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Rocky Flats radiation facts need context William K. Terry April 7, 2019 Leroy Moore, in his letter "Low dose can be more dangerous" regarding Rocky Flats (Daily Camera, April 1), makes some claims that need context. He says that one alpha particle can cause a mutation that leads to cancer. Yes, that's true. But that's not the same as saying that you are at significant risk of cancer if one atom of an alpha emitter, such as plutonium-239, is lodged in your lung. First, since Pu-239 has a half-life of 24,000 years, there's only a 50-50 chance that it will emit that alpha-particle in the next 24,000 years. Furthermore, the vast majority of alpha particles absorbed in tissue don't cause cancer. To make this obvious, consider the radon in your lungs right now. The Front Range is a region of high airborne radon concentration. One can calculate that in two liters of air in your lungs in Boulder there are about 164,500 radon atoms, which emit an alpha particle every 2.9 seconds with energy slightly greater (more harmful) than that from Pu-239, and the daughter nucleus from the radon decay promptly emits another alpha particle of even greater energy. Since the half-life of radon222 is only 3. 8 days, that radon is equivalent to a lot more plutonium: specifically, 760 billion atoms of it. Radon can cause lung cancer, but in most people, even here, it doesn't. If Moore is concerned about alpha particles bombarding his lungs, he should move to a low-radon location. Moore cites research suggesting that low-level radiation can be more dangerous than highlevel radiation, because high doses kill cells, whereas low doses only mutate them. I don't have space to address this claim, but there is another body of research suggesting a "hormesis" effect: low radiation doses are actually beneficial. Healthy cells normally repair non-lethal radiation damage, a phenomenon essential to radiation therapy for cancer. William K. Terry Longmont, Colorado, USA
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