NIOSH-Funded Studies Show Ways to Reduce Silica Exposure in Concrete Cutting

The pneumatic drill generated 444 times the OSHA permissible exposure level of silica dust, while the electric drill generated 11 times the OSHA level. The pneumatic drill's noise level was also greater than that of the electric drill, according to one study highlighted in NIOSH's October 2018 Research Rounds.

Drilling into concrete can expose workers to silica dust, which will damage workers' lungs if inhaled, and the drilling also exposes the worker to hand vibration and noise at levels above recommended limits. Two NIOSH-funded studies through CPWR–The Center for Construction Research and Training and the University of California at Berkeley have identified ways to reduce these hazards, NIOSH reported in its October 2018 Research Rounds.

One study used a new robotic system to measure productivity and the silica dust, handle vibration, and noise exposures from using electric and pneumatic drills. When testing drills without engineering controls such as a vacuum or water to reduce dust levels, investigators found similar productivity between the drills, but much higher vibration, dust, and noise levels with the pneumatic than the electric drill. Vibration levels were more than five times greater with the pneumatic than the electric drill. The pneumatic drill generated 444 times the OSHA permissible exposure level of silica dust, while the electric drill generated 11 times the OSHA level. The pneumatic drill's noise level was also greater than that of the electric drill. The study's authors recommend that workers consider using electric instead of pneumatic drills.

Using the same robotic system to evaluate drilling with bits worn to different degrees, the second study found that sharp, carbide-tipped bits produced less dust, noise, and hand vibration than dull bits when drilling into concrete. The use of a dull bit can increase the time to drill a hole by up to 60 percent, as expected, but the study also found that a dull bit can increase noise by almost two decibels, generate about twice as much silica dust, and produce a small increase in handle vibration, so the potential exposures are even greater for worn bits because of the increased time required to drill a hole. "The team also found that the wear-related changes in the carbide-tip bit most closely associated with reduced productivity were reduced bit-tip width and rounding of the tip shoulders," NOISH reported. "Contractors and construction workers can check the condition of a bit by following these wear patterns. While a dust-controlling vacuum and hearing protection will still be needed for this work, the increase in productivity combined with the reduced exposure to dust, noise, and vibration makes a strong safety and business case for regularly replacing worn bits, according to the authors."

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