Amphibole asbestos is present in the Salau massif. Its composition varies from ferro-actinolite to actinolite. Asbestos is found in post-Hercynian slip-dip faults and crack-seal veins, which are compatible in the Pyrenees with Mesozoic hydrothermal events. The amount of asbestos contained in the faults is sufficient to explain the levels of asbestos dust measured during the former mining activity. According to different sources, the number of employees in the Salau mine varied from 150 to 600. Between 1982 and 1991, analyses were performed on sputum and/or bronchoalveolar washes on 28 patients. In 13 of these patients, the results showed significant retention of asbestos bodies, with concentrations equal to or higher than the values generally used as a reference in Europe. The occupational exposure limit of 8 hours (OEL_8hours) could be estimated for each workstation. Estimates were based in part on phase contrast microscopy (PCM) measurements. Simultaneous measurements by PCM and transmission electron microscopy (TEM) allowed for a correction. The estimated OEL_8hours have a unimodal distribution with an average of 0.05 actinolite fibers/cm³. The highest measurements (3.4%) were between 0.178 and 0.282 actinolite fibers/cm³. These occurred at the crusher and drilling sites of the work area. These results differ from those obtained in 2019 during the safety and sampling operations for asbestos detection before a drilling campaign, for which the company was supposed to take the asbestos hazard into account in its risk analysis. No asbestos fibers were observed, with TEM measurements, during the most emissive activities. Concentrations were less than 0.0048 fibers/cm³.