Impact of preventive measures on welding fume exposure among welders, robot operators, and bystanders: Air and biomonitoring.

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 trends. Powered air-purifying respirators provided low effective protection and point exhaust ventilation was more efficient than alternative solutions.

CONCLUSION

Comprehensive preventive measures reduced welding aerosol exposure across worker groups. Continued improvements are needed to ensure long-term protection for welders and bystanders.