Naturally occurring radioactivity part of Western Slope life
Coloradans are subjected to, on average, four times more naturally occurring radiation than the average American. It is the price of living in a mountainous and geologically rich region, but the full impact of that background radiation on residents’ health is poorly understood.
Aside from an increased risk of skin cancer because of higher elevations and a heightened but avoidable lung-cancer risk from radon seeping from uranium-rich soils, it appears the higher-than-average background radiation levels in Colorado, and Mesa County in particular, are still lower than what would be deemed hazardous.
Some experts even believe the low levels may have beneficial effects, up to a point, but it is notoriously difficult to fully isolate the effects of something as ubiquitous as background radiation from the hundreds of other factors that affect human health.
Whatever the impacts, it is clear people in this region live surrounded by heightened — and ancient — levels of radiation.
When Grand Junction’s Climax Uranium Mill closed its doors for the final time in 1970, it left a lingering legacy of radiation in the community. But it was not the first do so.
About 240 million years ago, as the large, shallow seas that covered what is now the Colorado Plateau gradually receded, uranium deposits slowly grew.
In the late 1950s, that uranium gave rise to the industry that resulted in the mill here and the numerous uranium mines that sprang up throughout western Colorado and Utah. Now, with proposals for a nuclear plant on the Green River and a mill in Montrose County, there has been speculation the industry may be making a comeback.
But the radiation emitted by its raw product — or the numerous other sources of so-called natural background radiation — never left.
“As beings on this planet, we are essentially born into radiation,” said Marty Jacobson, research director at St. Mary’s Hospital’s Saccomanno Research Institute, who has studied the effects of radiation on humans at the cellular level.
Four times the exposure
But as beings in Colorado, we are born into more than the average American. Scientists have estimated the average U.S. resident’s exposure to so-called natural background radiation is 300 millirems, the unit in which radiation is measured in the United States. The average Coloradan is exposed to 1,180 millirems.
That natural background radiation comes at us from two directions: cosmic radiation, which derives from the sun and is more intense here than in other regions of the country because of Colorado’s higher elevation, and terrestrial radiation seeping from the area’s soils, which are particularly rich in naturally occurring uranium. That uranium also decays into radon, a gas that can be trapped in the air.
About half of Americans’ background radiation exposure is thought to come from these natural sources, with the other half coming from man-made, mainly medical, sources.
Those man-made sources increased from 20 to 50 percent of Americans’ exposure over the past two decades as the use of procedures such as CT scans increased, according to a 2009 study by the National Council on Radiation Protection & Measurements.
Man-made radiation is thought to be generally consistent, on average, across U.S. regions, but natural radiation is not. And though man-made radiation exposure has changed, natural exposure has remained about the same for millions of years.
In Grand Junction, where an estimated 300,000 tons of sand-like uranium tailings were used in road and building construction from 1951 to 1970, radiation exposure is historically a fact of life. Numerous remediation efforts have removed most, though not all, of those tailings, but the area’s radioactive legacy is much older than those missteps, and it’s no secret.
“It’s been a concern for a long time from people both living in the area and moving into the area,” said Teresa Coons, an immunologist who moved to Grand Junction in 2000 to study the health effects of the uranium industry on uranium miners and mill workers.
“I’ll still get a call every once in a while from some out-of-town person thinking of moving here wanting to know whether everyone here is dying from cancer,” she said with a laugh.
Safe, but how safe?
At 4,500 feet above sea level, Mesa County receives about 44 millirems per year from outer space, according to EPA estimates, compared with the 26 millirems of sea-level areas.
All high-elevation areas face higher cosmic radiation levels, but what makes Colorado rather unique is that its elevation is combined with uranium-rich soils, particularly in the western part of the state.
The average American receives a dose of 28 millirems from terrestrial radiation, but Coloradans receive 46 millirem of the radiation seeping from its soils. Western Coloradans receive 90 millirems.
Combined with a higher amount of radon gas seeping out of the state’s uranium-rich soils, the average yearly dosage of natural background radiation for Coloradans is almost four times the national average.
There is broad scientific agreement, however, that even those Colorado doses are far below the thresholds at which health effects could be expected.
In fact, Coloradans have lower overall cancer rates than the national average, according to data collected by local and state cancer registries. This is likely because of the relatively healthier diet and lifestyle of the state’s residents, according to several experts interviewed.
They said this underlined the fact that so many other, often more important factors go into determining a person’s health, and residents of Mesa County and Colorado should not be overly concerned about the low doses of radiation around them, as long they take some precautions.
“While Colorado ranks among the lowest for overall cancer deaths, there are a few cancers with higher rates in Colorado,” said David Schauer, executive director of the National Council on Radiation Protection and Measurements.
Coloradans, for instance, are at greater risk of getting skin and lung cancer.
Prone to skin cancer
Skin cancer, including serious forms such as melanoma, is the greatest danger Coloradans face from natural radiation.
“Melanoma is a serious concern due to our elevation, the high number of sunny days and our generally outdoor lifestyles,” said Jack Finch, statistical analyst at the Colorado Central Cancer Registry.
Being higher means the atmosphere is thinner and offers less natural protection from harmful ultraviolet radiation. The Colorado Department of Public Health says the state’s incidence of melanoma is 30 percent higher than the rest of the country and rising.
Lung cancer historically has been high in Mesa County relative to other parts of the state, but that number has dropped in recent decades as former uranium miners died and smoking rates decreased. Mesa County remains above state averages today, according to the cancer registry’s data.
The vast majority of those cases are caused by smoking, but a small fraction of them — around 10 percent, or 15,000 to 20,000, of lung-cancer deaths each year, according to the National Cancer Institute — are caused by radon, the leading cause of lung cancer among nonsmokers and a contributing factor for smokers.
“In general, lung cancer rates follow smoking trends,” Finch said. “Radon is a very distant second.”
Too much radon
in half of homes
As uranium slowly decays under our feet, it disintegrates into other elements, including the colorless, tasteless, odorless gas radon. Radon then seeps into the air where it can get trapped in mines, houses or other structures. It is ubiquitous wherever a lot of uranium can be found in the soil, such as western Colorado.
The gas has a half-life of only a few days, but it decays into slightly heavier particles that can stick to dust or cigarette smoke, which can then be inhaled and have been shown to lead to increased risk of lung cancer.
“It isn’t the radon itself that is the problem, it’s the particles,” said Coons, who studied lung cancer incidence in uranium miners, who were trapped breathing radon-laden air underground.
“If you can keep the air moving, you don’t have to worry about it.
“There’s almost no comparison between smoking and radon for lung cancer, but I would go to battle with anyone who says those who don’t smoke aren’t affected,” she added.
It should be noted that incidence of lung cancer in Colorado is significantly lower than the national average, about 28 percent less in 2007, the most recent year for which data is available. Smoking rates are also lower in the state than the national average; in 2007, Coloradans smoked 5.6 percent less than the national average.
No data could be found on the percentage of those Colorado lung cancer cases linked directly or in part to radon.
Radon remains by far, however, the most prevalent source of natural radiation, making up more than half of Americans’ naturally occurring background radiation exposure. Colorado radon levels are about four times higher than the U.S. average, though most of the other Rocky Mountain states, as well as some Great Plains and Appalachian states, are in the same boat, according to EPA data.
About half of Colorado homes have radon levels above the level at which the EPA recommends taking action to reduce levels. Contractors and do-it-yourself kits are available to test homes for radon levels.
A more optimistic model
As long as precautions are taken to limit skin-cancer risk and monitor indoor radon, it is not at all difficult to avoid major health problems originating from background radiation in Mesa County and the state in general, experts agree, despite all of the statistics showing above-average radiation levels in the region.
Some scientists even adhere to the controversial idea that low levels of radiation, such as those that naturally surround us, can be good for human health. This is called the hormesis model.
St. Mary’s Jacobson is one of them.
“Hormesis says that certain things at low levels can actually be protective, including chemicals and radiation,” he said.
Just as a small dose of a virus may be used to immunize someone against the virus’ full onslaught, a small dose of radiation, the hormesis model posits, might limit the damage of further radiation or even disease.
The more mainstream theory is the linear, no threshold model, or LNT, which says no amount of radiation is beneficial, and the damage radiation causes is proportional to dose, no matter how small.
This more conservative model is the one adopted by government agencies when creating guidelines about the permitted amount of radiation to which a population should be exposed.
Coons also believes the hormesis model is accurate.
“There are people who would violently disagree with me, but that’s how science moves forward, I guess,” she said.
But Coons added that more research is needed before the model can be truly useful in helping us understand the risks of low-level radiation such as that found naturally in Colorado.
“The big question is: What is the threshold past which radiation is only harmful and no longer beneficial?” she said.