The effect of chronic exposure to low frequency noise on rat tracheal epithelia

Introduction: Vibroacoustic Disease (VAD) is a multi-systemic entity caused by occupational or chronic exposure to large pressure amplitude and low fr equency (LPALF) noise (greater than or equal to 90 dB SPL, less than or equ al to 500 Hz). The clinical picture involves extra-auditory pathology, such as neurological disturbances, respiratory disorders and cardiovascular pro blems. Among the first complaints of VAD patients are coughing, bronchitis, and inflammation or infection of the oral cavity and the upper respiratory pathways. The goal of ths study was to investigate the effects of occupati onally simulated LPALF noise exposure on rat tracheal epithelium to determi ne if they could explain the symptoms found in VAD patients. Methods: We ex posed 20 Wistar rats to occupationally simulated (8 h . d(-1), 5d . wk(-1)) LPALF noise Tor an accumulated total of 1236 h, The control group consiste d of 10 age-matched rats, kept in equal conditions but in silence. Histolog ical and ultrastructural studies were performed on the tracheal epithelia o f both populations. Results: The most dramatic changes were identified in t he ciliated cells of the exposed rats. There were frequent images of shaggy or necrotic cilia as well as regularly to partially sheared cilia. Also, t here were frequent images of different stages of cilia recovery. Conclusion : Occupationally simulated exposure to LPALF noise can cause important chan ges in ciliated cells rat tracheal epithelia. This may partially explain th e clinical findings observed in VAD patients.