Elevated levels of cesium found in fish off Japan’s east coast 18 months after the Fukushima Dai-ichi nuclear disaster suggest a “continuing source” of radiation in the ocean, a new study revealed on Thursday.
Marine chemist Ken Buesseler of the Woods Hole Oceanographic Institution reviewed official Japanese data on radiation levels in fish, shellfish and seaweed collected near the crippled nuclear plant.
Buesseler concluded the lingering contamination may be due to low-level leaks from the facility or contaminated sediment on the ocean floor, according to his research, published on Thursday in the US magazine Science.
He estimated that about 40 percent of fish caught near Fukushima are considered unfit for consumption under Japanese regulations.
“To predict how the patterns of contamination will change over time will take more than just studies of fish,” said Buesseler, who led an international research cruise last year to study the spread of radionuclides from Fukushima.
“What we really need is a better understanding of the sources and sinks of cesium and other radionuclides that continue to drive what we’re seeing in the ocean off Fukushima,” he said.
A tsunami, sparked by a massive undersea earthquake, swamped the Fukushima Dai-ichi nuclear power plant in March last year.
Reactors went into meltdown, spewing radiation over a large swathe of Japan’s agriculture-heavy northeast, in the planet’s worst atomic disaster in a generation. About 19,000 people were killed or remain missing.
Cesium levels vary across fish types, though Buesseler also found that demersal, or bottom-dwelling fish, consistently showed the highest cesium counts from the damaged nuclear plant.