Respiratory mucus transportability is impaired in foundry workers: a longitudinal study

Mucus transportability impairment can prolong the permanence of occupational inhalable noxae within ciliated airways. A reliable, non-invasive indicator of mucus transportability is the Normalized Frog Palate Transport Rate (NFPTR). The aim of this 3-year prospective study was to compare NFPTR between a group of 166 foundry workers (E) and a group of 133 power plant workers (NE). In the first and third years of the study, workers underwent: clinical examination, spirometry, NFPTR, chest radiography. In both plants, environmental concentrations of respiratory irritants were well below the limits set by the American Conference of Governmental Industrial Hygienists. Both groups were homogeneous for age and smoking habits. Mean NFPTR was significantly lower in E than in NE in the first and third years of the study, and in smokers in comparison with non-smokers, at the end of the follow-up. NFPTR impairment was significantly associated with occupational exposure in the first and third years of the study. In the third year, a decline in NFPTR was associated with exposure, smoking habits, FVC and FEV1/FVC.100. At the end of the study, the means of FVC, FEV1 and PEF were significantly lower in E. No cases of pneumoconiosis were observed. In this study, low doses of foundry respiratory irritants were associated with impairment of mucus transportability; the consequent slowing of mucociliary clearance increased internal doses of foundry airborne noxae.