Owing to fluctuations in pollutant concentration over time, measurement and averaging time has a key effect on the value obtained. Long-term concentrations and long-term exposure data cannot therefore be applied directly 1:1 to shift durations. For the necessary conversion of mean concentration data from long-term studies to a shift limit value, this article describes how to derive a suitable factor. The factor is based on the assumption of a log-normal distribution of measured values and on their empirically estimated Geometrical standard deviations. Conversion factors between 2.5 and 7 were obtained for a 97.5 percentile. If there is no knowledge of the measured value distribution, a factor of at least 2 to 3 can be assumed with a conservative presupposition of a 97.5 percentile. These considerations were incorporated in a MAK Commission document on this subject.
Authors: Bochmann, F.; Morfeld, P. ;Full Source: Gefahrstoffe-Reinhaltung der Luft 2011, 71(10), 419-424 (Germany) ;