Straight to PEL

Donald E. Smith, CCS

July 2007

I received a telephone call from an insurance company with concerns about silica sand in drywall and the potential exposure to drywall finishers during the sanding process. It seems that one of their adjusters had visited a job site and discovered from reading the Material Safety Data Sheets for the drywall that the particular brand in use contained silica sand. This discovery lead to concerns about the health and well being of the finishers involved and therefore the exposure of the insurance company to potential liability. Their question was, What precautions should be taken to reduce or eliminate the finishers’ exposure to silica dust?

A quick bit of research revealed that the National Institute for Occupational Safety and Health, a unit of the Center for Disease Control, conducted a Health Hazard Evaluation in 1994 and found that drywall sanders were exposed to as much as 10 times the permissible exposure limit of 15mg/m3 for total dust set by the Occupational Safety and Health Administration. The OSHA PEL for respirable dust (5mg/m3), the very small particles that can go deep into the lungs, was also exceeded.

Joint compound manufacturers recognize the exposure exists and have included warning in their MSDSs to avoid generating dust and to use respiratory protection while sanding. Another suggestion is to use wet sanding whenever possible, and yet another was to cut exposures by ventilation.

Several lightweight sanding systems are now sold to control drywall workers’ sanding exposures. These systems use portable vacuums to capture and remove the dust before the worker is exposed to it. In 1994, NIOSH studied several of these sanding systems at the International Brotherhood of Painters and Allied Trades Apprenticeship Training Facility in Seattle. NIOSH engineers compared the dust exposures from three pole-sanding and two hand-sanding vacuum control systems with the exposures from traditional, non-ventilated sanding methods. The five commercially available vacuum sanding controls successfully reduced dust exposures by 80 percent to 97 percent. Four of the five sanding controls cut exposures by nearly 95 percent. If engineering controls had reduced total dust exposures by 90 percent in the HHE case report described earlier, the construction workers’ exposures would have remained below the OSHA PEL.

In addition to lower exposures, vacuum sanding systems can help the sander, subcontractor, general contractor and building owner in other ways. The dramatic reduction in airborne dust exposures results in a much cleaner work area during and after sanding. For workers, the clean working environment is more comfortable. For the subcontractor, a comfortable worker is likely to be more productive, be absent less often and require fewer breaks for fresh air. The savings and reduced regulatory liability given by lower respiratory protection requirements will be passed from the subcontractor to the building owner. Other cost savings will result from a cleaner environment that reduces dirt, cleanup time and repair or repainting of stained floors and carpets.

NIOSH study results suggest that construction workers’ dust exposures might be cut simply by changing from hand-sanding to pole-sanding. This change is even more important when working overhead. The pole increases the space between the worker and the sanding surface, which in turn reduces the amount of dust close to the worker’s nose and mouth.

For free information about controlling this hazard or for information about other occupational health and safety issues, call NIOSH at (800) 35.NIOSH or go to http://www.cdc.gov/niosh/homepage.html.

NIOSH report HETA 94–0078–2660 and a list of known sources for drywall sanding engineering controls may be requested from NIOSH. A drywall sanding kit may be requested from the Center to Protect Workers Rights by calling (202) 962.8490.

About the Author
Donald E. Smith, CCS, is AWCI’s director of technical services. Send your technical questions to him at smith@awci.org, or call him at (703) 538.1611.