Inhaling silica dust may cause silicosis or lung scarring with prolonged exposure.  Silicosis is an incurable, sometimes fatal, disease.  Exposure to silica also causes lung cancer and other lung diseases including chronic obstructive pulmonary disease (COPD) and tuberculosis, and has been linked to renal disease and rheumatoid arthritis.  A report by OSHA noted that studies “show that using a handheld masonry saw to cut bricks, concrete blocks and similar materials can result in hazardous levels of airborne silica if measures are not taken to reduce dust emissions.  Operating a handheld masonry saw outdoors without dust controls can produce silica exposures as high as 14 times the Occupational Safety and Health Administration’s (OSHA) benchmark of 0.1 mg/m3 (milligrams per cubic meter of air) as an 8-hour time-weighted average (TWA), an exposure approximately equivalent to OSHA’s general industry permissible exposure limit (PEL) for construction (OSHA Case Files.)  Short-term exposures or exposures from operating saws indoors can be significantly higher (up to 10 mg/m3).” (OSHA Controlling Silica Exposure in Construction – 2009)

When water is used to suppress the dust at or very near the source, dust concentrations in the worker’s breathing zone and exposures are reduced.   In some cases, particularly where work is intermittent or in an area with general ventilation, use of water may be adequate to reduce the need to wear a respirator and the need for an employer’s respiratory protection program.

• Independent published studies have found a risk reduction.
• Safety and health experts believe there is a risk reduction.

For example: The 2009 OSHA report “Controlling Silica Exposures in Construction,” referenced a study that found “respirable dust levels were reduced by up to 94 percent for pressurized portable water supply systems and up to 96% for a constant supplying water source… [and] When effective wet methods are used outdoors, it is unlikely that supplemental respiratory protection will be needed.”  (“Measurements of the effectiveness of dust control on cut-off saws used in the construction industry,” 1999 Thorpe, et.,al) The OSHA report also included NIOSH data that found “that an employee dry cutting on concrete outdoors was exposed to 1.5mg/m3 of silica as an 8-hour TWA [time-weighted-average]" and noted that “a reduction of 96% in respirable dust for this employee would have resulted in exposure around 0.06mg/m3 if the employee switched to wet methods.”  In this example, wet methods would have dropped the workers exposure below OSHA’s permissible exposure limit (PEL).  The report also states that “Wet cutting, when used properly, is an effective way to reduce employee exposures to silica dust and in most cases maintains exposures below the allowable limit.  Wet cutting is  the most effective method for controlling silica dust generated during sawing because it controls the exposure at its source.”

In addition, a study of  engineering controls, (In Depth Survey of Dust Control Technology for Cutting Concrete Block and Tuckpointing Brick, 2008, Echt et al.) observed an 88 percent reduction in respirable dust and a 90 percent reduction in respirable silica, compared to use of no control, during the use of a hand-held masonry saw with a water-spray attachment.  

Husqvarna models use a DEX® dust management system for wet and dry cutting or a "water saving wet cutting kit, which efficiently binds dust with less water usage and slurry, compared to traditional wet cutting."

Wet dust suppression increases workers’ visibility and comfort when engaged in dust producing tasks.  Improved worker visibility and comfort may in turn result in less fatigue for the worker and greater productivity.   Capturing dust at the source may also eliminate or reduce time spent cleaning up the work site and adjacent property (including cars, etc.).

• Safety and health experts believe there is an increase in productivity.

Increases in productivity are based on safety and health experts’ belief that the controls will reduce dust-related hazards, and reduce worker fatigue by improving visibility and providing a cleaner work environment.

Other items that may impact productivity include time spent cleaning up or dealing with the slurry and run-off produced, time that may be required to allow masonry materials to dry after cutting and before use, which will depend on the material, the amount of water used and the application.  In addition, gaining access to electricity or a water source may impact productivity.

STIHL
For purchasing information visit the website at www.stihlusa.com/construction/%20 or call 1-800-GO-STIHL

Diamond
For purchasing information visit the website at www.diamondproducts.com/dp_home.htmhttp://www.diamondproducts.com/dp_home.htm or call 1-800-321-5336

Husqvarna
For purchasing information visit the website at www.husqvarna.com/us/%20 or call 1-800-700-5919

To achieve maximum dust suppression and exposure reductions the equipment must be maintained and workers must be trained on the proper use of the equipment.  Use of the tools and the tasks performed must also be in compliance with applicable local, state or federal regulations.  Things to consider:

•    “Concern that excess shrinkage as the units dry might lead to cracks has led some overly cautious specifiers to prohibit wet cutting. The bottom line is that the amount of water added to the unit during site cutting is insignificant, in terms of shrinkage. This was clarified in the ACI 530.01-05/ASCE6-05/TMS 602-05 Specification for Masonry Structures. The article on wetting concrete masonry units includes this sentence: “Wet cutting is permitted.” (Source:  http://www.imiweb.org/imi_toolkit/pdf/ClarificationWetCutting.pdf)
•    The use of water-based controls may result in wet and slippery ground and walking surfaces. During cold weather this may lead to the formation of ice and increase the risk of slips, trips and falls.
•    Cutting debris that is not bagged and removed from the work area while wet may become airborne once dried, posing an inhalation hazard to anyone in the area.  A work area free of debris and excess water must be maintained to reduce the risk of these hazards.
•    The use of water as a dust control increases the risk of shock when electricity is used in the same area. Electrical cords and extensions must be rated for the tool's power requirements, be regularly inspected, replaced when damaged, and used in combination with ground fault interrupt circuits.
•    The use of gasoline-powered equipment poses the risk of carbon monoxide exposure, particularly in areas where airflow is reduced. Small, inexpensive personal monitors can be worn by the operator to warn of unacceptable exposures. Gasoline powered equipment should not be used in confined spaces or indoors.
•    Hand-held masonry saws frequently generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL), which are hazardous. Hearing protection should be worn when using masonry saws unless an industrial hygienist has conducted noise monitoring and indicated that hearing protection is not required.
•    Hand-held masonry saws frequently weigh more than 20 pounds and the heaviest exceed 30 pounds. Use of these tools will require a strong static effort which can lead to fatigue, pain and musculoskeletal disorders. Operators should take breaks on a regular basis and when fatigued. Consider having each tool and task combination evaluated by an industrial hygienist or ergonomist.