Assessment of the nasal mucosa in workers exposed to the prolonged effect of phosphorite and apatite dusts.

One hundred and thirty one workers occupationally exposed to phosphorite and apatite dusts and a control group underwent repeated laryngological and cytological examinations of nasal mucosa smears. The clinical examination showed chronic simple or atrophic rhinitis. The cytological test revealed metaplasia of the respiratory epithelium towards squamous epithelium in all smears. Both the rate of catarrhal changes and the degree of epithelial metaplasia varied with the duration of exposure.