A longitudinal follow-up of pulmonary function and respiratory symptoms in workers exposed to manganese.

The purpose of the investigation was to study the effects on the respiratory system in mine workers with long-term exposure to manganese (Mn) in the workplace. The study included a follow-up of pulmonary function and respiratory symptoms among 145 workers employed in a large Mn mine and 65 matched controls, and the assessment of Mn concentrations in environment and biological samples. Lung function was measured by recording spirometric parameters. The Mn-exposed workers reported more respiratory symptoms and a significantly higher prevalence of all grades of pulmonary function impairment. All predicted symptoms except for asthma increased significantly in the current smoking group compared with the non-smoking group. There was a significant decrease in FEV1, FVC, and FEV1% values in exposed workers compared with controls at stages 2 and 3, with an additive effect of the smoking habit. The Mn concentrations in blood, urine, and hair were significantly higher in the exposed workers than in the controls. The level of cumulative exposure index of workplace Mn was notable and did not change significantly over this study. The respiratory effects found in Mn-exposed workers were probably caused by the Mn in the workplace and the synergistic effect of smoking. These effects indicate a need for respiratory protection and improvements in the work environment.