Airborne Hexavalent Chromium and Particulate Matter Emissions during the Laser Cutting of Leathers

Abstract

Workers may be at risk of exposure to airborne contaminants, including hexavalent chromium (Cr(VI)) and particles of diverse shapes and sizes during the laser cutting of leathers because of the extensive chemicals employed in leather tanning processes. Desktop carbon dioxide (CO₂) laser engraving machines have gained popularity in various industries; however, airborne contaminant exposure in the laser cutting process of leathers remains unclear. This study investigated Cr(VI) and particle emissions during laser cutting/engraving of leather treated with various tanning methods. Six tanning methods (chrome 1-, chrome 2-, vegetable 1-, vegetable 2-, oil-, and alum-tanned) were studied at three laser power settings (15, 45, and 75%). A personal air sampler coupled with a sampling cassette and ISO 17075–2 evaluation were used to sample and analyze airborne Cr(VI) concentrations, respectively. Two real-time aerosol monitors were utilized to assess particulate concentrations and size distributions from 10 nm to 10 μm. High concentrations of Cr(VI) were detected in chrome-tanned leathers when the ventilation system was off, indicating the critical role of ventilation. The particle number concentrations were statistically significantly affected by various leather tanning methods and laser powers. Chrome 1-tanned leather exhibited the highest concentration of nanoparticles (<420 nm) at low (14,733 #/cm³) and medium (20,725 #/cm³) laser powers, while veg 2-tanned leather produced the highest micrometer-sized particle (>0.3 μm) concentration, over 1,600 #/cm³ at all laser powers. The medium laser power exhibited higher nanoparticles than other powers when laser cutting most tanned leathers. The higher power resulted in the generation of smaller-sized particles for chrome-, oil-, and alum-tanned leathers. These findings underscore the importance of adequate ventilation and controlled laser power settings in minimizing health risks during the leather laser cutting processes.