THE VARIABILITY OF EXPOSURE OVER TIME: A PROSPECTIVE LONGITUDINAL STUDY

摘要

Four hundred and forty personal air measurements were carried out on 54 workers, employed in the main processes in six different factories (6-13 in each). Potential exposure was to lead, benzene and dust. Ten randomly repeated hygiene surveys were carried out over 1 year. In order to estimate the magnitude of the variability in workers' exposure over time, its sources, the variance between workers and the variance within a worker, a nested unbalanced analysis-of- variance model was fitted to the log-transformed data. Of the total exposure variance, the within variance of a worker's exposure over time was 51/100 (geometrical standard deviation, GSD = 3.1) and the between workers, factories and air contaminants variance was 49/100.