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 frequency (LPALF) noise (> or = 90 dB SPL, < or = 500 Hz). The clinical picture involves extra-auditory pathology, such as neurological disturbances, respiratory disorders and cardiovascular problems. 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 occupationally simulated LPALF noise exposure on rat tracheal epithelium to determine if they could explain the symptoms found in VAD patients.

METHODS

We exposed 20 Wistar rats to occupationally simulated (8 h x d(-1), 5d x wk(-1)) LPALF noise for an accumulated total of 1236 h. The control group consisted of 10 age-matched rats, kept in equal conditions but in silence. Histological and ultrastructural studies were performed on the tracheal epithelia of both populations.

RESULTS

The most dramatic changes were identified in the ciliated cells of the exposed rats. There were frequent images of shaggy or necrotic cilia as well as regularly to partially sheared cilia. Also, there were frequent images of different stages of cilia recovery.

CONCLUSION

Occupationally simulated exposure to LPALF noise can cause important changes in ciliated cells rat tracheal epithelia. This may partially explain the clinical findings observed in VAD patients.