Influence of abrasive grit size/lead concentration on dust particle size when sanding lead based paint

This research was undertaken to understand the relationship between the coarseness of the sandpaper used to remove lead based paint from a metal (steel) surface, lead concentration in a paint formulation, and the mass median aerodynamic diameter (MMAD) of the aerosolized dust generated by the sanding process. This understanding is important because it will allow for a better estimate of the lead dose to workers, currently and retrospectively, involved in lead based paint (LBP) removal. The study design used sandpaper with six different abrasive grit coarsenesses (indicated by the abrasive grit number or AGN) representing the spectrum of commercially available abrasive sanding pads with two lead concentration formulations (7.3% and 23.3% lead by weight in the dry film). A minimum of ten independent trials (a five minute sanding period using one sanding pad) were conducted in each grit/lead paint concentration formula pairing. Ten 30 second samples were collected using a TSI Inc., Aerosol Particle Sizer (APS) model 3300 in each trial. A total of 1470 samples were collected for use in developing a model which predicts the MMAD of the aerosolized dust based on the abrasive grit coarseness and the lead concentration in the paint formula. The model was validated using additional data collected during the experimental portion but not used in developing the model. A two-way analysis of variance was used to compare the mean MMAD values across the abrasive grit coarseness and lead paint formula concentrations pairings. Student's t-tests were used to determine the significance of differences in the mean MMAD values. A linear regression model was developed to compare the change in the MMAD of the particle size distribution by the change in grit and the lead concentration in the paint formula. Results indicated a strong direct relationship between the mean MMAD of the aerosol dust and the grit particle size. The MMAD value was also directly related to the lead concentration in the paint. Results of this research indicated that finer grits produce a greater percentage of the dust particles with diameters less than 10 mum potentially posing a greater risk to workers.