Authors present findings on 14 cases of professional bone fluorosis in metallurgists who have worked at the electrolytic production of aluminium in the plant built in the Žiar basin in Slovakia for 17.71 ± 7.67 years (x ± SD). The plant, which started the production in 1953, has not fulfilled hygienic conditions for health protection. Fluoride concentrations in the working environment were tested irregularly and varied from 1.25 to 1.7 mg . m-3, being even 5 mg . m-3 in some samples, fluoride concentrations in urine were 20.2–491.1 μmol. l-3 before the work shift in the morning. The average age at diagnosing fluorosis in the stage I and higher was 57.93 ± 7.95 years. All cases were reported as occupational diseases after taking professional history and clinical examination, necessary hematological and biochemical laboratory tests (the decreased level of ionized calcium in serum was found), including evaluation of the fluoride content in urine which was 236.06 ± 121.6 μmol. l-1 and exceeded the limit for nonexposed population 3.8 times. X-rays of long bones, LS backbone and pelvis were evaluated in collaboration with specialists in radiodiagnostics and an orthopedist. Eight cases of bone fluorosis were reported in men 60 years old and older ones. First cases were reported in 1965. There were 9 cases of fluorosis in the stage I, 3 cases of fluorosis in the stage II, 2 cases were classified as the stage II–III. The typical X-ray findings were increased bone density, a compact part of long bones was roughen on the expenses of a core cavity, ossification of membrana interossea between radius and ulna, between tibia and fibula, exostoses of muscle attachments at foramen obturatorium, ossifications of the ligamentum sacrotuberale, ossifications at spina iliaca anterior; pseudoperiostosis at lower edge of ribs was found only in one patient. The overal fatigue was found in the half of the group, sensomotor polyneuropathy of extremities in two thirds of the group, chronic bronchitis in six metallurgists, including two smokers, dyspepsia in three cases. Five men complained about milder backache and difficulties at walking, three men reported arthralgia of big joints, the rheumatic origin was excluded. Neither bone fluorosis nor some osteoarthrotic changes did not result in significant reduction of motility. In the time of reporting occupational diseases, six metallurgists were already pensioners, four ones were excluded from the risk, four ones younger than 48–53 years with the stage I fluorosis worked on even after reporting an occupational disease as metallurgists. Eleven diseases were reported until 1991. The plant was undergoing the reconstruction, substantially in 1995. Last three cases of fluorosis in the stage I has occured in 2000–2001. Patients were followed on at the clinic of occupational diseases, fluoride values in urine were low in all cases after the exposure was cut for a half year. Only in two cases of fluorosis of the stage I, a certain decline of a bone density was found on the X-ray after two years, however, it was not possible to exclude the process of demineralization related to the age and decline of physical activity. The disease was evaluated by a low financial compensation of the lower the social application according to the legislation in the Slovak Republic implemented in 2003 which was due to mild late clinical symptoms which occured at the time the metallurgists were already pensioners. Currently, the occurrence of bone fluorosis from professional exposure is an exemption in the European region. The authors presume that the new production of aluminium from 1995 and preventive projects will ensure that the occurrence of bone fluorosis will be the history in Slovakia.

        Key words: 14 cases, electrolytic production of aluminium, Slovakia, clinical picture, fluoride in urine, X-ray of skeleton, ionized calcium in serum