The Emergency Situations Ministry's press service said three expeditions between 2003 and 2005 in the north of the Sea of Japan and the Okhotsk Sea had revealed the content of toxic substances had increased, but remained within safe levels.
"The expedition starts July 15," the ministry said. "The scientific and research vessel Pavel Gordiyenko will set off from the port of Vladivostok to the presumed sites of disposed hazardous substances."
The ministry said the expedition would use an underwater apparatus and sonar equipment to detect sites. Scientists will also take samples of seawater and sediments.
"The Emergency Situations Ministry expedition to the Sea of Japan and the Okhotsk Sea will last until August 26," the ministry said. "The obtained data will help to assess not only the current condition of these disposal sites but also the level of danger they present to the environment."