A decade ago, the accident at the Fukushima Daiichi nuclear power plant released radioactive material into the air and sea. According to Japan, the marine radioactivity levels have been steadily dropping since the accident. To ensure transparency, international scientists were invited to come and check in person.
These inter-laboratory comparisons are a service offered by the International Atomic Energy Agency to its member states, to double-check the reliability of their methods for monitoring the environment.

Data cited taken from the ?with permission by TEPCO