Characterizing and Comparing Emissions of Dust, Respirable Crystalline Silica, and Volatile Organic Compounds from Natural and Artificial Stones.

The frequency of cases of accelerated silicosis associated with exposure to dust from processing artificial stones is rapidly increasing globally. Artificial stones are increasingly popular materials, commonly used to fabricate kitchen and bathroom worktops. Artificial stones can contain very high levels of crystalline silica, hence cutting and polishing them without adequate exposure controls represents a significant health risk. The aim of this research was to determine any differences in the emission profiles of dust generated from artificial and natural stones when cutting and polishing. For artificial stones containing resins, the nature of the volatile organic compounds (VOCs) emitted during processing was also investigated. A selection of stones (two natural, two artificial containing resin, and one artificial sintered) were cut and polished inside a large dust tunnel to characterize the emissions produced. The inhalable, thoracic, and respirable mass concentrations of emissions were measured gravimetrically and the amount of crystalline silica in different size fractions was determined by X-ray diffraction. Emissions were viewed using scanning electron microscopy and the particle size distribution was measured using a wide range aerosol spectrometer. VOCs emitted when cutting resin-artificial stones were also sampled. The mass of dust emitted when cutting stones was higher than that emitted when polishing. For each process, the mass of dust generated was similar whether the stone was artificial or natural. The percentage of crystalline silica in bulk stone is likely to be a reasonable, or conservative, estimate of that in stone dust generated by cutting or polishing. Larger particles were produced when cutting compared with when polishing. For each process, normalized particle size distributions were similar whether the stone was artificial or natural. VOCs were released when cutting resin-artificial stones. The higher the level of silica in the bulk material, the higher the level of silica in any dust emissions produced when processing the stone. When working with new stones containing higher levels of silica, existing control measures may need to be adapted and improved in order to achieve adequate control.

The Measurement of Wood in Construction Dust Samples: A Furnace Based Thermal Gravimetric Approach.

A furnace-based thermal gravimetric method was developed to measure wood in inhalable construction dust. The application of this method showed that reliance on the inhalable concentrations alone may substantially overestimate carpenters' exposures to wood dust at construction worksites. Test samples were prepared by collecting aerosols of gypsum, calcite, quartz, concrete, and wood dust onto quartz fibre filters using the Button inhalable sampler. The average difference between the measured and loaded mass of wood is 2% over the whole analytical range. Ninety percent of thermogravimetric measurements on all test samples (n = 35) were 13% or less. The limit of detection was measured as 0.065 mg. The thermal gravimetric method was applied to samples collected from four new build construction sites and one shop fitting worksite. The workplace inhalable wood dust results ranged from 15% to 104% of the total inhalable dust values. In addition, an x-ray diffraction (XRD) Rietveld method was applied as a complimentary approach to explain the composition of the remaining inhalable dust. Most combined thermal gravimetric and XRD measurements were within 10% of the total inhalable dust mass values, determined gravimetrically. Ninety-five percent were within 26%. The median proportion of mineral dust containing gypsum, calcite, quartz, dolomite, or rutile was 30%. The proportion of mineral dust on individual filters varied considerably.