Evaluation of silica exposures during micro trenching
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Evaluation of silica exposures during micro trenching

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    "Management from a communications company requested a health hazard evaluation concerning employee exposure to respirable crystalline silica during micro trenching activities (process of cutting the roadway to install communication cable). During a given workday, employees performed tasks that included cutting the micro trench, installing the cable, emptying the vacuum truck, filling the micro trench, and loading the dumpster. Over a three-day period, we observed work processes and work practices, collected air samples for respirable crystalline silica and respirable dust, collected bulk samples of the material being cut to determine its silica content, and measured the air velocity in the vacuum hose. We found low concentrations of respirable dust in the air; respirable crystalline silica was not detected. The vacuum truck appeared to control exposures. Emptying the vacuum and loading the dumpster produced the most dust. We found between 5.5% and 26% quartz in the bulk samples. Employees were not wearing their respirators correctly, and appeared to be unsure about proper donning and doffing techniques. Some employees had facial hair and did not recall being fit tested. We recommended the company explore other methods for loading the dumpster and cleaning the vacuum filter because these tasks caused the most dust, and potentially, the greatest risk of exposures. We made a number of recommendations on ways to improve the company respiratory protection program. We also recommended the company perform periodic noise monitoring to determine which job tasks require hearing protection as there appeared to be excessive noise generated when the saw and vacuum when both were operating together." - NIOSHTIC-2

    NIOSH no. 20056742

    Recommended citation: NIOSH [2019]. Evaluation of silica exposures during micro trenching. By Grant MP, Hammond DR. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Health Hazard Evaluation Report 2019-0020-3353, https://www.cdc.gov/niosh/hhe/reports/pdfs/2019-0020-3353.pdf.

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