Occupational exposure to 4,4'-bipyridyl vapor and aerosol during paraquat manufacturing.

The mass concentrations of both vapor and aerosol phases of 4,4'-bipyridyl were determined by a glass fiber filter and an XAD-2 tube in a paraquat factory. The size distributions of 4,4'-bipyridyl aerosols and particles < 10 microns were measured by a six-stage cascade impactor. The mass concentrations of 4,4'-bipyridyl aerosols were in the range of 81.9 to 159.9 mg/m3 with an average 4,4'-bipyridyl vapor mass concentration of 3.1 mg/m3 at the top of the open tank. On the average, the mass ratio of vapor phase to aerosol phase of 4,4'-bipyridyl was 0.025. Therefore, the aerosol phase is the major form of 4,4'-bipyridyl exposure to the workers in this environment. From the 4,4'-bipyridyl concentrations measured by the sampling systems of an XAD-2 tube alone and a filter followed by an XAD-2 tube, the 4,4'-bipyridyl aerosol collection efficiency of the XAD-2 tube was found to be approximately 50%. The average mass concentrations of less than 10 microns aerosols and 4,4'-bipyridyl aerosol in the occupational environment were 0.42 mg/m3 and 1.26 micrograms/m3, respectively. The mass median aerodynamic diameter (geometric standard deviation) of particles < 10 microns and 4,4'-bipyridyl aerosol are 3.50 microns (2.35) and 3.47 microns (2.58), respectively. The major mass fraction of 4,4'-bipyridyl aerosol occurred in the 3.3-5.8 microns size range. The enclosure efficiencies of a hood cover attached to a suction tube were found to be 88% and 82% for both aerosol and vapor phases of 4,4'-bipyridyl, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)