Timing of sample collection for biological monitoring of occupational exposure.

The timing of sample collections for the biological monitoring of occupational exposure profoundly affects the resulting data. Sampling time with respect to the day in the working week and the end of exposure is crucial for measurements of rapidly excreted indicators of exposure. Owing to the cumulation of slowly excreted exposure indicators, timing of sample collection with respect to the duration of employment is essential.

Exposure limits for unconventional shifts: toxicokinetic and toxicodynamic considerations.

Adjustment factors (AF) for inhalation exposure to chemical agents during unconventional work schedules were derived on toxicokinetic bases. AFs depend on the half-life of the agent and on the work schedule. Because they are grossly affected by cumulation, AFs were calculated for steady-state conditions.

Extrapolation of physiological parameters for physiologically based simulation models.

Masses of organs and fluids, pulmonary ventilation and cardiac output and its distribution are the basic input data used in physiologically based pharmacokinetic models. Since these parameters are rarely measured in pharmacokinetic studies, the values found in reference books or extrapolated to meet the specific exposure conditions are used in the models. In this review of the extrapolation of pertinent physiological parameters, power equations for scaling across mammals, adjustments to body build (lean body mass) and physical activity of humans and their significance for risk assessment of human exposure to solvents using animal data are assessed.

Relevance of occupational skin exposure.

Dermal exposure gains in significance by the same token as permissible occupational inhalation exposures are lowered. The contribution of dermal absorption to the total dose absorbed during occupational exposure is apparent when dermal and pulmonary uptake rates are compared. Development of an experimental data base for evaluation and control of dermal exposure is hindered by: lack of suitable methods for measurement of dermal absorption in humans; interspecies differences in skin permeability; regional differences in absorption rates due to non-homogeneity of skin composition and perfusion rates over the body; possible skin damage induced by the chemical or dispersant; and exposure conditions in the workplace.