The outcomes of the forced oscillation technique as an independent method to assess airway obstruction confirmed the positive trend in lung function with increasing current exposure. Previously we found an increased sensitivity of this method to detect airway obstruction compared with spirometry in grain workers6 but not in chemical workers and workers exposed to inorganic dusts.10 We then suggested that an airway obstruction caused by endotoxin containing particles would extend to the peripheral airways,and be more readily detected by the forced oscillation technique. With the conventional criteria for airway obstruction only a few workers (2%–3%) were obstructive, which is much lower than in our earlier work using both techniques in European industrial workers (8% for FEV1