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Airborne hexavalent chromium (Cr[VI]) is a known human respiratory carcinogen and allergen. Workers in a variety of industries may be exposed to airborne hexavalent chromium, with exposures frequently occurring via inhalation and/or dermal contact. Analytical methods for the measurement of Cr(VI) compounds in workplace samples, rather than for the determination of total elemental chromium in workplace air, are often desired because exposure limit values for Cr(VI) compounds are much lower than for total Cr. For years, sampling and analytical test methods for airborne Cr(VI) have been investigated so as to provide means for occupational exposure assessment to this highly toxic species. Inter-conversion of trivalent chromium (Cr[III]) and Cr(VI) can sometimes occur during sampling and sample preparation, and efforts to minimize unwanted redox reactions involving these chromium valences have been sought. Because of differences in toxicity, there is also interest in the ability to differentiate between water-soluble and insoluble forms of Cr(VI), and procedures that provide solubility information concerning Cr(VI) compounds have been developed. This paper reviews the state of the art concerning the measurement of airborne Cr(VI) compounds in workplace aerosols and related samples.

On examining the published results of comparisons of sampling with Institute of Occupational Medicine (IOM) (Edinburgh, U.K.) samplers and 37-mm closed-face cassettes it was observed that they usually do not take into account the dust deposited on the walls of the cassettes. As the method used by the Institut National de Recherche et de Sécurité, France (INRS), to analyze metals includes the analysis of these deposits, it was decided to evaluate the differences obtained between these samplers when using this method. The essays were conducted in three different plants, and repetitive static samplings were carried out to compare 2 L/min, IOM cassettes and 1 or 2 L/min 37-mm closed-face cassettes. The airborne particles were also sampled simultaneously for granulometric analysis. Gravimetric determinations of sampled aerosol were obtained by weighing 37-mm filters and IOM cassettes, and the aerosol collected on the filters and the particles deposited on the walls were analyzed separately for both types of samplers by atomic spectrometry for metals content. The intra-sampler variability and inter-sampler ratios were then determined. Although results obtained for gravimetric analysis are comparable to those published elsewhere (ratio IOM/37-mm much higher than 1), the metal analysis revealed a close agreement between the results obtained with the three sampling methods tested when the wall deposits were taken into account. As published previously, the ratio of wall deposits to filter collected aerosol for 37-mm cassettes is variable, and it would appear to be very difficult to find an appropriate correction factor applicable when only the filter is analyzed. Were these results to be confirmed by further experiments, sampling with 37-mm closed-faced at 1 or 2 L/min or with an IOM sampler would be equivalent for all pollutants for which the analytical method allows the recovery of walls deposit.

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.

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