PREPARATION OF FILTERS LOADED WITH WELDING DUST - A HOMOGENEITY AND STABILITY STUDY OF HEXAVALENT CHROMIUM

One hundred filters were loaded with welding fume dust, collected in industrial working conditions, and the homogeneity and the stability of the materials with regard to Cr(VI) were verified. The filters were loaded, using a Sputnic air sampling unit containing 100 binderfree glass fibre filters. The filter load was determined by weighing before and after exposure. The mean amount of dust, charged on 98 filters amounted to 2.565 mg/filter (C.V. = 3.4%). The load of hexavalent chromium on the filters corresponds to loads usually found on occupationally charged filters (approx. Cr(VI) 100 mu g/filter). The homogeneity was verified by analyzing 16 filters selected from the four rings of the Sputnic air sampler. The results proved the homogeneity of Cr(VI) on the batch of filters. Filters were stored at 25 degrees C and -20 degrees C and the stability of Cr(VI) and total soluble Cr was verified after 1, 4 and 13 week(s). The results showed no significant difference between the filters stored at 25 degrees C and -20 degrees C. In all cases no Cr(III) could be detected (below LOD) with the analytical procedure used, and no significant difference was found between the amounts of Cr(VI) and total Cr determined. Normalization of the amount of hexavalent chromium measurements according to the dust Load substantially improves the analytical data.