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A “Hot” Day at the Beach

A “Hot” Day at the Beach

ocean beach

Not long ago, on a beach near San Francisco, a citizen scientist took his Geiger counter in hand and went for a walk. Shrill beeps from the gadget indicated hot stuff on the sandy shore, at several times normal levels. He posted his “findings” on YouTube, and faster than a speeding beta particle, the video went viral. The commentary verdict was swift and sure: Fukushima.

It’s been three years since the March 2011 catastrophic triple whammy in Japan—the earthquake, tsunami, and subsequent meltdown at the Fukushima Dai-ichi nuclear plant. Airborne and surface radioactive elements, or radionuclides, blew to North America in nonhazardous concentrations in the months immediately after the disaster. Today, ocean scientists are watching and waiting for another shoe still expected to drop: the arrival on North American shores of radioactive ocean water from Japan.

All that beeping on the YouTube video, attributed wrongly to Fukushima, is actually from natural sources of radioactivity, mainly radioactive potassium and uranium found in sediments eroded from granite. Any Fukushima-derived radioactivity on a California beaches is readily drowned out by these much-stronger natural sources.

The radionuclide shoe scientists are actually listening for is cesium-134. Cousin to cesium-137, the main contaminant produced by Fukushima and similar nuclear power plant disasters, scarcer cesium-134 is a more useful tracer thanks to its specificity. Cesium-134 is produced only in nuclear power plants and has a short two-year half life, meaning that any detectable cesium-134 in our oceans can be fairly attributed to Fukushima.

So far, according to John Boesseler of Woods Hole Oceanographic institute, there is still no measurable cesium from Japanese waters at North American shores. Ocean waters take longer than you might think to travel the globe; complete ocean mixing takes roughly a thousand years. Based on various simulation models, many of which disagree, Boesseler and others expect that Fukushima radionuclides could arrive over the next two or three years.

If and when Fukushima radionuclides do arrive in North America, don’t expect much hoopla or more viral videos. They will be but a blip on the actual and figurative screen, not detectable by commercial grade Geiger counters, and also not a likely health threat.

Radioactivity from Fukushima is still a real source of concern in Japan, but at far-flung locales the nucleotides serve mainly to provide clues to understanding flow and mixing in the world’s oceans. Scientists are looking to cesium to help settle an ongoing battle between competing models of ocean dynamics, important to our overall understanding of global climate change.

Beach-loving citizen scientists, there is still an important role for you to play: Volunteers are needed to help monitor radiation levels worldwide. Visit for more information, or to check the current measurement results.  No Geiger counter required.