Silica Measurement with High Flow Rate Respirable Size Selective Samplers: A Field Study.

High and low flow rate respirable size selective samplers including the CIP10-R (10 l min(-1)), FSP10 (11.2 l min(-1)), GK2.69 (4.4 l min(-1)), 10-mm nylon (1.7 l min(-1)), and Higgins-Dewell type (2.2 l min(-1)) were compared via side-by-side sampling in workplaces for respirable crystalline silica measurement. Sampling was conducted at eight different occupational sites in the USA and five different stonemasonry sites in Ireland. A total of 536 (268 pairs) personal samples and 55 area samples were collected. Gravimetric analysis was used to determine respirable dust mass and X-ray diffraction analysis was used to determine quartz mass. Ratios of respirable dust mass concentration, quartz mass concentration, respirable dust mass, and quartz mass from high and low flow rate samplers were compared. In general, samplers did not show significant differences greater than 30% in respirable dust mass concentration and quartz mass concentration when outliers (ratio <0.3 or >3.0) were removed from the analysis. The frequency of samples above the limit of detection and limit of quantification of quartz was significantly higher for the CIP10-R and FSP10 samplers compared to low flow rate samplers, while the GK2.69 cyclone did not show significant difference from low flow rate samplers. High flow rate samplers collected significantly more respirable dust and quartz than low flow rate samplers as expected indicating that utilizing high flow rate samplers might improve precision in quartz measurement. Although the samplers did not show significant differences in respirable dust and quartz concentrations, other practical attributes might make them more or less suitable for personal sampling.

An evaluation of on-tool shrouds for controlling respirable crystalline silica in restoration stone work.

OBJECTIVES: The task of grinding sandstone with a 5-inch angle grinder is a major source of exposure to respirable crystalline silica (RCS), known to cause diseases such as silicosis and lung cancer among workers who work with these materials. A shroud may be a suitable engineering control for this task. The objectives of this study were to evaluate the effectiveness of four commercially available shrouds at reducing respirable dust and RCS levels during the task of grinding sandstone using tools and accessories typical of restoration stone work. METHODS: The task of grinding sandstone with a 5-inch angle grinder, equipped with different grinding wheels, was carried out over three trials at a restoration stone masonry site. Photometric and RCS data were collected when a 5-inch grinder, equipped with different grinding wheels, was used to grind sandstone with and without a shroud. A total of 24 short duration samples were collected for each no shroud and with shroud combination. Worker feedback on the practicalities of each shroud evaluated was also collected. RESULTS: Respirable dust concentrations and RCS were both significantly lower (P < 0.001) when the grinders were equipped with a shroud compared with grinders without a shroud. Total geometric mean (GM) photometric respirable dust levels measured when grinding with a shroud were 0.5 mg m(-3), a reduction of 92% compared to grinding without a shroud (7.1 mg m(-3)). The overall GM RCS concentrations were reduced by the use of a shroud by 99%. GM photometric exposure levels were highest when using the Hilti 5-inch diamond grinding cup and Diamond turbo cup and lowest when using the Corundum grinding point. CONCLUSIONS: Concentrations of respirable dust and RCS can be significantly reduced by using commercially available shrouds while grinding sandstone with a 5-inch angle grinder in restoration stonework. The short-term photometric respirable dust and RCS measurements collected with and without a shroud indicate that dust and RCS concentrations are reduced by between 90 and 99%. Supplemental exposure controls such as respiratory protective equipment would be required to reduce worker 8-h time-weighted average RCS exposure to below the Scientific Committee on Occupational Exposure Limits recommended occupational exposure limit value of 0.05 mg m(-3) and the American Conference of Governmental Industrial Hygienists threshold limit value of 0.025 mg m(-3).

Determinants of respirable crystalline silica exposure among stoneworkers involved in stone restoration work.

OBJECTIVES: Crystalline silica occurs as a significant component of many traditional materials used in restoration stonework, and stoneworkers who work with these materials are potentially exposed to stone dust containing respirable crystalline silica (RCS). Exposure to RCS can result in the development of a range of adverse health effects, including silicosis and lung cancer. An understanding of the determinants of RCS exposure is important for selecting appropriate exposure controls and in preventing occupational diseases. The objectives of this study were to quantify the RCS exposure of stoneworkers involved in the restoration and maintenance of heritage properties and to identify the main determinants of RCS exposure among this occupational group. METHODS: An exposure assessment was carried out over a 3-year period amongst a group of stonemasons and stone cutters involved in the restoration and maintenance of heritage buildings in Ireland. Personal air samples (n = 103) with corresponding contextual information were collected. Exposure data were analysed using mixed-effects modelling to investigate determinants of RCS exposure and their contribution to the individual's mean exposure. Between-depot, between-worker, and within-worker variance components were also investigated. RESULTS: The geometric mean (GM) RCS exposure concentrations for all tasks measured ranged from <0.02 to 0.70mg m(-3). GM RCS exposure concentrations for work involving limestone and lime mortar were <0.02-0.01mg m(-3), tasks involving granite were 0.01-0.06mg m(-3), and tasks involving sandstone were <0.02-0.70mg m(-3). Sixty-seven percent of the 8-h time-weighted average (TWA) exposure measurements for tasks involving sandstone exceeded the Scientific Committee on Occupational Exposure Limits recommended occupational exposure limit value of 0.05mg m(-3). Highest RCS exposure values were recorded for the tasks of grinding (GM = 0.70mg m(-3)) and cutting (GM = 0.70mg m(-3)) sandstone. In the mixed-effects analyses, task was found to be significantly associated with RCS exposure, with the tasks of grinding and cutting resulting in average exposures of between 32 and 70 times the exposures recorded for the task of stone decorating. The between-depot, between-worker, and within-worker variance components were reduced by 46, 89, and 49%, respectively, after including task in the mixed effects model. CONCLUSIONS: Restoration stoneworkers are regularly overexposed (compared with 0.1 and 0.05mg m(-3) 8-h TWA) to RCS dust when working with sandstone. The results indicate that the tasks of cutting and grinding sandstone are predictors of increased exposure to RCS dust. In order to decrease exposure to RCS, efforts should be focused on developing and implementing interventions which focus on these high-risk tasks.

Performance of High-Flow-Rate Samplers for Respirable Crystalline Silica Measurement Under Field Conditions: Preliminary Study.

Restoration stone work regularly involves work with high-silica-content materials (e.g., sandstone), but low-silica-content materials (<2 % quartz) such as limestone and lime mortar are also used. A combination of short sample duration and low silica content makes the quantification of worker exposure to respirable crystalline silica (RCS) difficult. This problem will be further compounded by the introduction of lower occupational exposure standards for RCS. The objective of this work was to determine whether higher-flow samplers might be an effective tool in characterizing lower RCS concentrations. A short study was performed to evaluate the performance of three high-flow samplers (FSP10, CIP10-R, and GK2.69) using side-by-side sampling with low-flow samplers (SIMPEDS and 10-mm nylon cyclones) for RCS exposure measurement at a restoration stonemasonry field site. A total of 19 side-by-side sample replicates for each high-flow and low-flow sampler pair were collected from work tasks involving limestone and sandstone. RESULTS: Most of the RCS (quartz) masses collected with the high-flow-rate samplers were above the limit of detection (62 % to 84 %) relative to the low-flow-rate samplers (58 % to 78 %). The average of the respirable mass concentration ratios for CIP10-R/SIMPEDS, GK2.69/10-mm nylon, FSP10/SIMPEDS, and FSP10/10-mm nylon pairs and the range of the quartz concentration ratios for the CIP10-R/SIMPEDS, CIP10-R/10-mm nylon, GK2.69/10-mm nylon, FSP10/SIMPEDS, and FSP10/10-mm nylon pairs included unity with an average close to unity, indicating no likely difference between the reported values for each sampler. Workers reported problems related to the weight of the sampling pumps for the high-flow-rate samplers. Respirable mass concentration data suggest that the high-flow-rate samplers evaluated would be appropriate for sampling respirable dust concentrations during restoration stone work. Results from the comparison of average quartz concentration ratios between high-and low-flow samplers suggest that the higher mass collected by the high-flow-rate samplers did not interfere with the quartz measurement. A sig-nificant portion of the data collected with the high-flow-rate samplers (>82 %) were greater than the limit of detection, which indicates that these samplers are suitable for quantifying exposures, even with low-quartz materials.