CONVERSION OF LONG-TERM LIMIT VALUES INTO SHIFT-RELATED LIMIT VALUES FOR SUBSTANCES WITH A SLOW EFFECT AS EG RESPIRABLE QUARTZ DUST

In limit value (MAK-value) setting, long-term limit values are assigne d to general dust exposure as well as to exposure to respirable quartz dust and quartziferous respirable dust because of the slow effect the se agents have. Therefore, the averaging time for the assessment perio d was defined as one year or as five years for the documentation of in dividual exposure to respirable quartz dust. For the conversion of lon gterm limit values into shift-related limit values a conversion factor K-AM is suggested. For determining a conversion factor K-AM it is nec essary 1. to have a mathematical and statistical derivation and 2. to know the geometrical standard deviation of the distribution of the mea surement values considered for calculating the long-term mean. The geo metrical standard deviation can be estimated for industrial branches, for professional activities or more generally. It could be shown that the geometrical standard deviation varies between 2.0 and 4.9 dependin g on the branch of industry or professional activity. From this, conve rsion factors between K-AM = 2.5 and K-AM = 7.0 can be derived. By con vention, a general conversion factor of 2.0 and a geometrical standard deviation of 2.7 could be deemed safe estimations with a view to sett ing limit values.