Radiation from the 2011 Fukushima Dai-ichi nuclear power plant disaster has reached the United States, but will likely peak by the end of next year.
Research published Monday in the Proceedings of the National Academy of Sciences concluded that even at its highest level, concentrations of cesium-137 from Fukushima will be far lower than levels considered safe for drinking water in the United States and Canada.
Both cesium isotopes were already present in the Pacific Ocean because of nuclear weapon testing in the 1950s and 1960s, but the 134 isotope has a much shorter half-life.
Previous research has reached similar conclusions, but Monday’s publication includes the latest data, gathered in February 2014.
It found that radiation started to reach the continental shelf off of Canada last year and has increased since then.
It confirmed previous findings that radiation levels in the Pacific are 500 to 1,000 times smaller than that from dental X-rays.
Following the peak late next year of radiation, concentrations will start to fall, the authors said.