive, is not what causes cancer; it's the decayed product that does. When radon breaks down, it emits radiation in the form of alpha particles. These particles are relatively large and cause mutations in living tissue, specifically the lungs, which in turn can lead to cancerous cells.

Radon concentrations are measured in picocuries per liter of air. A home in a higher-risk category—4 pCi/L or above—is actually experiencing radiation levels equal to 35 times that which the Nuclear Regulatory Commission allows just outside the perimeter fence of a radioactive-waste site.

Wester believes that the cornerstone of Santa Fe's majestic backdrop is also the source of its radiation—the Sangre de Cristo Mountains.

"They got a lot of granite, which is associated with uranium," he explains. Though the mountains certainly affect radon levels, the probability of high radon levels in a home is hit-or-miss. "You can have many different radon levels in different homes in one neighborhood," Wester says.

On Aug. 3, the International Monetary Fund released an assessment of the US housing market forecasting growth through 2017. As more and more Santa Feans buy and sell their homes, many may be running into radon issues.

Though New Mexico currently doesn't require radon testing in homes before purchase, State Radon Officer Michael Taylor says the state's goal is to inform residents of the risk of radon gas. Real estate brokers are required to warn homebuyers of the threat.

"I tell clients to try and get as informed as possible…The best source is the EPA website," Philip Vander Wolk of Santa Fe Properties tells SFR. "There are areas that are more prone than others—areas where you have river beds, arroyos and acequias. The east side is prone to higher levels, and out in Eldorado."

Nine other states do have laws in place requiring the testing or discussion of potentially high radon levels with homebuyers. Eight of those states are in areas the EPA considers high-risk; the ninth, Alabama, is lower-risk with the exception of a few counties.

Once a broker has informed a homebuyer of radon risks, the buyer has the option of testing and, if higher levels are found, taking measures to mitigate exposure. "About 50 percent of my clients choose to do a radon test," Vander Wolk says.

Mitigation is relatively simple. The idea is to prevent radon gas from entering the home, either by creating a higher-pressure "bubble" under the house or coating the entire sub-structure in thick plastic.

Though Straub hasn't yet tested his home for radon levels, he says it's "certainly very high on my list of things to get done."