Masons are faced with a serious workplace hazard when they are exposed to crystalline silica dust. Sand and aggregate materials such as concrete contain concentrated amounts of crystalline silica. When masons dry cut concrete products including masonry blocks, bricks, and concrete slabs, they are exposed to crystalline silica dust, and they may develop silicosis, a serious and incurable respiratory disease. In the past century many workers have died from exposure to crystalline silica, and it is estimated that about 250 workers die each year from silica exposure.

How High Are Masons Exposures?

Masons' exposures to crystalline silica depend on the tasks they perform:

• Masons who perform wet tasks, such as wet cutting of blocks, or laying blocks in mortar, have less potential to be overexposed.

• Masons who perform supporting tasks, such as block runners and mortar mixers, usually will not be overexposed if they avoid areas where concrete or cement dust is visibly present in the air.

• Masons who dry cut blocks or concrete frequently have dangerous exposures up to 10 times the OSHA Permissible Exposure Limit (OSHA PEL). Exposure at this level may produce lung disease over a period of 10 years or more.

• Masons who grind out existing mortar joints prior to tuckpointing brick walls can have exposures that exceed 50 times the OSHA PEL. Exposures at this level may cause lung disease over a period of several months to 10 years.

What Safe Practices Should Masons Use?

1. Water. Water is the most efficient means to control dust from cutting concrete products. Bench saws for blocks and bricks typically have ports on the upper blade guard where water supply lines can be attached. Portable saws may or may not be equipped with water supply ports. If the saw is equipped with a wet cutting capability, the mason needs to pre-plan the work to ensure that water will be available at the location while cutting, and that the connections to the water supply are made. If the saw is not equipped with wet cutting capability, an alternative is to use water supplied by a portable water tank or cart. Two workers may be needed for the task, one to operate the cutting tool, and the other to provide the water supply. Again, the mason must pre-plan the job to ensure that the materials and manpower are available to allow for wet cutting. Some abrasive cutting tools, such as grinders, can be equipped with a self contained pump which collects, filters, and reuses a small amount of water.

2. Respirators. Avoid reliance on respirators alone for protection because they are often ineffectively used and do not provide the level of protection afforded by wet cutting. However, if exposures to crystalline silica cannot be sufficiently reduced by wet cutting or ventilation, masons should wear appropriate respiratory protection. The choice of respirator depends on the level of exposure. Examples of recommended respirator selections are the following:

• Exposures up to 5 times the PEL: Disposable dust respirators.

Typical jobs--block running, erecting scaffolds, mortar mixing;

• Exposures up to 10 times the PEL: Half-mask respirators with dust cartridges.

Typical jobs--dry cut block saws, dry cut portable saws;

• Exposures up to 50 times the PEL: Full-face piece respirators with dust cartridges, quantitatively fit tested, or supplied airline respirators.

Typical jobs-use of grinders prior to tuckpointing.

All respirators, including disposable dust "masks", must be approved by NIOSH (National Institute of Occupational Safety and Health). Additionally, a respiratory protection program must be implemented, to ensure that respirators are used safely. For a model respiratory protection program, see the appendix titled "Respiratory Protection".

3. Training Workers. Before workers begin tasks where they may be exposed to crystalline silica dust, they must be trained so that they understand the hazards of silica dust and how to protect themselves. Tool box training materials, in Spanish and English, are included in the appendix titled "Silica Training".

4. Architectural Specifications. Masons should be aware that architectural specifications for block work often contain the requirement that masonry units be laid in a dry condition. This requirement should not prevent a mason from using a wet cutting saw. Meet with the general contractor to set out work practices for block cutting that will not overexpose the mason to silica dust. When possible, plan the work so that blocks can be wet cut in advance, and sufficiently dried before they are laid. During dry weather, blocks may be laid soon after they are cut; alternatively, during wet weather, they may need to be cut several hours in advance, or may need to be placed in a drying chamber.

5. Web Site Resources

• OSHA (Occupational Safety and Health Administration) at: http://www.osha.gov
• NIOSH (National Institute for Occupational Safety and Health) at: http://www.cdc.gov/niosh/silicpag.html
• The Georgia Tech Safety and Health Consultation Program at: http://www.oshainfo.gatech.edu
• MSHA (Mine Safety and Health Administration) at: http://www.msha.gov
• eLCOSH (Electronic Library of Construction Safety and Health) at: www.cdc.gov/niosh/elcosh
• Center to Protect Workers' Rights at: http://www.cpwr.com
• American Lung Association at http://www.lungusa.org

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