Task-specific noise exposure during manual concrete surface grinding in enclosed areas-influence of operation variables and dust control methods.

Noise exposure is a distinct hazard during hand-held concrete grinding activities, and its assessment is challenging because of the many variables involved. Noise dosimeters were used to examine the extent of personal noise exposure while concrete grinding was performed with a variety of grinder sizes, types, accessories, and available dust control methods. Noise monitoring was conducted in an enclosed area covering 52 task-specific grinding sessions lasting from 6 to 72 minutes. Noise levels, either in minute average noise level (Lavg, dBA) or in minute peak (dBC), during concrete grinding were significantly (P < 0.01) correlated with general ventilation (GV: on, off), dust control methods (uncontrolled, wet, Shop-Vac, HEPA, HEPA-Cyclone), grinding cup wheel (blade) sizes of 4-inch (100 mm), 5-inch (125 mm) and 6-inch (150 mm), and surface orientation (horizontal, inclined). Overall, minute Lavg during grinding was 97.0 ± 3.3 (mean ± SD), ranging from 87.9 to 113. The levels of minute Lavg during uncontrolled grinding (98.9 ± 5.2) or wet-grinding (98.5 ± 2.7) were significantly higher than those during local exhaust ventilation (LEV) grinding (96.2 ± 2.8). A 6-inch grinding cup wheel generated significantly higher noise levels (98.7 ± 2.8) than 5-inch (96.3 ± 3.2) or 4-inch (95.3 ± 3.5) cup wheels. The minute peak noise levels (dBC) during grinding was 113 ± 5.2 ranging from 104 to 153. The minute peak noise levels during uncontrolled grinding (119 ± 10.2) were significantly higher than those during wet-grinding (115 ± 4.5) and LEV-grinding (112 ± 3.4). A 6-inch grinding cup wheel generated significantly higher minute peak noise levels (115 ± 5.3) than 5-inch (112 ± 4.5) or 4-inch (111 ± 5.4) cup wheels. Assuming an 8-hour work shift, the results indicated that noise exposure levels during concrete grinding in enclosed areas exceeded the recommended permissible exposure limits and workers should be protected by engineering control methods, safe work practices, and/or personal protective devices.

Effectiveness of dust control methods for crystalline silica and respirable suspended particulate matter exposure during manual concrete surface grinding.

Concrete grinding exposes workers to unacceptable levels of crystalline silica dust, known to cause diseases such as silicosis and possibly lung cancer. This study examined the influence of major factors of exposure and effectiveness of existing dust control methods by simulating field concrete grinding in an enclosed workplace laboratory. Air was monitored during 201 concrete grinding sessions while using a variety of grinders, accessories, and existing dust control methods, including general ventilation (GV), local exhaust ventilation (LEV), and wet grinding. Task-specific geometric mean (GM) of respirable crystalline silica dust concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled-grinding, while GV was off/on, were 0.17/0.09, 0.57/0.13, 1.11/0.44, and 23.1/6.80, respectively. Silica dust concentrations (mg/m³ using 100-125 mm (4-5 inch) and 180 mm (7 inch) grinding cups were 0.53/0.22 and 2.43/0.56, respectively. GM concentrations of silica dust were significantly lower for (1) GV on (66.0%) vs. off, and (2) LEV:HEPA- (99.0%), LEV:Shop-vac- (98.1%) or wet- (94.4%) vs. uncontrolled-grinding. Task-specific GM of respirable suspended particulate matter (RSP) concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled grinding, while GV was off/on, were 1.58/0.63, 7.20/1.15, 9.52/4.13, and 152/47.8, respectively. GM concentrations of RSP using 100-125 mm and 180 mm grinding cups were 4.78/1.62 and 22.2/5.06, respectively. GM concentrations of RSP were significantly lower for (1) GV on (70.2%) vs. off, and (2) LEV:HEPA- (98.9%), LEV:Shop-vac- (96.9%) or wet- (92.6%) vs. uncontrolled grinding. Silica dust and RSP were not significantly affected by (1) orientation of grinding surfaces (vertical vs. inclined); (2) water flow rates for wet grinding; (3) length of task-specific sampling time; or, (4) among cup sizes of 100, 115 or 125 mm. No combination of factors or control methods reduced an 8-hr exposure level to below the recommended criterion of 0.025 mg/m³ for crystalline silica, requiring further refinement in engineering controls, administrative controls, or the use of respirators.

Occupational silica exposure as a risk factor for scleroderma: a meta-analysis.

OBJECTIVES: Among potential environmental risk factors for systemic sclerosis (SSc), occupational exposures have received some attention. In this meta-analysis, we examined the association between SSc and occupational exposure to silica. METHODS: We searched Medline, Toxline, BIOSIS, and Embase (1949 and November 2009) for original articles published in any language. Sixteen studies are included in the analysis, of which, 3 are cohort studies, 9 case-control and 4 are of other designs. The combined estimator of relative risk (CERR) and 95% confidence interval (CI) were calculated using fixed or random effect models. RESULTS: Significant heterogeneity was detected (I (2) = 97.2%; P < 0.01), and the CERR was 3.20 (95% CI, 1.89-5.43). The CERR for studies in females was 1.03 (95% CI, 0.74-1.44) and was 3.02 (95% CI, 1.24-7.35) for males. The CERR for case-control studies was 2.24 (95% CI, 1.65-3.31) and was 15.49 (95% CI, 4.54-52.87) for cohort studies. CONCLUSIONS: The findings suggest that silica exposure may be a significant risk factor for developing SSc and specifically in males. Further observational studies examining the role of occupational silica exposure in the context of other risk factors are needed.

Occupational noise exposures among three farm families in northwest Ohio.

A pilot project was conducted to evaluate occupational noise exposures of three families living and working on farms in Northwest Ohio. Noise exposures were measured continuously for 7 consecutive days for each participant for 1 week each during planting, growing, and harvesting seasons. The dosimeters were programmed to evaluate noise exposures using both the Occupational Safety and Health Administration (OSHA) action level and the National Institute for Occupational Safety and Health (NIOSH)/American Conference of Governmental Industrial Hygienists (ACGIH) guidelines. One family was evaluated per year and a total of nine family members (six adults and three children) participated. Adult noise exposures for on-farm activities (occupational exposures) ranged from 46.1 to 89.6 decibels on the A-weighted scale (dBA) as an 8-hour time-weighted average (8HR TWA) using the OSHA action level and from 62.6 to 92.1 dBA 8HR TWA using the NIOSH/ACGIH guidelines. Occupational noise exposures for the children ranged from 15.4 to 81.2 dBA 8HR TWA using the OSHA action level and from 42.4 to 85.5 dBA 8HR TWA using the NIOSH/ACGIH guidelines. Six of 45 exposures among the adults and none of the 11 exposures among the children exceeded the OSHA action level. In addition, 10 of 45 exposures among the adults and 1 of 11 exposures among the children exceeded the NIOSH/ACGIH guidelines. The results of this pilot project indicate noise exposures among farm families can exceed recommended levels.