What happened on March 11, 2011?
Still have questions?
What was the highest level of radioactivity near the power plant?
The accident at the Fukushima Dai-ichi Nuclear Power plant in 2011 resulted in the permanent or temporary relocation of more than 100,000 people living near the plant. It also resulted in millions of gallons of water containing radioactive contamination to be released to the Pacific Ocean—the largest accidental release of radioactivity to the ocean, second only to nuclear weapons testing in the 1950s and 60s. But how do these numbers compare to other measures of radioactivity in the ocean?
How much radioactivity was in the ocean before Fukushima?
How much radioactive strontium is in the ocean from Fukushima?
Should we be concerned about radioactivity in seafood?
How much radioactivity has been detected near North America?
How much radioactive cesium is in the ocean near Japan?
How much radioactivity does the U.S. allow in drinking water?
Should we be concerned about radioactivity in seafood?
Radioactive strontium near Japan (highest levels detected)
2015
How much radioactive strontium is in the ocean from Fukushima?
2016
Radioactive cesium near Japan (highest levels detected)
Many radioactive contaminants were released from Fukushima in addition to cesium. Of these, strontium-90 is particularly worrisome, as it can replace calcium in the bones of fish (and humans who eat contaminated fish) and is not removed from the body as fast as cesium. The highest levels of strontium-90 measured in the ocean to date have been 40 times lower than cesium-137. However, levels of are not declining. This may be due to the fact that it exists in higher concentrations in the wastewater stored at the nuclear power plant and in the groundwater beneath the site, both potential sources of ongoing releases to the ocean. Sources: Pere Masque, Autonomous University of Barcelona and Edith Cowan University; and Nuria Casacuberta, ETH Zurich
What happened on March 11, 2011?
2011
How much radioactive strontium is in the ocean from Fukushima?
2012
2013
2014
The U.S. does not have rules for radioactivity in the ocean, but it does have limits for drinking water, which are set by the EPA. Health concerns arise if a person drinks water above this limit every day for one year. We don’t drink seawater, but levels below the drinking water standard present even less of a risk when a person comes into contact with it through activities such as swimming, boating, or surfing. Source: Environmental Protection Agency (EPA)
How much radioactivity does the U.S. allow in drinking water?
NOTE: We report the amount of cesium-137 (and all radioactive isotopes) in units of Becquerels per cubic meter of seawater (Bq/m3), where one Bq is equal to one decay event per second and one m3 is a little over 264 gallons.
U.S. limit for radioactive cesium in drinking water 7,400 Bq/m3
How much radioactivity does the U.S. allow in drinking water?
Radioactive cesium in the Pacific before Fukushima 2 Bq/m3
Radioactive cesium in the Pacific after Fukushima (highest detected during WHOI-led cruises) 4,500 Bq/m3
What was the  highest level of radioactivity near the power plant?
50,000,000 Bq/m3
At its peak, radioactive cesium in the water near the Fukushima Dai-ichi nuclear power plant was reported by the Japanese to be 50 million times higher than levels before the accident. These levels were high enough to pose a direct threat to marine life and the releases continued for a short period in April 2011 until workers were able to stop the largest leaks. Thankfully concentrations of this magnitude were not detected in any of the samples collected during research cruises off shore. Source: Tokyo Electric Power Company (TEPCO)
Maximum radioactive cesium:
What was the highest level of radioactivity near the power plant?
1960
To exceed Japanese limits
Level of radioactive cesium in sea water necessary to exceed U.S. limits for radiation in seafood
Should we be concerned about radioactivity in seafood?
Radioactive cesium in the Pacific  before Fukushima 2 Bq/m3
Each country sets limits for the amount of radioactive cesium allowed in fish and other seafood. After the accident at Fukushima, the Japanese government lowered its limit, making it one of the strictest in the world. If seawater contained the amounts of radioactive cesium shown here, fish living in it would exceed the limits for radioactivity in seafood sold in Japan (100 Bq/kg) and the U.S. (1,200 Bq/kg). So far, no fish have been caught in U.S. waters or imported to the U.S. that exceeded either of these limits. Source: FDA
Should we be concerned about radioactivity in seafood?
How much radioactivity was in the ocean before Fukushima?
How much radioactive strontium is in the ocean from Fukushima?
What was the highest amount of radioactivity near the power plant?
How much radioactivity has been detected near North America?
How much radioactive cesium is in the ocean near Japan?
How much radioactivity does the U.S. allow in drinking water?
Fukushima and Radiation in the Ocean: How much?
4500 Bq/m3
Radioactive cesium-137 was the most abundant long-term radioactive contaminant released into the ocean from Fukushima. Concentrations off shore near Japan (between 1/2 and 60 miles) were highest in 2011, but at levels that would result in less exposure over the course of one year than a single dental X-ray. Data from later WHOI-led research cruises found that radioactive cesium is declining, but not towards pre-accident levels—a clear sign that releases of contaminants continue. Whether this is from the reactors, storage tanks, or groundwater is not clear. Source: Data from WHOI-led cruises, 2011-2015
77 Bq/m3
How much radioactive cesium is in the ocean near Japan?
52 Bq/m3
131 Bq/m3
65 Bq/m3
64 Bq/m3
Amount of radioactive cesium off shore near Japan (highest levels detected during WHOI-led cruises)
201 Bq/m3
How much radioactive cesium is in the ocean near Japan?
Radioactive cesium in the Pacific after Fukushima (highest levels detected)
50 Bq/m3
The ocean contains many radioactive elements, some natural and some the result of human activity. Before March 2011, there was a small amount of radioactive cesium-137 (the most abundant source of human-caused contamination) in the Pacific from nuclear weapons testing in the 1950s and 60s that was steadily declining due to radioactive decay. Source: International Atomic Energy Agency (IAEA)
How much radioactivity was in the ocean before Fukushima?
2 Bq/m3
How much radioactivity was in the ocean before Fukushima?
Radioactive cesium in the Pacific before Fukushima
Radioactivity detected near North America (highest levels detected)
Source: ourradioactiveocean.org
11 Bq/m3
How much radioactivity has been detected near North America?
6 Bq/m3
Ocean currents carry contaminants from Fukushima across the Pacific Ocean in about 3-4 years. WHOI researchers detected the first signs of radioactive cesium near Uclulet, British Columbia, in February 2015 and found the highest levels about 1,500 miles north of Hawaii in the summer of 2015. However, both are much lower than levels near Japan and only slightly elevated over what was already in the Pacific prior to Fukushima (2 Bq/m3).
How much radioactivity has been detected near North America?