Objectives Little is known regarding the metal working subprocesses that determine exposures in the workplace primarily because their segregation from the main process is rather difficult in real-life occupational settings. The present study aimed to identify the subprocesses in a metalworks plant with high personal exposure to particulate matter (PM_2.5) metal aerosol in order to plan future risk reduction interventions.

Methods A total of eighty 8-hour PM_2.5 metal aerosol samples from the breathing zone of four workers in each of four major operations (plasma cutting, machine operating, assembling and welding) were collected in a metalwork plant in Almaty in January to June 2020. Minimal, maximal, time-weighted average PM_2.5 metal aerosol mass concentrations were recorded with TSI SidePak AM520 personal aerosol and analysed using analysis of variance (ANOVA) after normalisation.

Results The overall sampling time was 640 hours. Maximal 1 min and geometric mean PM_2.5 concentrations were 8.551 and 1.7268 mg/m³ in plasma cutting; 4.844 and 0.9343 mg/m³ in machine operating; 2.993 and 0.6898 mg/m³ in assembling; and 2.848 and 0.4903 mg/m³ in welding. Using a Tukey-Kramer test after a one-way ANOVA, plasma cutting concentrations were significantly higher compared with all other operations (F-ratio 29.6, p<0.001). The fold-range containing 95% of the total variability (R_0.95) from all samples was 12.5.

Conclusions The highest PM_2.5 concentrations were found in plasma cutting, potentially elevating the risk of systemic inflammatory effects.