The exposure assessment allows the biological monitoring of workers by assessing their exposure to substances from
the working environment, for example, a personal sampling for the toluene concentration, and an assessment of the
environmental concentrations of the solvents that can enter the body via the respiratory tract and skin. The assessment of
chemicals can be based on parent compounds or metabolites, such as from blood and urine. The assessment of chemicals in urine is preferred rather than a blood test because it is a noninvasive method. The relationship between the level of toluene in urine and the concentration of toluene in the working environment as found by using the personal passive badge has already been demonstrated.