The increase in background radiation in Severodvinsk in the day of the explosion at a military facility near the village of Nyonoksa on 8 August occurred due to the passing cloud of radioactive gases. It originated from the decay of isotopes of barium, strontium, and lanthanum. This was reported on August 26 by news agency Interfax with reference to the Federal Service for Hydrometeorology and Environmental Monitoring of Russia (Roshydromet).
According to Interfax, the Northern Territorial Administration for Hydrometeorological and Environmental Monitoring (Roshydromet unit), when monitoring the environment from 8 to 23 August, while analyzing samples of radioactive fallout and aerosols, found technogenic short-lived radionuclides of barium, strontium, and lanthanum. Currently, according to Roshydromet, there are no radioactive particles in the air of Severodvinsk.
The explosion at a military facility off the coast of the White Sea in Arkhangelsk oblast occurred in the morning of August 8. In the middle of the day, the administration of Severodvinsk reported an increase in the radiation background. Representatives of the Northern Territorial Administration for Hydrometeorological and Environmental Monitoring, MOE, and the Ministry of Defence refused to comment on the situation. Rosatom State Corporation reported the death of five employees accompanying the radioisotope battery. Two other employees of the Ministry of Defence allegedly died. Due to the lack of information on the day of the explosion, residents of Severodvinsk bought up iodine preparations in pharmacies.
Some days the explosion, several monitoring stations of the Comprehensive Nuclear-Test-Ban Treaty Organization were partially shut down in Russia. Russian officials referred to some connection issues.
The government of Arkhangelsk oblast examined 110 people who provided first aid to victims of the explosion and did not find the consequences of radiation exposure. During the work they were not warned about the radiation danger.