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A new method for estimating dermal absorption from chemical exposure. 3. Compared with steady-state methods for
A L Bunge1, R L Cleek, B E Vecchia
1Chemical Engineering and Petroleum Refining Department, Colorado School of Mines, Golden 80401, USA.
Pharmaceutical Research
|July 1, 1995
Summary
The steady-state method underestimates dermal absorption, especially for short exposures. Unsteady-state analysis is crucial for accurate dermal absorption and permeability estimations in scientific research.
Area of Science:
- Environmental chemistry
- Toxicology
- Pharmacokinetics
Background:
- Dermal absorption is a key route for chemical exposure.
- Accurate estimation of dermal absorption is vital for risk assessment.
- Traditional steady-state models may not capture transient absorption dynamics.
Purpose of the Study:
- To compare unsteady-state and steady-state methods for dermal absorption estimation.
- To analyze dermal absorption data considering varying exposure times.
- To evaluate the impact of the viable epidermis as a barrier to lipophilic chemicals.
Main Methods:
- Applied unsteady-state and steady-state models to five chemicals (chloromethane, chloroform, chlordane, 2,3,7,8-TCDD, dibenz(a,h)anthracene).
- Calculated dermal absorption from aqueous solutions for chemicals with MW 50-410 and log10Kow 0.91-6.8.
- Evaluated in vivo and in vitro permeation measurements using the new method.
Main Results:
- Steady-state methods significantly underestimated dermal absorption in all five cases.
- Permeability values were overestimated when calculated from data with exposure < 18x stratum corneum lag time.
- Unsteady-state conditions lead to inaccurate permeability calculations.
Conclusions:
- Steady-state predictions generally underestimate actual dermal absorption.
- Inclusion of unsteady-state data is essential for correct permeability calculations.
- Strategies for analyzing in vitro diffusion cell experiments and confirming steady state were provided.