Objective:
This study assessed occupational exposure to mild steel welding fumes among manual welders, welding-robot operators, and bystanders in two Swedish manufacturing companies, and evaluated the impact of preventive measures.
Methods:
Welding aerosol was characterized by size distributions and number concentration, size-fractionated mass and metal composition, and morphology. Exposure to respirable aerosol and metals was measured at baseline and follow-up after company-led preventive measures. Different local exhaust ventilation solutions and the effective protection factor of powered air-purifying respirators were evaluated. Metals in blood and urine were assessed in exposed workers sampled on Monday and Friday at baseline and follow-up, and in an unexposed reference group.
Results:
Welding aerosol was dominated by ultrafine particles, and substantial far-field exposure highlighted potential second-hand risks. At baseline, manual welders were highly exposed, with median Mn concentrations exceeding the EU occupational exposure limit (Company 1: 68.6 μg/m3; Company 2: 146.6 μg/m3). Robot operators (Company 1: 15.3 μg/m3; Company 2: 25.2 μg/m3) and bystanders (Company 1: 10.3 μg/m3; Company 2: 16.8 μg/m3) also experienced notable exposure. Following preventive measures, Mn exposure decreased, particularly among manual welders at Company 2 (from 146.6 to 13.3 μg/m3; a 91 % reduction). Median Mn levels were below limit values for all groups at follow-up. Urinary Mn broadly reflected these [...]