Some of you may have noticed a video spreading on Facebook and Twitter lately in which a man took a Geiger counter to a beach in Pacifica and found levels of radiation that set off alarms on his counter as soon as he nears the water (see above). He attributes this to the radiation plume from the 2011 Fukushima disaster finally reaching our coast, however there have yet to be independent scientific confirmations of this. In short, you should be concerned, but skeptical.

The earthquake and tsunami of March 2011 caused a significant nuclear disaster for northeastern Japan, and radioactive water from the Fukushima Dai-ichi plant leached into the Pacific in unknown quantities. Debris from the tsunami began hitting our shores last year, and concerns have been raised about levels of radioactive cesium-137, with a half-life of 30 years, in Pacific ocean waters.

This study, commissioned from the Congressional Research Service last year, downplays the risks of radioactive contamination to marine life and ocean water, noting both a British scientist and scientists at the Woods Hole Oceanographic Institution in Massachusetts as saying that "levels in seafood should continue to be monitored, but ... radiation in the ocean very quickly becomes diluted and should not be a problem beyond the coast of Japan."

But, on the other hand, as a professor emeritus at Colorado State told the New York Times, "There can be hot spots far away from an accident, and places in between that are fine." Also, as the Congressional study admitted, "There remains the slight potential for a relatively narrow corridor of highly contaminated water leading away from Japan … [and] Regardless of slow ocean transport, the long half-life of radioactive cesium isotopes means that radioactive contaminants could remain a valid concern for years."

Meanwhile, Dr. Ken Buesseler of Woods Hole, speaking to the Cape Cod Times, cautions that no organized testing of Pacific ocean water or marine life has been happening, and it should be. The government has so far poo-pooed the need for such testing, perhaps because of that brief study commissioned by Congress, but, Buesseler says:

We don’t have a U.S. agency responsible for radiation in the ocean. It’s really bizarre... I’d very much like to see study on our side of the ocean just to confirm these values and build some confidence with the public that’s been concerned about this. They’re right to be concerned — as scientists we’re telling them they shouldn’t be, but it’d be nice to have a few more data points to fill that gap.

You should probably ignore all the anti-alarmist schtick that employs the radioactive-banana comparison, like this post on Forbes from last month. Bananas do contain radiation, in the form of potassium-40, however human bodies have evolved repair mechanisms to deal with this naturally occurring radiation, which also only affects the body for a few hours. Cesium-137 is a relatively much newer and more harmful substance.

And as for the video above, one spurious issue is the fact that he's testing for radiation in the air, and from sea spray, presumably, seeing levels of 132 to 152 clicks per minute. (See this explanation from ModernSurvivalBlog of how to interpret those numbers, and what risks, or lack thereof, they represent.) Most scientists seem to agree that our main concern is not going to be from air exposure, but from water exposure, in particular from ingesting contaminated seafood that leaves radioactive particles in our digestive tract for extended periods of time. Seafood testing has been ongoing, but you can likely expect more headlines in future months and years as cesium-137 makes appearances in different fish populations at different levels. The long-term health effects of eating such seafood remain totally unclear, and continue to be argued over.

Below, a nice animated gif showing where the radioactive particles are estimated to be in the Pacific, based on ocean currents, over the first couple of years post-Fukushima.