title: Manganese Fractionation Using a Sequential Extraction Method to Evaluate Welders' Shielded Metal Arc Welding Exposures During Construction Projects in Oil Refineries.
abstract: The National Institute for Occupational Safety and Health has conducted an occupational exposure assessment study of manganese (Mn) in welding fume of construction workers rebuilding tanks, piping, and process equipment at two oil refineries. The objective of this study was to evaluate exposures to different Mn fractions using a sequential extraction procedure. Seventy-two worker-days were monitored for either total or respirable Mn during stick welding and associated activities both within and outside of confined spaces. The samples were analyzed using an experimental method to separate different Mn fractions by valence states based on selective chemical solubility. The full-shift total particulate Mn time-weighted average (TWA) breathing zone concentrations ranged from 0.013-29 for soluble Mn in a mild ammonium acetate solution; from 0.26-250 for Mn(0,2+) in acetic acid; from non-detectable (ND) - 350 for Mn(3+,4+) in hydroxylamine-hydrochloride; and from ND - 39 micrograms per cubic meter (μg/m(3)) for insoluble Mn fractions in hydrochloric and nitric acid. The summation of all Mn fractions in total particulate TWA ranged from 0.52-470 μg/m(3). The range of respirable particulate Mn TWA concentrations were from 0.20-28 for soluble Mn; from 1.4-270 for Mn(0,2+); from 0.49-150 for Mn(3+,4+); from ND - 100 for insoluble Mn; and from 2.0-490 μg/m(3) for Mn (sum of fractions). For all jobs combined, total particulate TWA GM concentrations of the Mn(sum) were 99 (GSD = 3.35) and 8.7 (GSD = 3.54) μg/m(3) for workers inside and outside of confined spaces; respirable Mn also showed much higher levels for welders within confined spaces. Regardless of particle size and confined space work status, Mn(0,2+) fraction was the most abundant followed by Mn(3+,4+) fraction, typically >50% and ∼30-40% of Mn(sum), respectively. Eighteen welders' exposures exceeded the ACGIH Threshold Limit Values for total Mn (100 μg/m(3)) and 25 exceeded the recently adopted respirable Mn TLV (20 μg/m(3)). This study shows that a welding fume exposure control and management program is warranted, especially for welding jobs in confined spaces.
authors.affiliation: a Industrywide Studies Branch, Division of Surveillance, Hazard Evaluations and Field Studies National Institute for Occupational Safety and Health , Cincinnati , Ohio.
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Hanley
authors.affiliation: b Chemical Exposure and Monitoring Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health , Cincinnati , Ohio.
authors.forename: Ronnee
authors.initials: R
authors.lastname: Andrews
authors.affiliation: a Industrywide Studies Branch, Division of Surveillance, Hazard Evaluations and Field Studies National Institute for Occupational Safety and Health , Cincinnati , Ohio.
authors.forename: Steven
authors.initials: S
authors.lastname: Bertke
authors.affiliation: b Chemical Exposure and Monitoring Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health , Cincinnati , Ohio.
authors.forename: Kevin
authors.initials: K
authors.lastname: Ashley
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis / Q000737:chemistry; D020378:Confined Spaces; D060389:Construction Industry; D019570:Inhalation Exposure / Q000032:analysis; D008345:Manganese / Q000032:analysis* / Q000737:chemistry; D009314:National Institute for Occupational Safety and Health, U.S.; D016273:Occupational Exposure / Q000032:analysis*; D000066388:Oil and Gas Industry; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry; D014481:United States; D014896:Welding
chemical_list: D000395:Air Pollutants, Occupational; D052638:Particulate Matter; D008345:Manganese
keywords: construction; manganese fractionation; petroleum refineries; shielded metal arc welding (SMAW); stick welding; welding