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Lung function decline in 4-monthly repeated spirometric measurements: due to silt aerosol exposure or decreasing
K Radon1, R Wegner, D Szadkowski
1Ordinariat für Arbeitsmedizin der Universität und Zentralinstitut für Arbeitsmedizin der Freien und Hansestadt Hamburg, Deutschland. K.Radon@lrz.uni-muenchen.de
Background:
Workers on dredgers and lighters on rivers are exposed to the inhalation of aerosols and dusts.
Objective:
The aim of this study was to investigate effects of river silt aerosol and dust exposure on the respiratory health of dredging employees.
Methods:
Six examinations were performed over a period of 2 years at 4-monthly intervals in 54 seamen with higher silt aerosol exposure and 36 controls of the same employer.
Results:
No significant differences could be observed between the groups at any time of the study but there was an unexpected significant decrease in the age-corrected expiratory vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)) and midexpiratory flow rate (MMEF(25/75)) over the six series in both groups. This may indicate a loss of effort of the participants in re-examinations since biological and technical influences were highly unlikely to be the cause of these findings.
Conclusions:
Ignoring this possible decline of effort in frequently repeated measurements may result in overestimating potential effects of occupational exposure.