In 1984, radiation was detected on a worker at a nuclear power plant in Pennsylvania. When the radioactive particles were tested, they were found not to have originated within the plant. They had arrived with the worker from somewhere else. The source of the radioactivity was eventually found to be radon, a naturally occurring gas present in the worker’s home.
The presence (and the dangers) of radon in the residences of millions of Americans became clear to science and medicine only 30 years ago. According to the Environmental Protection Agency’s (EPA) 2003 Assessment of Risks from Radon in Homes report, radon, which is the number two cause of lung cancer after cigarette smoke, is responsible for an estimated 21,000 deaths in the U.S. annually, thousands more than are killed by drunk driving each year.
In order to monitor and mitigate health risks associated with radon, the Oregon Health Authority (OHA) compiles records of every radon test conducted in the state. Since the 1990s, this data has been used by Emeritus Professor Dr. Scott Burns, Department of Geology, and his students to assemble and publish an assessment of radon levels in all of Oregon’s zip codes. The most recent 2013 report and accompanying maps are available online and they show the Portland metro region to be a hotspot for radon gas.
A map created by Dr. Burns and his research team identifies nine zip codes in the metro region, many in North and Northeast Portland, with levels of radon gas at 4+ picocuries (a measurement of intensity of radioactivity) per liter, a level of high risk to public health according to the EPA. 28 other zip codes in the cities of Portland, Beaverton, Hillsboro, Gresham, Wood Village, Lake Oswego, Wilsonville, and others range between two and four picocuries/liter, placing residents at moderate health risks from exposure to radon. These results were obtained from the analysis of long-term radon tests. The EPA recommends residents protect themselves by having their dwellings tested and taking steps to counteract the accumulation of the radioactive gas indoors. And according to the EPA, the best time to test for radon is during the winter.
Selicity Icefire, a post-bac student earning a Bachelor of Science in Geology with a focus on engineering geology, working with Dr. Burns, noted the research team had found little data specifically related to seasonality while compiling the 2013 report. She knew testing for radon was a good idea, but she wondered, was winter really the best time of year to screen for radon in homes? It turned out the EPA provided her with little information to back up their claim due to only long-term radon test data analyses being available. So with her curiosity not quelled, Icefire decided to find out for herself.
“The EPA recommends testing in winter for the best results,” Icefire said. “But they don’t really specify when during winter or if winter is from the end of December to the end of March, or if it includes fall and spring months as well. So I saw a void in the data and decided to ask Dr. Burns if I could take on the project and answer some of those questions about testing and seasonality since the 2013 study was the first to have a large data set of short-term radon readings.”
Icefire began by defining seasonal boundaries by weather patterns and changes in the Northwest’s climate. Winter, she reasoned, was characterized by the cool, rainy season from October to March. Summer lasted from June through August. The remaining months she categorized as variable “swing” months—times of the year when temperatures are neither warm nor cold and weather patterns are less predictable. Reason suggests the EPA’s claim might be true. During winter, residents close their windows and seal their homes to retain heat and save energy and money. In hermetically sealed homes, radon has no way to escape. During the summer months, people often open up their residences allowing radon to escape into the atmosphere.
Icefire enlisted the help of friends and neighbors, asking them to have their houses tested for radon. From the statewide data, she looked at 14,873 records of short-term tests (tests that screen for radon for between three and seven days). Analyzing the data, she noticed a pattern emerging.
“When I looked at the data, my findings showed that there was a significant difference between testing for radon in summer versus testing in winter,” Icefire said. “During winter, radon levels averaged 4.8 picocuries per liter. That’s well above the EPA recommended level for action.”
Radon is the byproduct of Uranium 238, an elemental stop along the decay chain that transforms uranium into stable lead. According to Icefire, concentrations of radon arrived in the metro region and the broader Northwest 15 to 15 thousand years ago when the Missoula floods brought massive amounts of granite to the area from the Idaho Batholith.
“With all the history of volcanic activity in the region, most people think we’re sitting on top of nothing but basalt,” Icefire said. “But there are massive deposits of granitic materials below our feet full of uranium and thorium. After several half-lives, the uranium and thorium becomes radium gas that can make its way through the porous granite gravel and into our homes. It’s a gas for about four days. People inhale it. The radon goes through more decay events becoming solid again and then people are left with a radioactive particle in their lungs.”
This is the process, Icefire explained, that causes lung cancer for so many exposed to radon gas.
Icefire’s findings seem to confirm the EPA’s claim that winter is the best time to test a residence for accumulations of radon gas. Looking at the “Radon Hazard Potential in Oregon” map created by Dr. Burns and his team, this information should be of use to large portions of the state’s population. The map indicates that populated regions along the Columbia and Snake Rivers and much of the Grande Ronde and Willamette Valleys could potentially contain dangerous levels of radon gas. People living in locations like these can benefit themselves by testing for radon when they are most likely to get the best results, which, as Icefire’s study confirms is during the winter. These same tests also help the OHA better locate areas in the state where radon levels may be dangerously high.