Health hazard evaluation report: HETA-98-0285-2989, Vermont Housing & Conservation Board, Montpelier, Vermont.
The National Institute for Occupational Safety and Health (NIOSH) received a request in 1998 from the Vermont Housing and Conservation Board (VHCB) to evaluate worker exposures to lead-contaminated dust and the dispersion of dust to surroundings associated with exterior paint removal and surface preparation. The VHCB arranged a demonstration project that included three paint removal/surface preparation methods performed by a Vermont licensed lead abatement contractor. The objective was to determine which method produced the least amount of dust exposure and dispersion. A NIOSH site visit was made in August 1998; the sampling results were provided to the VHCB in 1999. During the demonstration project workers removed exterior lead-based paint from clapboard siding of a single- family wood-frame house using three methods: dry scraping with manual sanding, wet scraping with manual sanding, and dry scraping with power sanding. NIOSH investigators conducted task-based sampling during four trials per method. Trials took place on different sections of the painted siding. Samples collected during each were for personal breathing zone (PBZ) and area airborne lead (PbA) (both NIOSH Manual of Analytical Methods [NMAM] Method 7105), lead in paint, and lead in the dispersed surface dust (PbS). PbS samples were collected using stationary dustfall collectors, each containing a clean unfolded pre-moistened hand wipe (Wash n' Dri) centered in the tray. Eight PbS samples were collected in two rows on the ground at zero, 6, 10, and 20 feet perpendicular to the siding. The mean lead concentration measured in painted surfaces was 18.7% (range for section means 4.8%- 27%). The highest PBZ PbA exposures were measured during dry scraping/power sanding with an improperly functioning (80%-blocked) HEPA vacuum dust collection system: 820 and 1600 micrograms per cubic meter (microg/m3) as task-based time-weighted averages (TWA) over 1-2 hours. PBZ PbA concentrations during dry scraping/manual sanding were lower, ranging from 29 to 160 microg/m3, and dry scraping/power sanding with a properly functioning HEPA vacuum system and wet scraping/manual sanding produced the lowest PBZ PbA results, ranging from 3.5 to 53 microg/m3, task-based TWA. The area PbA results at 10 ft from the work surfaces were low, ranging from 0.16 to 8.2 microg/m3. For all three methods, mean concentrations of PbS measured on the ground at zero ft and 6 ft from the house foundation ranged from 1300 to 7,600,000 microg/f2. After statistically controlling for distance, method, paint Pb concentration and the percent paint removed from substrate in a linear model, distance was significantly associated with PbS (p-value= < 0.0001). NIOSH investigators found that worker exposures to lead during dry scraping/power sanding without functional dust collection controls were a health hazard. Worker exposures during wet scraping/manual sanding were relatively low, but could be a health hazard if the activity is performed 8 hours or more. After paint removal, high concentrations of lead in settled dust were found at distances of zero to 10 ft from the work surfaces. Recommendations included (1) use effective engineering controls on power sanding equipment to limit lead dust exposure and dust dispersion to surroundings; (2) use respirators to reduce worker exposure to lead dust during dry scraping and power sanding until engineering and/or administrative controls are effective in reducing exposures below the OSHA PEL; and (3) use good hygiene practices.