Breathing-zone and aspirated welding fume exposure assessment: Fractional factorial design

A fractional factorial experimental design was utilized to investigate the effects of some welding, physiological, and environmental parameters on fume concentrations in the breathing zone. The experimental system consisted of an exposure chamber in which a thermal breathing manikin was placed to simulate a welder's exposure scenario. The parameters were amperage, electrode size, torso and head angles, breathing rate and volume, and airflow through the chamber. Fume was measured as total fume concentration outside the welding helmet, respirable fume concentrations inside and outside the welding helmet, and the aspirated fume concentration as measured using a sampler located inside the manikin's head. A total of twenty experimental runs were evaluated satisfy the experimental design. In addition to the mass-based concentrations a subset of the samples were also analyzed for metal content.;The results from the mass-based experiments were used to develop a semi-empirical model of the fume concentrations as a function of the parameters using multiple linear regression analysis. Three parameters were shown to significantly impact the fume concentrations: torso angle, electrode size, and airflow rate. For the measurements inside the helmet, the head angle was also found to be significant. Comparisons were made between the fume concentrations as measured inside and outside the welding helmet. The results indicated a safety factor associated with the use of a welding helmet. In addition, regression analysis was used to develop models for describing the "true" breathing zone concentration using samplers located in less desirable locations on a worker. The analysis of the results from the metal speciation revealed fume compositions comparable to previous studies. A human health risk assessment of occupational exposure was performed to quantify associated health risks for a series of exposure scenarios. The results from the risk assessment indicated elevated and unacceptable risk levels for both carcinogenic and non-carcinogenic agents.