Because most masonry building materials contain quartz and because these materials are subjected to a variety of treatments during the building process, quartz is encountered everywhere in building operations. The level of exposure to respirable quartz has been measured for some highly exposed groups of employees. At 30 construction sites personal air sampling (PAS) measurements of respirable dust and quartz have been performed and 171 samples have been taken. Both respirable dust and quartz

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... els were high. Respirable quartz exposures of more than ten times the Dutch limit value of 0.075 mg/m 3 TWA were common, but exposures up to 200 times the Dutch limit value were also found. The measurements were task oriented. By statistical analysis the contribution of the different determinants to the total exposure has been identified. With this approach, directions for an effective control measures programme can be given.