Biological monitoring by determining toluene concentrations
in blood or expired air has been recommended.'
20 Samples taken during or immediately
after termination of exposure only reflect the most
recent exposure, however, and not the average
exposure during the working day. For samples taken
after the end of exposure the sampling time is critical
due to the fast decline of the toluene concentration in
blood.'4 Blood sampled Monday morning after the
exposure reflects the exposure during the preceding
week.33 At low exposures, however, it is difficult to
analyse the blood concentrations of toluene.