Picosecond and femtosecond laser machining may cause health risks related to nanoparticle emission

It is well known that nanoparticles are generated as by-products during ultrashort-pulsed laser ablation. Airborne nanoparticulate matter is well known as potential health risk for exposed workers. In order to provide safety-related statements on nanoparticles generated during laser micromachining, we studied the particle size distribution during laser ablation. Results on particle size distributions using femtosecond (fs) laser pulses have already been presented at last ILSC. In this study we present a comparison and risk assessment of picosecond (ps) versus fs generated airborne nanoparticles. At the same pulse energy, fs pulses release similar share of nanoparticles (>80%) in the aerosol fraction, while fs compared to ps pulses generate a far higher portion 7 nm sized particles during machining of metals (steel, brass) and ceramics (zirconia). These nanoparticles sampled at the workplace have the same chemical composition than the ablated material (iron-chromium-nickel alloy, yttria-doped zirconia). A quantitative risk assessment is carried out and compared with indicators of toxi-cological effects of inhaled nanoparticles. The surface equivalent of nanoparticles dispersed in the air of the workplace is not likely to exceed the surface dose which cause inflammatory response in animal lung. But within one 8 h shift an efficient fume extraction is strongly recommended for safe operation during fs and ps laser micromachining even in research laboratories.