TIMING OF SAMPLE COLLECTION FOR BIOLOGICAL MONITORING OF OCCUPATIONALEXPOSURE

The timing of sample collections for the biological monitoring of occu pational exposure profoundly affects the resulting data. Sampling time with respect to the day in the working week and the end of exposure i s crucial for measurements of rapidly excreted indicators of exposure. Owing to the cumulation of slowly excreted exposure indicators, timin g of sample collection with respect to the duration of employment is e ssential. The steady state is established within a week, if the exposu re indicator is excreted rapidly (with a half-life shorter than 45 h), or within months or years, if it is excreted slowly. In this study, e xposure indicators are characterized by the elimination half-life. A m onocompartmental model is used to calculate the biological levels at s teady state and the duration of occupational exposure needed to reach the apparent steady state. (C) 1997 British Occupational Hygiene Socie ty.