Prevalence of middle ear disorders in coal miners.

Abstract

Results are presented from a study of the prevalence of middle and external ear disorders in coal miners who work underground. The study followed from an earlier NIOSH report (1976) that indicated a possibly large number of otoscopic abnormalities in this population of workers. Otoscopic examinations, pure tone air- and bone-conduction audiometry tests, and impedance tests were administered to 350 underground miners and 150 industrial workers not associated with mining. The study was conducted completely within a hospital otolaryngology/audiology clinic setting. Results of the investigation showed a highly similar prevalence of middle ear and ear canal abnormalities in the miner group and the control group (19 percent). Middle ear abnormalities observed in the miners were judged by the examining otolaryngologists to have preceded their experience in the mines and were not related solely to underground noise exposure or coal dust. Nearly half of the subjects who had an air-bone gap had no middle ear abnormality observable by otoscopic examination. There was substantial agreement between the finding of abnormal otoscopy and abnormal tympanometry. By itself, acoustic reflex was not useful in identifying middle ear disorders, since this reflex may be absent for other reasons, including presence of severe sensorineural hearing loss.