Abstract
Following the diagnosis of two cases of occupational asthma among dental technicians, an industrial hygiene survey was conducted in two dental laboratories to determine time-weighted average and peak concentrations of methyl methacrylate vapor and time-weighted average concentration of acrylic dust. The time-weighted average concentrations of methyl methacrylate vapor were 0.7 ppm and 1.6 ppm and average peak concentrations were 9.3 ppm and 9.7 ppm for the first and second laboratory, respectively. The use of a local exhaust ventilation system was significant in reducing the peak concentration of methyl methacrylate vapor in the breathing zone of dental technicians. However, the local exhaust ventilation was not efficient in reducing the concentration of airborne acrylic dusts. Occupational exposure of dental technicians to dental materials, in particular to methyl methacrylate, requires further investigation. Local exhaust ventilation systems can reduce the concentration of methyl methacrylate in the dental laboratories to a significant extent if installed and used properly.