Metal dust exposure strongly affects human health, especially for smelters. Little is known, however, about the impact of metal dust exposure on influenza-associated lung function decrement risk in smelters. Different body mass index (BMI) groups were also associated with respiratory diseases. The purpose of this study was to use a probabilistic risk assessment approach to explicitly link occupational metal dust exposure, BMI-correlated health effects, and influenza-associated lung function decrements to investigate potential risk among smelters. Here we showed that (i) influenza A-associated metal dust exposure in SiMn/FeMn/FeCr smelters had slightly higher health risks than that in FeSi/Si-metal's. (ii) BMI >= 35 had the highest risk in respiratory infection exacerbations, and (iii) the estimated smelting metal dust induced forced expiratory volume in 1 s (FEV1) decreasing rates were 0.59 and 1.11 m(3) mg(-1) for FeSi/Si-metal and SiMn/FeMn/FeCr smelters, respectively. Our results suggested that smelters better be aware of severe weight gains (e.g., BMIs from 27-40) because it is likely to lead to 17-25% decrements in lung function. This study provides a novel probabilistic risk assessment framework to quantitatively assess the occupational health risk posed by metal dust exposure associated with influenza infection based on BMI measures. (C) 2012 Elsevier B.V. All rights reserved.