The health status of some 6,000 workers from Latvia who went to clean-up the Chernobyl Nuclear Power Plant (CNPP) site following the explosion on 26 April 1986 has been analyzed. The data on these workers have been recorded in the Latvian State Register of Occupational disease patients and people exposed to ionizing radiation due to Chernobyl NPP accident (Latvian State Register) that was established in 1994. From these data, estimates have been made of external ionizing radiation to which these workers were exposed together with observations on the impact of exposure to heavy metals (especially lead and zinc) and radioactive isotopes released during the reactor 'meltdown'. These factors along with psycho-emotional and social-economic stresses account for a marked excess of mortality and morbidity in the group of CNPP accident clean-up workers compared with that of the non-exposed normal Latvian population adjusted for age and sex. The number of diseases or conditions in the CNPP accident clean-up workers has progressively risen from an average of 1.3 in 1986 to 10.9 in 2007. This exceeds for the Latvian population when adjusted for age and sex. The most serious conditions affect the nervous, digestive, respiratory, cardiovascular, endocrine (especially thyroid) and immunological systems. While the morbidity associated with diseases of the respiratory and digestive systems has decreased in recent years that in the other systems is increasing. In recent years, there has been an increased occurrence of cancers affecting the thyroid, prostate and stomach. Clinical and laboratory investigations suggest that surviving CNPP accident clean-up workers exhibit signs of immuno-inflammatory reactions causing premature aging with evidence of autoimmune diseases and immunological deficiencies or abnormalities. It is suggested that the CNPP accident clean-up workers may have a specific syndrome, the 'Chernobyl post-radiation neurosomatic polypathy', due to sustained oxidant stress injury, as a result of exposure to radiation and lead.

(RR= 1.82,) is also associated with this outcome, although nonsignificantly. Distinguishing stress-related from radiation-induced effects in this data set was difficult and these findings should provide a basis for later hypothesis testing in other cohorts. Environ Health Perspect 105(Suppl 6): 1539-1544 (1997)

Epidemiologic studies on the health effects of the Chernobyl disaster have focused largely on physical health, whereas the psychological consequences have received little attention. The authors have assessed the associations of various exposure variables with mental and psychosomatic distress in a sample of 1412 Latvian liquidators drawn from the State Latvian Chernobyl Clean-up Workers Registry. The outcome was a mixed mental-psychosomatic disorder occurring during 1986 to 1995. Comparisons among subgroups of the cohort classified according to exposure type or level were based on the proportional hazards model. Length of work (> or = 28 days) in a 10-km radius from the reactor (relative risk [RR] = 1.39, 95% confidence interval [CI] 1.14-1.70), work (> 1 time) on the damaged reactor roof (RR = 1.46, 95% CI 1.02-2.09), forest work (RR = 1.41, 95% CI 1.19-1.68), fresh fruit consumption (> or = 1 time/day) (RR = 1.72, 95% CI 1.12-2.65) are risk factors for mixed mental-psychosomatic disorder. Construction of the sarcophagus (RR = 1.82, 95% CI 0.89-3.72) is also associated with this outcome, although nonsignificantly. Distinguishing stress-related from radiation-induced effects in this data set was difficult and these findings should provide a basis for later hypothesis testing in other cohorts.

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The paper summarises the main findings on Chernobyl Nuclear Power Plant (CNPP) accident recovery workers from Latvia and their health disturbances, which have been studied by the authors during the last two decades. Approximately 6000 persons from Latvia participated in CNPP clean-up works in 1986–1991. During their work period in Chernobyl they were exposed to external as well as to internal irradiation, but since their return to Latvia they were living in a relatively uncontaminated area. Regular careful medical examinations and clinical studies of CNPP clean-up workers have been conducted during the 25 years after disaster, gathering knowledge on radiation late effects. The aim of the present review is to summarise the most important information about Latvian CNPP clean-up worker health revealed by thorough follow-up and research conducted in the period of 25 years after the accident. This paper reviews data of the Latvian State Register of Persons Exposed to Radiation due to CNPP Accident and gives insight in main health effects found by the researchers from the Centre of Occupational and Radiological Medicine (Pauls Stradiņš Clinical University Hospital) and Rīga Stradiņš University in a number of epidemiological, clinical, biochemical, immunological, and physiological studies. Latvian research data on health condition of CNPP clean-up workers in the late period after disaster indicate that ionising radiation might cause premature ageing and severe polymorbidity in humans.