Radiation from Japan nuclear disaster spreads off U.S. shores

By Courtney Sherwood
PORTLAND, Ore., Dec 3 (Reuters) - Radiation from Japan's
2011 nuclear disaster has spread off North American shores and
contamination is increasing at previously identified sites,
although levels are still too low to threaten human or ocean
life, scientists said on Thursday.
Tests of hundreds of samples of Pacific Ocean water
confirmed that Japan's Fukushima nuclear power plant continues
to leak radioactive isotopes more than four years after its
meltdown, said Ken Buesseler, marine radiochemist with the Woods
Hole Oceanographic Institution.
Trace amounts of cesium-134 have been detected within
several hundred miles (km) of the Oregon, Washington and
California coasts in recent months, as well as offshore from
Canada's Vancouver Island.
Another isotope, cesium-137, a radioactive legacy of nuclear
weapons tests conducted from the 1950s through the 1970s, was
found at low levels in nearly every seawater sample tested by
Woods Hole, a nonprofit research institution.
"Despite the fact that the levels of contamination off our
shores remain well below government-established safety limits
for human health or to marine life, the changing values
underscore the need to more closely monitor contamination levels
across the Pacific," Buesseler said in an email.
In March 2011, a massive earthquake triggered a tsunami that
struck the Fukushima nuclear plant, 130 miles (209 km) northeast
of Tokyo, causing triple nuclear meltdowns and forcing more than
160,000 residents to flee from nearby towns. It was the world's
worst nuclear disaster since Chernobyl in 1986.
Last year, Woods Hole reported detectable radiation from
about 100 miles (160 km) off the coast of northern California,
and in April radiation was found off Canada's shores.
The latest readings measured the highest radiation levels
outside Japanese waters to date some 1,600 miles (2,574 km) west
of San Francisco.
The figures also confirm that the spread of radiation to
North American waters is not isolated to a handful of locations,
but can be detected along a stretch of more than 1,000 miles
(1,600 km) offshore.

(Editibg by Curtis Skinner; Editing by Sandra Maler)