title: Changes in blood manganese concentration and MRI t1 relaxation time during 180 days of stainless steel welding-fume exposure in cynomolgus monkeys.
abstract: Welders are at risk of being exposed to high concentrations of welding fumes and developing pneumoconiosis or other welding-fume exposure-related diseases. Among such diseases, manganism resulting from welding-fume exposure remains a controversial issue, as although the movement of manganese into specific brain regions has been established, the similar movement of manganese presented with other metals, such as welding fumes, has not been clearly demonstrated as being similar to that of manganese alone. Meanwhile, the competition between Mn and iron for iron transporters, such as transferrin and DMT-1, to the brain has also been implicated in the welding-fume exposure. Thus, the increased signal intensities in the basal ganglia, including the globus pallidus and subcortical frontal white matter, based on T1-weighted magnetic resonances in welders, require further examination as regards the correspondence with an increased manganese concentration. Accordingly, to investigate the movement of manganese after welding-fume exposure, 6 cynomolgus monkeys were acclimated for 1 mo and assigned to 3 dose groups: unexposed, low dose of (total suspended particulate [TSP] 31 mg/m3, 0.9 mg/m3 of Mn), and high dose of total suspended particulate (62 mg/m3 TSP, 1.95 mg/m3 of Mn). The primates were exposed to manual metal-arc stainless steel (MMA-SS) welding fumes for 2 h/day in an inhalation chamber system equipped with an automatic fume generator for 6 mo. Magnetic resonance imaging (MRI) studies of the basal ganglia were conducted before the initiation of exposure and thereafter every month. During the exposure, the blood chemistry was monitored every 2 wk and the concentrations of metal components in the blood were measured every 2 wk and compared with ambient manganese concentrations. The manganese concentrations in the blood did not show any significant increase until after 2 mo of exposure, and then reached a plateau after 90 days of exposure, showing that an exposure period of at least 60 days was required to build up the blood Mn concentration. Furthermore, as the blood Mn concentration continued to build, a continued decrease in the MRI T1 relaxation time in the basal ganglia was also detected. These data suggested that prolonged inhalation of welding fumes induces a high MRI T1 signal intensity with an elevation of the blood manganese level. The presence of a certain amount of iron or other metals, such as Cr and Ni, in the inhaled welding fumes via inhalation was not found to have a significant effect on the uptake of Mn into the brain or the induction of a high MRI T1 signal intensity.
authors.affiliation: Center for Occupational Toxicology, Occupational Safety and Health Research Institute, Korea.
authors.forename: Jae Hyuck
authors.initials: JH
authors.lastname: Sung
authors.forename: Choong Yong
authors.initials: CY
authors.lastname: Kim
authors.forename: Seoung Oh
authors.initials: SO
authors.lastname: Yang
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Khang
authors.forename: Hae Kwan
authors.initials: HK
authors.lastname: Cheong
authors.forename: Jong Seong
authors.initials: JS
authors.lastname: Lee
authors.forename: Chang-Woo
authors.initials: CW
authors.lastname: Song
authors.forename: Jung Duck
authors.initials: JD
authors.lastname: Park
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Han
authors.forename: Yong Hyun
authors.initials: YH
authors.lastname: Chung
authors.forename: Byung Sun
authors.initials: BS
authors.lastname: Choi
authors.forename: Il Hoon
authors.initials: IH
authors.lastname: Kwon
authors.forename: Myung Haeng
authors.initials: MH
authors.lastname: Cho
authors.forename: Il Je
authors.initials: IJ
authors.lastname: Yu
mesh_terms: D000395:Air Pollutants, Occupational / Q000737:chemistry / Q000633:toxicity; D000818:Animals; D001273:Atmosphere Exposure Chambers; D001479:Basal Ganglia / Q000187:drug effects* / Q000378:metabolism; D002857:Chromium / Q000032:analysis / Q000097:blood; D004305:Dose-Response Relationship, Drug; D019570:Inhalation Exposure; D007501:Iron / Q000032:analysis / Q000097:blood; D008252:Macaca fascicularis; D008279:Magnetic Resonance Imaging; D008297:Male; D008345:Manganese / Q000032:analysis / Q000097:blood / Q000378:metabolism; D009532:Nickel / Q000032:analysis; D052638:Particulate Matter / Q000737:chemistry / Q000633:toxicity*; D013193:Stainless Steel; D013997:Time Factors; D014896:Welding
chemical_list: D000395:Air Pollutants, Occupational; D052638:Particulate Matter; D002857:Chromium; D013193:Stainless Steel; D008345:Manganese; D009532:Nickel; D007501:Iron