The report indicates that sources of ionizing radiation, such as radon, thoron, cosmic rays, as well as natural radioactive substances in soil and food, constitute the main part of the radiation burden on humans. Anthropogenic sources generally contribute significantly less, except for rare major radiation accidents.
Experts estimate that the average global annual effective dose of exposure from natural sources is approximately 3.0 millisieverts. This is primarily due to inhalation of radon and its decay products, which accounts for about 1.8 millisieverts per year. The second largest contribution comes from radionuclides ingested through food and water, as well as external radiation from radionuclides present in the Earth's crust and outer space.
Interestingly, this level of exposure has been found to be higher than the previous estimate published in 2008, which was 2.4 millisieverts. However, UNSCEAR notes that this increase is not due to a rise in environmental radiation, but rather to improvements in data collection and analysis methods.
As for anthropogenic sources of radiation, such as medical, scientific, and industrial applications, their contribution under normal operating conditions is only a few microsieverts per year.
Residents living near nuclear power plants are also subjected to minimal exposure, which typically does not exceed several tens of microsieverts per year.
The report also mentions that radiation levels in areas where nuclear tests were conducted have significantly decreased. While radiation levels were high at the beginning of the tests, annual doses at the test sites in New Mexico, the Marshall Islands, and other locations are now generally lower than the natural background.
Regarding the Chernobyl and Fukushima accidents, radiation levels in these areas continue to decrease due to radioactive decay and natural processes, as well as decontamination measures. Currently, annual doses near Chernobyl range from tens of microsieverts to several millisieverts, while in non-evacuated municipalities near Fukushima, they range from a few microsieverts to approximately 0.3 mSv.
The UNSCEAR report is intended to provide governments and international organizations with relevant scientific data to assist in the formulation of policies in the field of radiation protection and public health.
