Operation-specific and time-resolved monitoring of occupational nano/sub-micron particle exposure in a Swedish metal additive manufacturing facility.

The aim of the study was to determine nano/sub-micron particle and dust exposure levels throughout the whole workflow at a Swedish metal additive manufacturing (AM) facility, focusing on the laser powder bed fusion (L-PBF) method. By evaluating particle levels and composition across different AM processes using both stationary and personal sampling, the study sought to improve exposure assessment and inform protective measures in the metal AM workplaces. Measurements were conducted during five measurement weeks, as five working days Monday-Friday, between October 2020 and October 2023. Personal particle measurements in the breathing zone were performed on Mondays and Fridays for 1 to 3 workers per day. Stationary particle and dust sampling were performed continuously at three locations each week to capture task-specific and temporal variation in emissions. Nano/sub-micron particle concentrations ranged from 0 to 3.3 million particles/cm3, with the highest peaks recorded in the post-processing area. Elevated levels were also detected, near the depowdering machine, by the bandsaw, and in the lunchroom, while levels near the printers were low (<10,000 particles/cm3). Personal exposure peaks occurred during printer cleaning, feedstock powder filling, dust removal with compressed air, post-processing, and packing. In contrast to the increased nano/sub-micron particle levels observed, respirable, and inhalable dust levels were very low. The study highlights the need to monitor particle exposure during both manufacturing and post-processing. Health risks associated with airborne particles are influenced by both exposure levels and the toxicological properties of materials. To ensure a safe and sustainable future for metal AM, comprehensive exposure assessment, risk evaluation, and the implementation of protective measures remain essential.