Getting some rays

Radiation is cumulative

Although our exposure to the first type of radiation, the ionizing, is minimal, it accumulates in our bodies over our lifetimes, and it is permanent. If the level gets too high, we can be harmed at the molecular, cellular or genetic level. Cells can be allowed to grow abnormally, causing cancer, most commonly of the skin, thyroid, stomach, lung, breast and multiple myeloma. Radiation can mutate genes, something that can give children born after exposure slower growth and a smaller-than-normal head or brain.

High doses, as from aggressive radiation treatment or fallout from a nuclear bomb, can cause radiation sickness. Symptoms can range from weakness, hair loss, nausea and vomiting, skin burns and reduced organ function. The most severe cases cause fatalities within two months of exposure; more than 140,000 deaths were reported within four months of the bombing of Hiroshima.

What more commonly affects medical consumers — especially children, whose cells are dividing more rapidly — are the radiation risks from exposure to diagnostic tests. Before x-ray machines were invented, exploratory surgery was the only way to diagnose many ills. We’re lucky we can find out what’s wrong with us much less invasively. Many disorders of the skeletal, digestive, urinary, cardiovascular or other systems can be found with a quick x-ray or CT scan.

Although the level of radiation these machines emit is strictly regulated by the Food and Drug Administration, repeated exposure increases risk. And risk is on an upswing. About 30 years ago we got about 11 percent of our radiation exposure from x-rays; now it’s about 35 percent, according to the National Council on Radiation Protection and Measurements.

A standard chest x-ray gives us the same amount of exposure we would get in daily life from natural environmental sources over a 10-day stretch of time, says the American College of Radiology and the Radiological Society of North America. So it may not be as much as we perceive. To put it in specific numbers, the ACR and RSNA have explained that with radiation measured in the millisievert, or mSv, we typically get about three mSv per year from other sources. That chest x-ray has 0.1 mSv. When Junior needs his calf x-rayed after his tumble in the softball game, he gets only 0.001 mSv. That mammogram you keep putting off? Only 0.7 mSv. Upper GI radiography gives you two mSv, and the lower GI four mSv.

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