Dear Science,

I've just watched a YouTube video on how radiation from Fukushima was found all over the West Coast of the United States. It's been a while since I've seen much news on the reactor disaster, and I do believe it is time to start worrying about the impact of Fukushima particles. What have scientists figured out about the radiation leaking from the damaged reactors? Who should be worried at this point?

Radiation Alert

Science's opinion of the situation has changed little since March: If you aren't living in Japan—or planning travel to the region directly adjacent to the reactor—you have nothing to worry about from the radiation that leaked from the Fukushima reactors damaged during the massive earthquake and tsunami this winter.

Let's pick a particularly well-done study by Dr. Priyadarshi and colleagues at UCSD. These scientists are experts at detecting a rare radioactive isotope of sulfur, S-35. Usually, this isotope is created when cosmic rays slam into the atmosphere, causing gas molecules in the air to split and form a teeny-tiny amount of this rare atom. By detecting these minuscule amounts, they can indirectly study the cosmic rays. During the days and weeks following the Fukushima disaster—when workers were furiously pumping raw seawater into the reactor to cool the melting-down cores—these scientists began to detect higher amounts of S-35 in the atmosphere around their lab. They figured this radioactive sulfur was probably a byproduct of the seawater leaking out of the reactor, created when high-energy neutrons from the reactor bombarded chlorine ions in the seawater (from the sodium chloride, or salt), turning them into the radioactive sulfur-35 they know so well.

So, yes, these scientists—like quite a few others—detected radioactive elements almost certainly from Fukushima all the way in La Jolla. Isn't that dangerous? Not really. These scientists, and their detectors, are really good and sensitive at detecting even absurdly tiny numbers of radioactive atoms. The levels detected were too low to have any effect on living things. All of the radiation detected from Fukushima in the West Coast of the United States was like this: too paltry to have any effect. Really, truly, you have nothing to worry about from this amount of radiation. You should be far more concerned about the more run-of-the-mill air pollution—dust, soot and heavy metal particles—that blows across the Pacific from northeast Asia; those are in quantities high enough to affect human health. In some weeks, half of the air pollution in Seattle was blown across the ocean from Asia—enough pollution to cause asthma attacks, pneumonias, and all sorts of problems.

Calmly yours,


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