Wood trimmers are exposed to molds that periodically grow on timber, and may develop acute as well as chronic pulmonary function impairment. This study examined whether these acute changes in pulmonary function are predictors for a longitudinal deterioration in pulmonary function, beyond normal aging and exposure. Across-shift changes in pulmonary function, measured during a working week, were evaluated in 15 wood trimmers with a follow-up time of 27 months. Twenty-six sawmill workers, employed at the same plants as the wood trimmers, served as control subjects. The highest concentration of viable mold spores for the wood trimmers was 10(6) colony-forming units (cfu)/m3, i.e., several times higher than the corresponding value for the sawmill workers. At the follow-up, wood trimmers had a lower forced vital capacity (FVC) on average, after adjustment for age and height, compared to the sawmill workers. In addition, a correlation was found between the across-week change in forced expiratory volume in 1 second (FEV1) and the decline in FEV1 between the first and the second occasion, after adjusting for normal aging in nonsmoking wood trimmers (r2 = 84%, p