title: Neurotoxicity following acute inhalation of aerosols generated during resistance spot weld-bonding of carbon steel.
abstract: Welding generates complex metal aerosols, inhalation of which is linked to adverse health effects among welders. An important health concern of welding fume (WF) exposure is neurological dysfunction akin to Parkinson's disease (PD). Some applications in manufacturing industry employ a variant welding technology known as "weld-bonding" that utilizes resistance spot welding, in combination with adhesives, for metal-to-metal welding. The presence of adhesives raises additional concerns about worker exposure to potentially toxic components like Methyl Methacrylate, Bisphenol A and volatile organic compounds (VOCs). Here, we investigated the potential neurotoxicological effects of exposure to welding aerosols generated during weld-bonding. Male Sprague-Dawley rats were exposed (25 mg/m³ targeted concentration; 4 h/day × 13 days) by whole-body inhalation to filtered air or aerosols generated by either weld-bonding with sparking (high metal, low VOCs; HM) or without sparking (low metal; high VOCs; LM). Fumes generated under these conditions exhibited complex aerosols that contained both metal oxide particulates and VOCs. LM aerosols contained a greater fraction of VOCs than HM, which comprised largely metal particulates of ultrafine morphology. Short-term exposure to LM aerosols caused distinct changes in the levels of the neurotransmitters, dopamine (DA) and serotonin (5-HT), in various brain areas examined. LM aerosols also specifically decreased the mRNA expression of the olfactory marker protein (Omp) and tyrosine hydroxylase (Th) in the olfactory bulb. Consistent with the decrease in Th, LM also reduced the expression of dopamine transporter (Slc6a3; Dat), as well as, dopamine D2 receptor (Drd2) in the olfactory bulb. In contrast, HM aerosols induced the expression of Th and dopamine D5 receptor (Drd5) mRNAs, elicited neuroinflammation and blood-brain barrier-related changes in the olfactory bulb, but did not alter the expression of Omp. Our findings divulge the differential effects of LM and HM aerosols in the brain and suggest that exposure to weld-bonding aerosols can potentially elicit neurotoxicity following a short-term exposure. However, further investigations are warranted to determine if the aerosols generated by weld-bonding can contribute to persistent long-term neurological deficits and/or neurodegeneration.
authors.affiliation: Health Effects Laboratory Division, National Institute for Occupational Safety and Health , Morgantown, WV , USA.
authors.forename: Krishnan
authors.initials: K
authors.lastname: Sriram
authors.forename: Amy M
authors.initials: AM
authors.lastname: Jefferson
authors.forename: Gary X
authors.initials: GX
authors.lastname: Lin
authors.forename: Aliakbar
authors.initials: A
authors.lastname: Afshari
authors.forename: Patti C
authors.initials: PC
authors.lastname: Zeidler-Erdely
authors.forename: Terence G
authors.initials: TG
authors.lastname: Meighan
authors.forename: Walter
authors.initials: W
authors.lastname: McKinney
authors.forename: Mark
authors.initials: M
authors.lastname: Jackson
authors.forename: Amy
authors.initials: A
authors.lastname: Cumpston
authors.forename: Jared L
authors.initials: JL
authors.lastname: Cumpston
authors.forename: Howard D
authors.initials: HD
authors.lastname: Leonard
authors.forename: David G
authors.initials: DG
authors.lastname: Frazer
authors.forename: James M
authors.initials: JM
authors.lastname: Antonini
mesh_terms: D000269:Adhesives / Q000737:chemistry; D000336:Aerosols; D000395:Air Pollutants, Occupational / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D001921:Brain / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects*; D005390:Fires; D005786:Gene Expression Regulation / Q000187:drug effects; D019570:Inhalation Exposure / Q000009:adverse effects*; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D020258:Neurotoxicity Syndromes / Q000276:immunology / Q000378:metabolism*; D009830:Olfactory Bulb / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D010084:Oxidation-Reduction; D017207:Rats, Sprague-Dawley; D013232:Steel / Q000737:chemistry; D023382:Toxicity Tests, Acute; D055549:Volatile Organic Compounds / Q000032:analysis / Q000633:toxicity; D014896:Welding / Q000379:methods
chemical_list: D000269:Adhesives; D000336:Aerosols; D000395:Air Pollutants, Occupational; D015415:Biomarkers; D009419:Nerve Tissue Proteins; D055549:Volatile Organic Compounds; D013232:Steel
keywords: Aerosols; Parkinson's disease; manganese; neurotoxicity; occupational exposure; volatile organic compounds; welding; welding fume