Pulmonary toxicity and extrapulmonary tissue distribution of metals after repeated exposure to different welding fumes

Abstract

Welders are exposed to fumes with different metal profiles. The goals of this study were to compare lung responses in rats after treatment with chemically different welding fumes and to examine the extrapulmonary fate of metals after deposition in the lungs. Rats were treated by intratracheal instillation (0.5 mg/rat, once a week for 7 weeks) with gas metal arc–mild steel (GMAW-MS) or manual metal arc–hardsurfacing (MMAW-HS) welding fumes. Controls were treated with saline. At 1, 4, 35, and 105 days after the last treatment, lung injury and inflammation were measured, and elemental analysis of different organs was determined to assess metal clearance. The MMAW-HS fume was highly water-soluble and chemically more complex with higher levels of soluble Mn and Cr compared to the GMAW-MS fume. Treatments with the GMAW-MS fume had no effect on toxicity when compared with controls. The MMAW-HS fume induced significant lung damage early after treatment that remained elevated until 35 days. Metals associated with each fume sample was cleared at different rates from the lungs. Mn was cleared from the lungs at a faster rate and to a greater extent compared to the other metals over the 105-day recovery period. Mn and Cr in the MMAW-HS fume translocated from the respiratory tract and deposited in other organs. Importantly, increased deposition of Mn, but not other metals, was observed in discrete brain regions, including dopamine-rich areas (e.g., striatum and midbrain).

Keywords::

• Biodistribution
• brain
• chromium
• lung clearance
• manganese
• pulmonary toxicity
• welding fume

Acknowledgments

The authors thank Mark Millson from the Division of Applied Research and Technology in NIOSH for performing inductively coupled plasma atomic absorption spectroscopy for the project.

Declarations of interest

Disclaimer: The findings and conclusions of this paper have not been formally disseminated by NIOSH and should not be construed to represent any agency determination or policy. The authors thank the National Toxicology Program, the Manganese Health Research Program, and Dr. Richard Dey of West Virginia University for additional support and collaboration during the ongoing welding project.