Particle emission and respiratory exposure to platinum metal powders during additive manufacturing: a pilot study

Abstract

Background: Additive manufacturing (AM) utilising metal powder is associated with the emission of airborne particles of various sizes, which may result in respiratory exposure of the AM operator to this powder. Research involving platinum in AM is non-existent and the aim of this pilot study was to provide an initial understanding of the characteristics of platinum powder particles and emissions during the different process phases of AM as well as personal exposure of the AM operator to metal powders. Methods: This study was conducted over two print cycles of powder bed fusion (PBF) with platinum powder as feedstock at an AM facility. Particle size selective counting instruments were used to investigate the emissions of airborne particulates during the different phases of PBF AM in the workplace atmosphere. The particle number concentrations were used to calculate the particle emission rate during the AM process. Personal exposure to inhalable, respirable and < 300 nm sized particulates was measured and analysed using inductively coupled plasma-mass spectrometry to investigate possible metal exposure during AM. Results: In this pilot study the highest concentration of 0.01 > 1 μm sized particles was emitted during the pre-processing phase, followed by the post-processing phase and lastly the processing phase. Particles of 0.3 μm in size had the highest peak particle number concentration of 7.71 x107p/m3 during the first print cycle and 3.02 x108 p/m3 in the second print cycle, followed by 0.5 μm and 1 μm sized particles. Emission rates indicated that during pre-processing, the highest concentrations of particles were emitted (7.95 x106 p/min) followed by the processing phase and lastly the post-processing phase. Personal exposure concentrations for inhalable and < 300 nm sized platinum particles were below that of the detection limit for platinum metal analysis. However, operators were exposed to inhalable sized metals such as arsenic, cobalt, copper, lead and nickel among which cobalt, copper and nickel exceeded occupational exposure limits. Conclusion: Concentrations of particles ranging from 0.01 to 10 μm were emitted during all three AM phases. The highest emission concentration was in the pre-processing phases of print cycle 1 and print cycle 2. Emission rates were highest in the pre-processing phase over both print cycles. This pilot study indicates that future studies should focus on particle emissions rather than on personal exposure of the AM operators to platinum metal powders. Personal respiratory exposure to platinum metal powder was below the detection limit but attention should be directed to other detected insoluble metals such as arsenic, cobalt and copper of which the presence was likely engendered by workplace cross-contamination. It is the duty of the AM employer at the facility to educate AM operators to any risks that may be associated with the PBF AM process or any other workplace risk. These employers further need to implement control measures, to eliminate or reduce the risk to an acceptable level.