Videos on Weibo and Douyin and articles on Baidu Baijiahao recently claimed the level of marine radioactive pollution is much worse near Japan and Europe compared to China, Russia, Australia, and the African continent.
The viral content included a series of maps purportedly showing data from the International Atomic Energy Agency, demonstrating “astonishing” radioactive pollution levels in the oceans surrounding Japan and Europe.
However, these claims are false. Although the images are indeed from a database maintained by the IAEA, its Marine Radioactivity Information System is not a real-time monitoring system.
The density and colors of the dots on the maps simply indicate the number of data samples and historical maximum radioactive readings collected by the system for the last six decades.
It is impossible to discern the current marine radioactive pollution levels from these maps.
What is MARIS?
The IAEA’s open-access database has been aggregating marine radioactivity measurements recorded by scientists since 1957. These data often come from published academic studies or technical reports, and the samples include seawater, sediments, and marine life.
The latest dataset was collected on Jan. 23, 2021, more than two years before Japan started discharging treated nuclear wastewater containing tritium from the Fukushima Daiichi Nuclear Power Plant on Aug. 24 this year.
What is shown on the maps?
MARIS offers two different interactive maps, namely the “Explore” and the “Explore (Beta),” through which users can “search and retrieve results of measurements of radionuclides” collected from the marine environment.
A self-media article on Baidu used images from the Explore page and falsely claimed that the maps show densely polluted waters in Europe and North America.
However, no radioactivity level information can be shown on this map.
Each dot on the “Explore” page represents a group of data collected at a particular location. Clicking on a data point generates a popup displaying summary information such as the latitude and longitude, sampling years, type of nuclides examined, the number of datasets, and so forth.
The density of data points simply illustrates the frequency of sample collections at each location over the years.
Another blog article on Baidu claimed that the Fukushima sea waters were among the most polluted because the map shows intense maroon-colored dots in that area.
Annie Lab found that this image was generated with the “samples” analysis option, which displays different colors corresponding to the sample counts of all nuclides available in the database. The darker color indicates that there were more samples; it does not show radioactivity intensity.
One Weibo video claimed that the Fukushima coastline recorded a high concentration of tritium even before the treated wastewater discharge began, using a map that was generated with MARIS’s “Explore (Beta)” set to display maximum tritium measurements.
While the video correctly stated that the tritium radioactivity levels in the seawater near the Fukushima Daiichi Nuclear Power Station were once very high — at 130,000 becquerels per cubic meter — this is because the map shows a historical record documented in January 2012, less than a year after the devastating nuclear accident took place following a massive earthquake and tsunami.
According to a 2020 report by the United Nations Scientific Committee on the Effects of Atomic Radiation, besides the initial explosion in 2011, contaminated groundwater, leakage, and other factors could have also contributed to the radioactive materials found near Fukushima at that time.
Annie Lab looked into the latest samples collected in January 2021 at the same location and found that the reading does not exceed 1,700 becquerels per cubic meter, which is equivalent to 1.7 becquerels per liter, a significantly lower level than the tritium concentration cap of 1,500 becquerels per liter set by the Japanese government.
Levels of tritium during discharge
Tokyo Electric Power Company (TEPCO), the operator of the nuclear power plant, finished the first round of wastewater discharge on Sept. 11.
Japan’s national broadcaster NHK reported the highest concentration of tritium detected during the release was 10 becquerels per liter, significantly below the 1,500 becquerels per liter limit.
TEPCO has also provided marine radiation monitoring data close to Fukushima that included not only their own measurement but also the data from the Fukushima Prefecture, the Ministry of the Environment, and the Nuclear Regulation Authority in the country.
Annie Lab contacted both the IAEA and MARIS teams for further clarification. We will update this article when we hear from them.