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Fears of fallout: Radiation concerns rise, but mostly unfounded

The recent news emanating from Japan about radioactive fallout drifting from a stricken nuclear power complex is a reminder that radiation can pose a health risk.

Last week, for instance, the Food and Drug Administration banned imports of milk, fresh fruit and vegetables from the area of Japan exposed to fallout in the aftermath of the catastrophic earthquake and tsunami.

Worries about possible exposure to fallout, in fact, drifted thousands of miles to North Dakota, where some called state health officials to ask whether they should take potassium iodide tablets as a precaution against contamination.

Quick answer: No. The amounts of radioactivity that reached the United States are minuscule and pose no health risk, officials say.

But radiation is all around us in very small doses. It bombards our bodies through cosmic rays; it's emitted from minerals in the soil; it's even present in some of the foods we eat - in infinitesimal amounts.

The natural radiation we're exposed to in our everyday lives is called background radiation.

Worldwide, the average dose of radiation from natural sources is 2.4 to 2.8 millisieverts, a measuring unit of very small levels of radioactivity.

Roughly half of that amount comes from inhalation, mainly radon gas, a product of decaying uranium contained in rocks and soils.

Background radiation is a bit higher around Fargo-Moorhead, at about 3 millisieverts, according to Brent Colby, a radiology physicist for Sanford Health in Fargo.

That's likely because radon levels across all of North Dakota and much of western Minnesota are higher than many areas, according to the Environmental Protection Agency.

So radon that could be seeping into basements, through cracks in the foundation, drain tiles or sump-pump wells, should be of greater concern to most homeowners than the minuscule levels of radiation that drift thousands of miles from Japan, says Terry O'Clair, who heads the air quality division of the North Dakota Department of Health.

"We have not seen any higher levels in North Dakota," O'Clair said of airborne radiation since disaster struck the Japan reactors March 11. "We don't expect any."

As of early last week, the EPA said radiation readings from its surveillance network on the West Coast were "hundreds of thousands to millions of times below levels of concern."

Radon, on the other hand, seldom makes big headlines. For years, public health officials have recommended that people in the area test for radon gas levels in their basements.

Test kits are available from many hardware stores or health outlets. If radon levels are of concern, ventilation can solve the problem. The North Dakota Department of Health's website provides more information, including a list of contractors to address radon levels.

Cosmic rays and terrestrial gamma rays contribute the next largest share, followed by tiny amounts of radiation we ingest, such as the potassium-40 in a banana.

Air travel exposes people to higher levels of cosmic radiation. The dose from a flight from Vancouver to Honolulu would yield a dose equal roughly to a thousandth of a chest X-ray.

In fact, modern medicine can deliver doses of radiation much higher than the natural background levels.

To compare the relative levels of radiation exposure for diagnostic images, medical professionals consider a chest X-ray typical.

Dental X-rays deliver about half as much radiation as a chest X-ray, while an abdominal CT scan is the equivalent of 35 chest X-rays. A cardiac angiograph, used to detect blockages in coronary arteries, can deliver the equivalent of a whopping 211 chest X-rays.

An important caveat: Radiation dosages differ widely, depending upon equipment, techniques and how much exposure is considered necessary to provide an image able to make a diagnosis.

A study found that abdominal CT scans, for instance, can vary as much as 13-fold in the effective radiation dose, depending on the equipment and technique used.

Medical professionals, well aware of the tradeoffs between benefits and risks involving diagnostic or therapeutic use of radiation, try to strike the right balance, Colby says.

"What is the safe dose?" he asks. "That is the question everybody wants answered. We haggle about that."

Where does that leave the patient who wants to know that the dosage is not higher than needed?

"As a patient," Colby says, "it's tough to know."

Still, patients should ask their doctors about the level of exposure they will receive from a diagnostic test or a treatment.

"I know what my physicians want to see here so I deliver exactly that," Colby says. "We set them at the lowest dose that the physician will tolerate with confidence."

But for most people most of the time, very low levels of radiation literally are part of the background. Even the effects of a catastrophic accidental release are very diluted for most who are far downwind.

The world's worst nuclear accident, the explosion of a reactor in Chernobyl, Ukraine, 25 years ago, was far worse than the disaster unfolding so far in Japan.

The average worldwide annual effective dose from the Chernobyl accident, according to a scientific panel of the United Nations, is 1,200 times smaller than the 2.4 millisieverts considered the global background radiation level.

Radiation understandably causes very big health fears, but usually comes in very small doses.
