Radioactive iodine was found in kelp off the US West Coast following last year's earthquake-triggered Fukushima Daiichi nuclear meltdown, according to a new study.
A researcher at Case Western Reserve University has detected tiny amounts of Iodine 131 from Japan in rainwater collected from the roof of a campus building.
Radioactive contamination of the sea from Fukushima is likely to be only a local problem, but could lead to an exclusion zone if there is a major release of long-term pollutants, scientists say.
France's nuclear monitor said on Thursday that the amount of caesium 137 that leaked into the Pacific from the Fukushima disaster was the greatest single nuclear contamination of the sea ever seen.
Two workers from Japan's stricken Fukushima nuclear plant have been contaminated by high levels of radioactive iodine, the operator said Monday, prompting fears over their long-term health.
Elevated levels of the radioactive element iodine-131 that were detected in several nations have been identified as likely originating at a Hungarian research institute, nuclear authorities said Thursday.
France's nuclear watchdog on Tuesday said it had detected traces of radioactive iodine in the air last week after similarly low contamination was reported by the Czech Republic, Poland, Slovakia and Austria.
Environmental group Greenpeace warned Thursday that marine life it tested more than 20 kilometres (12 miles) off Japan's stricken Fukushima nuclear plant showed radiation far above legal limits.