ABSTRACTChronic fluorosis is a slow and progressive process causing symptoms related to several systems particularly musculo-skeletal and dental systems. This study is aimed at investigating the biochemical and histological effects of chronic fluorosis on first generation (F1) rat lung tissues.Adult Wistar albino rats were used in order to obtain F1 male rats. Female rats were mated with males at a 2:1 ratio. The pregnant rats were given drinking water containing 100 mg/L sodium fluoride during gestation period. The rats had labour at 21±2 days. During the lactation period the mother rats were given the similar fluoridated water (100 mg/L fluoride). After weaning period, the young animals (1st generation; F1) were given the similar fluoridated water for 4 months time. Then, 9 male rats (F1) were chosen randomly and were sacrificed, and the lungs were removed for biochemical and histological examination. Control group rats were given commercial water containing of 0.07 mg/L fluoride.In F1 rats, plasma fluoride levels and the levels of thiobarbituric acid reactive substance (TBARS) in the homogenates of lung tissues were found to be increased significantly when compared with the control group. There were markedly histological changes in lung tissues of F1 rats. Alveolar congestion, descuamation of alveolar epithelium, thickened interalveolar septae were observed. Mononuclear cell infiltrations and hyperemic vessels were evident in the parenchymal areas. Moreover, some emphysematous areas were observed. Our biochemical and histopathological results clearly show that chronic fluorosis causes a marked destruction in lung tissues of F1 rats.