The authors assessed the effect of water reconstitution in the workplace by evaluating the iron status of manganese mine workers during a long-term study. Subsequent analyses and biological monitoring were performed in a group of 150 manganese miners before, and 2.8 yr after, reconstitution of drinking water in the miners' workplace. The authors found significantly high concentrations of manganese in the workplace well water, as well as in the miners' blood, urine, and hair. There was a considerable prevalence of epithelial lesions, which resulted from iron deficiency, in the miners, compared with controls. The authors assessed the prevalence of iron deficiency grades (i.e., I > II > III > IV) before and after water reconstitution. Reconstitution of drinking water for the ultimate attainment of healthy levels of manganese and other minerals resulted in a significant improvement in the miners' iron status and a decreased prevalence of epithelial lesions. The authors concluded that alterations in iron status may result from the cumulative effect of high levels of manganese in consumed water, as well as in airborne dust, in the workplace. Such elevated levels should be considered as an occupational hazard because they have an ability to interfere with iron absorption.