The study presents the generalized results of the long-term epidemiological, clinical, biochemical, cyto-genetic, and immunological studies dedicated to the mechanisms of the development of somatic pathology in the remote period in the victims of radiation accidents. The major accidents were included, i.e., Chernobyl nuclear power plant accident, radiation accidents on ships with nuclear energy devices, nuclear weapons tests, and other accidents.

The two databases were created at the Nikiforov Russian Center of Emergency and Radiation medicine (St. Petersburg) in order to monitor the health status of the victims of radiation accidents: (1) epidemiological database with sub-registries for leukosis, thyroid cancer and other cancers, (2) scientific clinical database.

The full range of all up-to-date and evidence-based clinical investigations was used including tomography, bio-and immunochemical methods, cancer markers and hormone levels assessment.

The epidemiological analysis showed that after five years following the exposure there is a significant rise in the incidence of somatic pathology across all age groups. After 10 years following the exposure 38% of clean-up workers already developed chronic diseases, while among those who were exposed to the dose of more than 25 cGy the incidence was more than 50%. Over 20 years of observation, the average number of diagnosed chronic diseases per clean-up worker increased from 1.4 to 10.6.

The most prevalent symptoms (>60%) are cardiovascular diseases, musculoskeletal and gastrointestinal diseases. From the results of cytogenetic and biochemical investigations the main pathological mechanism is the disturbance of microcirculation and endothelial dysfunction. In 60–80% of clean-up workers' muscular-skeletal diseases were diagnosed with the main manifestation and possible mechanism being an osteopenic syndrome.

The cytogenetic studies showed that across all age groups, the incidence of chromosome aberrations is significantly higher than in the control group. The assessment of cancer markers confirmed the elevated risk of developing cancer. This was accompanied by markedly elevated levels of hydrogen peroxide and other free-radical and lipid oxidation indicators in the blood.

The results of the complex epidemiological, clinical, biochemical, cytogenetic, and immunological investigation performed on the patients exposed to ionizing radiation due to a number of radiological accidents described the mechanisms of the development of somatic pathology due to radiation exposure.