Assessment of cut-off saw control methods for respirable particulate and crystalline silica during highway construction applications

Beauregard Middaugh, Purdue University

Abstract

The purpose of the study was to investigate the dust reduction capabilities of currently available wet suppression and local exhaust ventilation (LEV) methods for gas-powered cut-off saws during the sawing of concrete curb on highway construction worksites. Dust control efficiency (e.g. concrete displacement rate) and weather conditions (e.g. wind) were also monitored to determine their effects on dust reduction. Personal filter cassette sampling revealed a median percent reduction in respirable (RSP) dust concentrations of 87.7 percent for the wet sawing method (WSM) and 87.0 percent for the LEV sawing method (LSM) compared to the traditional dry sawing method (DSM). A statistically significant difference (p<0.001) was seen between both the WSM and LSM compared to the DSM; however, no significant difference (p=0.118) was seen between the WSM and LSM. Based on estimated values of percent quartz, the RSP quartz reduction was approximately 84.4 percent for the WSM and 77.1 for the LSM. If workers are only exposed to RSP silica during the normal two hour cutting duration, the WSM and LSM would reduce RSP silica concentrations below the National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL). Concrete displacement rates revealed a 63.1 percent reduction in productivity for the WSM and 40.0 percent reduction in productivity for the LSM compared to the DSM. After adjusting the traditional two hour cutting time for reductions in productivity, exposure was shown to increase by 33 percent for the WSM and 29 percent for the LSM. Although both the WSM and LSM were still below the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL), they were no longer below the NIOSH REL after this adjustment. A combination of wind speed and wind direction was also shown to be a significant predictor (p=0.02) of exposure during the DSM. Video exposure monitoring revealed the WSM was more consistent in reducing peak RSP dust concentrations, but overall reductions were still similar between the WSM and LSM. Based on these findings, standardized methods of quantifying dust control effectiveness should be implemented by manufacturers to ensure proper use and appropriate comparisons between engineering controls.

Degree

M.S.

Advisors

Hubbard, Purdue University.

Subject Area

Occupational safety

COinS