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Inhalation of a spot welding aerosol using an adhesive increased airway resistance but not lung inflammation.

Antonini JM; Afshari A; Thompson JA; Fedan JS; McKinney W; Meighan TG; Jackson MC; Chen BT; Schwegler-Berry D; Erdely A; Frazer D; Zeidler-Erdely PC
Toxicologist 2013 Mar; 132(1):44
Spot welding (SW) is used in the automotive and aircraft industries where high speed repetitive welding is needed and relatively thin metal sections are welded. Epoxy adhesives are applied as sealers to the seams of the metals that are joined. SW produces complex aerosols composed of both metal and volatile compounds which may cause bronchitis and asthma in workers. The goal was to assess the effect of SW fumes on lung function and toxicity. Male Sprague-Dawley rats were exposed by inhalation to 20 mg/m3 of SW aerosol in the presence of an adhesive for 4 hr/d x 8 d. Controls were exposed to air. Size distribution of the aerosol as determined by a MOUDI particle impactor was tri-modal with a MMAD of 1.66 microm in the large-fine mode, 0.30 microm in the small-fine mode, and 0.01-0.05 microm in the ultrafine mode. Two distinct particle morphologies were observed- a brownish metal particle that predominated in the small-fine particle fraction and a black, glue-like particle that was in the large-fine fraction. The metal fraction was found to be >90% Fe. Significant amounts of volatiles (e.g., benzene, toluene, others) were present, likely produced from the vaporization of the adhesive. At different times after exposure, bronchoalveolar lavage (BAL) was performed to assess lung toxicity. Lung resistance (RL) was evaluated in a separate set of animals before and after challenge with inhaled methacholine (MCh). Immediately after exposure, baseline RL was significantly elevated in the group exposed to the SW fumes. Basal RL returned to control level by 1 d after exposure. Reactivity to MCh was not affected at any time point after fume exposure. No significant increase in lung inflammation (neutrophil influx) or injury (cytotoxicity and lung epithelial permeability) was observed in BAL fluid at 1 and 5 d after exposure to SW fume. Acute inhalation of SW fumes at occupationally-relevant concentrations may act as an irritant as evidenced by the increased RL but had little effect on toxicity.
Toxicology; Aerosols; Laboratory-animals; Exposure-assessment; Exposure-levels; Inhalation-studies; Pulmonary-function; Pulmonary-system; Lung-function; Dose-response; Lung-irritants; Welding; Welders; Automotive-industry; Aircraft; Epoxy-compounds; Epoxy-resins; Adhesive-bonding; Adhesives; Sealing-compounds; Metal-compounds; Volatiles; Bronchial-asthma; Metal-fumes; Welders-lung; Morphology; Iron-compounds; Alveolar-cells; Airway-resistance; Methacholines; Fumes
7439-89-6; 71-43-2; 108-88-3
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The Toxicologist. Society of Toxicology 52nd Annual Meeting and ToxExpo, March 10-14, 2013, San Antonio, Texas
Page last reviewed: April 1, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division