Characterization of metalworking fluid aerosols in bearing grinding operations

The concentrations and size distribution of metalworking fluid aerosols were investigated in grinding operations in the bearing manufacturing industry. Fifteen paired open- and closed-face cassette samples and five cascade impactor samples were obtained in each of three types of grinding machinery (face, microcentric, and progressive). Aerosol mass concentration as measured by open-face filter sampling ranged from 0.34 to 2.43 mg/m3. As measured by closed-face sampling the range was 0.14 to 2.01 mg/m3. For each grinding process, open-face concentration was significantly higher than the closed-face concentration (paired t-test, p <0.05). Mass median aerodynamic diameter (MMAD) ranged from 3.33 to 6.26 microm. The percentage of mass greater than 9 microm ranged from 8.0 to 45.3. The MMAD and fraction greater than 9 microm were significantly greater for the aerosol produced by the face grinder compared with the other two processes. The results indicate that (1) closed-face sampling results in a lower aerosol mass concentration, as compared with open-face sampling, with the degree of difference being somewhat dependent on grinding process; and (2) the particle size distribution and concentration of metalworking fluid aerosols may vary with the type of grinding operation sampled.