GRINDING DUSTS OF ALLOYED STEEL AND HARD METAL

A knowledge of the properties of airborne dusts containing compounds of Cr, Ni and Co is valuable when estimating biological monitoring methods and health risks. In this study chemical, physical and magnetic properties of alloyed steel and hard metal grinding dusts have been examined. Twenty-one stainless steel grinders from one workshop were selected for measurements of magnetic lung contamination and urinary chromium and nickel. The dust samples were analyzed for total elemental composition, water solubility and acid solubility. Scanning electron microscopy and energy dispersive X-ray analysis were used for characterizing the dust particles. The highest concentration of total chromium (7–18%) was found in the dust from high-alloyed steel grinding. The concentration of total nickel varied between 1.5 and 6% in different types of alloyed steel grinding dusts. Dust particles seem to have the same metallic structure as the ground stainless steel piece. Concentrations of tungsten and cobalt in hard metal grinding dusts were up to 20 and 25%, respectively. An enrichment of cobalt in the airborne dust compared with the base material was also observed. Oxidation of alloyed elements in alloyed steel grinding dusts is slight, therefore water soluble chromium and nickel compounds do not exist. All the grinding dusts studied showed high magnetic moments, sufficiently for the in vivo measurement of lung retained dust. The average lung retention of metallic particles among stainless steel grinders was 200 mg. Urinary chromium and nickel values for all stainless steel grinders were below the detection limit.