7 Apr (NucNet): Scientists have for the first time detected the presence of small amounts of radioactivity from the 2011 Fukushima-Daiichi accident in a seawater sample from the shoreline of Canada, but said levels are “well below” internationally established levels of concern to humans and marine life.
Scientists from the Massachusetts-based Woods Hole Oceanographic Institution (WHOI) said the sample, which was collected on 19 February 2015 in Ucluelet, west of Vancouver in British Columbia, contained trace amounts of caesium-134 (Cs-134) and caesium-137 (Cs-137).
In a statement WHOI said if someone were to swim for six hours a day every day of the year in water that contained levels of caesium twice as high as the Ucluelet sample, the radiation dose they would receive would still be more than one thousand times less than that of a single dental X-ray.
“Radioactivity can be dangerous, and we should be carefully monitoring the oceans after what is certainly the largest accidental release of radioactive contaminants to the oceans in history,” said Ken Buesseler, a marine chemist at WHOI who has been measuring levels of radioactivity in seawater samples from across the Pacific since 2011. “However, the levels we detected in Ucluelet are extremely low.”
WHOI said the caesium measured in Ucluelet is far below where one might expect any measurable risk to human health or marine life, according to international health agencies. And it is more than 1,000 times lower than acceptable limits in drinking water set by the US Environmental Protection Agency.
The WHOI scientists, with the help of volunteers, have collected samples at more than 60 sites along the US and Canadian west coast and Hawaii over the past 15 months for traces of radioactive isotopes from Fukushima-Daiichi. In November 2014, the team reported their first sample containing detectable radioactivity from Fukushima-Daiichi about 150 km offshore from northern California. However, no radiation has yet been found along any of the beaches or shorelines where sampling has been taking place since 2013.
The Ucluelet sample contained 1.4 becquerels per cubic metre (Bq/m3) of caesium-134 and 5.8 Bq/m3 of caesium-137. These levels are comparable to those measured off the coast of northern California last summer.
Mr Buesseler said he has had to rely on a crowd-funding and citizen-science initiative known as “Our Radioactive Ocean” to collect samples because no US federal agency is responsible for monitoring radiation in coastal waters.
The results are available on the website www.ourradioactiveocean.org.