Three Fukushima Radiation Studies Reflect Extensive Monitoring Efforts

Three news items released Tuesday regarding the public health effects of radiation in the atmosphere as a result of the March 2011 Fukushima nuclear incident do little to lessen confusion surrounding the issue, but all point to intense radiation monitoring efforts happening on both sides of the Pacific Ocean.

A meeting of the American Geophysical Union's Ocean Science section revealed Tuesday that low levels of radioactive cesium could reach the shores of the North American West Coast by April of this year, according to a report by the San Francisco Chronicle.

The Chronicle reported that a collective of scientists and concerned citizens will begin collecting sea water in 20 gallon buckets from 16 sites along the Washington and California coasts and shipping them for testing at the Woods Hole Oceanographic Institution in Massachusetts.

Radioactive cesium-134, which has a halflife of two and a half years, would show up in tests, as would cesium-137. However, cesium-137 has a 30-year halflife, so the Wood's Hole tests cannot directly tie its presence to the Fukushima incident, the Chronicle reported.

The cesium plume, however, is expected to be so diluted it will be harmless.

Meanwhile, a study released Tuesday in the the Proceedings of the National Academy of Sciences suggested the mean doses of radiation exposure for Fukushima prefecture residents are comparable with background doses across Japan.

"Residents of communities bordering restricted areas around the Fukushima Dai-ichi Nuclear Power Plant received a radiation dose of 0.89-2.51 millisieverts per year (mSv/yr) in 2012, a dose similar to the 2 mSv/yr that residents of Japan can expect from natural sources," the study authors said in a statement.

The study, which involved 458 participants wearing dosimeters, as well as accounting for radiation exposure through inhalation and food consumption, used a linear no-threshold model, which assumes a health risk that's directly proportional to radiation exposure and that even the smallest amount of exposure carries some risk.

Although this study suggests Fukushima residents are at no more risk of exposure to radiation than they would be if the nuclear disaster did not occur, residents in Fukushima are still faced with myriad radiation concerns.

Tuesday Japan's Asahi Shimbun newspaper reported on very high levels of cesium in the soil of hundreds of reservoirs used to irrigate farmland around Fukushima prefecture, which is a rural and highly agricultural region of Japan.

"A joint survey by the prefectural government and a branch office of the farm ministry found that the levels exceed 8,000 becquerels per kilogram of soil in 576 reservoirs. In 14 of those cases, the level tops 100,000 becquerels," Asahi reported.

Many of these reservoirs, including the one that tested for "radioactive cesium of mind-boggling 370,000 becquerels per kilogram of soil." However, the water in this reservoir, which is in the Takagi district of Motomiya, some 55 kilometers west of the Fukushima campus, does not have detectible levels of cesium, Asahi reported.

Still, local rice farmers, like Tokuo Nemoto, 65, are concerned.

"Our family has been using the reservoir since the days of my grandfather. If it becomes impossible to use it, I will not be able to cultivate rice," he said.