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Workers exposure to hexavalent chromium, and observed exposure-control technologies, in a large industrial boiler-refurbishing operation using atomized alloy-spray "metallization" coating process.

Authors
Blade-L; Catalano-J
Source
American Industrial Hygiene Conference and Exposition, May 10-15, 2003, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 2003 May; :65
NIOSHTIC No.
20022856
Abstract
The National Institute for Occupational Safety and Health (NIOSH) conducted 21 field surveys in selected industries, to characterize workers' exposure to hexavalent chromium-containing airborne particulate and evaluate existing-control technologies. Hexavalent chromium (Cr[VI]) is a respiratory irritant, and chronic inhalation may cause lung cancer. Primary evaluation methods included collection of full-shift, personal breathing zone (PBZ) air samples for Cr(VI), measurement of ventilation-system performance parameters, and recording of descriptive information about processes, work practices, and personal protective equipment. One field survey evaluated the refurbishment of a large industrial boiler at a paper mill. Inside the multi-story combustion chamber of the boiler, abrasive blasting was used to remove corrosion from the surfaces of the steam tubing surrounding the chamber and prepare the surfaces for the application of a metal-alloy protective coating. The application of this coating was performed with a "metallization" process, which uses an electric arc to melt the metal alloy, provided as a wire feed to a hand-held spray-application unit, and compressed air to atomize the molten alloy and propel it onto the surface. Process conditions oxidize some of the metallic chromium in the alloy to Cr(VI), and generate fumes, creating a potential for inhalation exposures to workers. Workers' PBZ exposures during 300-minute spray-application periods, measured outside their respirators, exceeded 1100 micrograms of Cr(VI) per cubic meter of air (Mg/m 3), far exceeding the 1 Mg/m3 NIOSH recommended exposure limit (REL). The NIOSH assigned protection factor of the painting-type supplied air respirator hoods used is only 25. Full-shift PBZ exposures to workers who remained outside the chamber during spraying, and did not wear respirators, ranged up to 47 Mg/m 3, exceeding the REL. NIOSH researchers believe that both better ventilation and more protective respirators are needed to improve worker protection.
Keywords
Workers; Occupational-exposure; Exposure-levels; Hexavalent-chromium-compounds; Airborne-dusts; Airborne-particles; Particulate-dust; Particulates; Dust-particles; Dusts; Respiratory-irritants; Lung-cancer; Breathing-zone; Air-samples; Personal-protective-equipment; Work-practices; Heavy-metals
CAS No.
7440-47-3
Publication Date
20030510
Document Type
Abstract
Funding Type
Construction
Fiscal Year
2003
NTIS Accession No.
NTIS Price
NIOSH Division
DART
Source Name
American Industrial Hygiene Conference and Exposition, May 10-15, 2003, Dallas, Texas
State
OH; WA
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