['Aluminum potroom exposure is associated with increased mortality of COPD but the association between potroom exposure and annual decline in lung function is unknown. We have measured lung volumes annually using spirometry from 1986 to 1996. The objective was to compare annual decline in forced expiratory volume in 1\u2009s (dFEV1) and forced vital capacity (dFVC).', 'The number of aluminum potroom workers was 4,546 (81% males) and the number of workers in the reference group was 651 (76% males). The number of spirometries in the index group and the references were 24,060 and 2,243, respectively.', 'After adjustment for confounders, the difference in dFEV1 and dFVC between the index and reference groups were 13.5 (P\u2009<\u20090.001) and -8.0 (P\u2009=\u20090.060)\u2009ml/year.'] Is annual decline in forced expiratory volume steeper in aluminum potroom workers than in workers without exposure to potroom fumes?