Objectives: The aim of this study was to assess exposure to airborne endotoxins and peptidoglycans (PGs) as well as possibility of using PGs as a surrogate measure of bacterial exposure in workplaces in a metal processing plant. Material and Methods: Personal dosimetry (N = 11) was used to obtain data on concentrations of viable bacteria, total number of bioaerosol particles, endotoxins and peptidoglycans. To investigate the size distributions of aerosol particles responsible for transport of endotoxins and PGs, air samples (N = 5) were additionally collected using the 8-stage cascade impactor. Endotoxins and PGs were assayed with the Limulus amebocyte lysate (LAL) test and a kinetic version of the silkworm larvae plasma (SLP) test, respectively. Results: Median concentrations of airborne PGs (14.6 ng/m³), endotoxins (0.2 ng/m³), viable bacteria (1.16×10³ CFU/m³) and the total number of bioaerosol particles (1.81×10⁶ cells/m³) were determined. Qualitative analysis revealed presence of 19 bacterial species belonging to 14 genera. The calculations showed strong, significant correlations (p < 0.05) between endotoxins, viable bacteria (r = 0.75) and the total number of bioaerosol particle concentrations (r = 0.76) as well as between PGs and the total number of bioaerosol particle concentrations (r = 0.72). Size distribution analysis showed that the highest concentrations of bacterial aerosols occurred in the range of 2.1–3.3 μm. In the case of endotoxins, an increase of concentrations in 2 ranges of aerodynamic diameters: 1.1–3.3 μm and 5.8–9 μm was shown. For PGs there was a visible gradual increase of their concentrations in the range 2.1–9 μm. Conclusions: Peptidoglycans can be treated as a supporting indicator of bacterial contamination in metal processing plants, particularly when an assessment of an immunotoxic potential of microbiological hazards needs to be performed. However, to be extrapolated to other occupational and non-occupational environments, the obtained results require a further verification.