This is not the case with another isotope, iodine-129, released concurrently with iodine-131.

Its high radioactivity, however, makes it very detectable by the gamma-ray spectroscopy instruments used by the Dartmouth team in its analyses. 'It releases a lot of radioactivity, which makes it dangerous, but it's gone very quickly so there is no long term exposure risk,' he says. It does have a relatively short half-life, which is both a blessing and a curse, Landis notes. The radioisotope iodine-131, a significant constituent of the fallout, is a by-product of nuclear fission, highly radioactive, acutely toxic and presents a health risk upon its release to the environment. But even in these concentrations, stream and river transport are expected to result in significant dilution. However, sampling of Mink Brook stream sediments showed a doubling of iodine concentrations relative to what was found in soils. Landis comments that 'at these levels, it is unlikely that this is going to cause measurable health consequences.' The paper reports that testing in New Hampshire's Mink Brook watershed during March through May 2011 showed the amount of radioactive iodine deposition in the soil was minimal, with calculations revealing the total amount to be on the order of 6,000 atoms per square meter. 'We took up this study mostly as concerned scientists in our own right, wondering how much of this contaminant is really coming down, and where the iodine is moving in the landscape.' 'Though regrettable, the Japanese catastrophe did provide a unique opportunity to examine the transport and accumulation of radioactive iodine in the environment,' Landis says. Landis and a team drawn from Dartmouth's Department of Earth Science and Department of Geography recently published a paper in the Proceedings of the National Academy of Sciences addressing such concerns.

Japan reactor meltdown 2012