Scientists keeping tabs on the eastward voyage of radioactive byproducts from the 2011 Fukushima Daiichi nuclear-power-station disaster in Japan suggest that radioactivity from the byproducts should peak off the US and Canadian coasts by the end of next year. After that, they are expected to begin a gradual decline to background levels.

The chief concern: Radioactivity from cesium-137, the longest-lived of two forms of cesium released in the disaster, which ocean surface currents have carried east. At its peak, levels of radioactivity from cesium-137 will still fall far below levels that the US and Canadian governments deem unsafe for drinking water, according to data in a study published Monday in the Proceedings of the National Academy of Sciences (PNAS).

via Fukushima radiation: US West Coast will likely see peak by end of 2015 –