Proposal to adapt the Workplace Analysis Scheme for Proficiency (WASP) programme to fibre counting tests.

Three methods of classifying laboratories during fibre counting proficiency tests were compared. The first two are those used in France (classification according to the mean and coefficient of variation of the results) and in Great Britain (classification according to the proportion of normalized results situated within predefined limits). The third is a variation of the Workplace Analysis Scheme for Proficiency (WASP) programme adapted to fibre counting tests. In the latter case, the laboratory classification is based on comparing the variance characterizing the dispersion of the results of a laboratory with a reference variance, which is considered as the variance of experienced analysts or laboratories. This mode of processing has the advantage of allowing the comparison of magnitudes. For example, the variance of the reference value can be compared with the reference variance. The same applies if a proficiency test is organized on the basis of replicas distributed to different analysts, the variability of these replicas can be compared with the reference variance. It emerged that the modified WASP method produces results close to those obtained by the other two methods. Moreover, the selectivity of the three methods is evaluated.

Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration.

The use of direct-reading instruments to measure the airborne fibre number concentration is on the increase. The response of two of these instruments (FM-7400 and Fibrecheck FC-2) was compared with the conventional method of sampling on filters and counting by phase contrast microscopy. Four types of fibres were studied at different concentrations and relative humidity levels. The FM-7400 can be calibrated by the manufacturer for two different levels of sensitivity (standard and high). For the tests where it was set to the sensitivity level with which it had been calibrated, the ratio of the concentration measured by the instrument to the concentration obtained by the conventional method varied in the range 0.5-1 for the different types of fibres studied (chrysotile, glass wool and ceramic fibres). The Fibrecheck FC-2 is a much less versatile instrument. On the basis of a calibration allowing correct detection of asbestos fibres, it greatly overestimated the concentration of man-made mineral fibres. In its normal calibration state a fine chrysotile aerosol was poorly detected. For man-made mineral fibres, the response was highly dependent on the nature of the fibres. These instruments require calibration with the type of fibres to be studied. Unfortunately, this operation is not always accessible to the user and may require the services of a specialized laboratory, as the manufacturer is not always in a position to carry this out.

Comparison by X-ray diffraction and infrared spectroscopy of two samples of alpha quartz with the NIST SRM 1878a alpha quartz.

The aim of this study was to compare the X-ray diffraction and infrared spectrophotometric patterns of two samples of alpha quartz (QUIN1 and QUIN2) with that of NIST SRM 1878a alpha quartz certified 100% crystalline. As it is known that the intensity diffracted and the absorbance per mass unit for a given type of alpha quartz depend on its particle size, this factor was taken into account. To do this, different types of alpha quartz were sampled on filters using a Dorr-Oliver cyclone to select particle size. Variation in the flow rate of the cyclone in the range 1.2-2.8 l/min allowed the volume median diameter of the sampled particles to be varied. For the four strongest diffraction lines it was observed that the intensity per mass unit increased with the volume median diameter of the particles. For infrared spectrophotometry for analytical band wavelengths close to 12.5 micro m, it was observed that the absorbance per mass unit decreased as particle size increased. The opposite effect was noted for analytical band wavelengths >14.4 micro m. Compared with SRM 1878a alpha quartz, certified 100% crystalline, the purity of QUIN1 alpha quartz was 93.1% (confidence interval 92.4-93.8%) when measured by X-ray diffraction and 91.5% (confidence interval 90.1-92.9%) when measured by infrared spectrophotometry. In the case of QUIN2 alpha quartz the purity was globally lower.

Performance of asbestos fibre counting laboratories by transmission electron microscopy.

In France, the owners of buildings have been obliged since February 1996 to ascertain whether asbestos has been incorporated into surfacing materials, insulation products or false ceilings. In certain circumstances, there is also a requirement to measure the airborne asbestos fibre concentration. Three years (1996-1998) of asbestos fibre count reporting are evaluated for the proficiency testing scheme organized in France to evaluate the performance of laboratories using an indirect-transfer transmission electron microscopy procedure to measure the airborne asbestos fibre concentration. Each year eight filters are distributed to each participating laboratory. These filters are obtained by filtering a suspension containing chrysotile or amphibole fibres. In 1996, 36% of the laboratories were rated 1 (the best performers; i.e. those providing counts close to the reference value). Performance improved appreciably in the last round where 85% of the laboratories were rated 1.

Phosphine sampling and analysis using silver nitrate impregnated filters.

In the field of industrial hygiene, besides the necessity of monitoring phosphine with direct reading apparatus to prevent accidents, there is a need for a method of sampling and analysing phosphine to control workers' exposure. The use of filters impregnated with silver nitrate to collect arsine, phosphine and stibine in workplace air has been described in the literature. Having previously chosen this type of filter to collect arsine, we studied its characteristics for phosphine capture. A filter impregnated with sodium carbonate was used both as a prefilter to collect the particles and to trap arsenic trioxide. After dissolving the silver compounds in nitric acid, ICP emission spectrometry was used to carry out the analysis. This article describes the comparative sampling we performed in a microelectronic laboratory and in a fumigation chamber (130 samples) to determine the concentration of AgNO3 impregnation solution to be used, the detection limit of the method and the retention capacity of the impregnated filters. Interference with other gases reacting with silver nitrate was studied and the storage time for sampled filters and analysis solutions was checked. The detection limit of the adopted method is better than 1 microg per filter, and the retention capacity exceeds 300 microg per filter. The problem of how to sample phosphine when H2S, NH3, or HCl is present has been solved, but the problem of sampling phosphine in atmospheres where acetylene evolves remains. Sampled filters and filter solutions are stable for more than three months at ambient temperature.

Estimation of the percutaneous absorption of styrene in an industrial situation.

OBJECTIVE: This field study was designed to compare the level of styrene absorbed percutaneously with that absorbed by inhalation in a real situation in the fiberglass-reinforced polyester industry. METHODS: The study protocol consisted of comparisons of the patterns of urinary excretion of styrene metabolites by four groups of workers, all of whom performed the same task at the same time in the same workshop but wore the following different protective equipment: total protection with an insulating suit and mask, respiratory equipment only, percutaneous protection only, and no protection. RESULTS: The urinary excretion level of the group with total protection did not significantly differ from that of the group with respiratory protection only. CONCLUSIONS: Precutaneous absorption is not a particularly important pathway for styrene absorption during stratification work in the polyester industry. Completely insulating personal protective equipment provides no greater level of protection than does a respirator at positive pressure alone.