Respirable crystalline silica dust exposure during abrasive blast cleaning of bridge deck surfaces.
Appl Occup Environ Hyg 1996 Feb; 11(2):81-83
The results of a study of respirable crystalline silica (14808607) dust exposures occurring during abrasive blast cleaning of bridge deck surfaces were discussed. Breathing zone samples were collected from seven abrasive blasters, six traffic controllers, nine hopper loaders, and three flaggers at two or three sites in North Carolina where bridge deck surfaces were being cleaned by abrasive blasting prior to being recoated. All blasters wore an air supplied respirator helmet. Use of respiratory protection by the other workers was less consistent. A hopper loader and traffic controller at one site wore disposable dust/mist respirators, whereas no workers except the blasters wore respiratory protection at another site. The breathing zone samples were analyzed for respirable dust and crystalline silica. The silica content of the respirable dusts at the worksites varied from 7.1 to 37.5%. Time weighted average (TWA) respirable silica exposures of the abrasive blasters at two sites varied from 0.02 to 0.20mg/m3. Exposure times varied from 91 to 168 minutes (min). No respirable silica was found in samples collected at the third site. TWA respirable silica exposures of the traffic controllers at the three sites varied from 0.05 to 0.53mg/m3 for exposure times of 79 to 299min. TWA respirable silica exposures of the hopper loaders varied from 0.04 to 0.35mg/m3 and the exposure times varied from 83 to 308min. The TWA respirable silica exposures of two flaggers at one of two worksites were both 0.02mg/m3. No silica was detected in the breathing zone of a flagger at the second site. The author concludes that all of the blast crews at the worksites had the potential for exposure to significant concentrations of respirable silica dust. Recommendations include having all employees including flaggers, even though they are usually located some distance from the actual blasting site, wear respiratory protection and performing real time monitoring of respirable silica dust exposures.
NIOSH-Author; Silica-dusts; Occupational-exposure; Abrasive-blasting; Road-construction; Workplace-monitoring; Respirable-dust; Respiratory-protective-equipment
David Lipton, North Carolina Department of Environmental Health and Natural Resources, Occupational and Environmental Epidemiology Section, P.O. Box 27687, Raleigh, North Carolina 27611-7687
Applied Occupational and Environmental Hygiene