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Bioavailability of soil-bound TCDD: dermal bioavailability in the rat
H Shu1, P Teitelbaum, A S Webb
1Syntex Corporation, Palo Alto, California 94304.
Summary
Dermal absorption of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) in rats was about 1% after 24-hour soil contact. Rat skin permeability to TCDD is higher than human skin, meaning this 1% value may overestimate human exposure.
Area of Science:
- Environmental Toxicology
- Dermal Absorption Studies
- Chemical Contaminant Analysis
Background:
- 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant found at numerous sites.
- Regulatory agencies require data on TCDD dermal absorption from soil to assess human exposure risks.
Purpose of the Study:
- To quantify the dermal absorption of TCDD bound to soil in rats.
- To investigate factors influencing TCDD dermal absorption, including dose, contact time, co-contaminants, and soil type.
Main Methods:
- Rats were exposed to TCDD-contaminated soil for varying durations (4 and 24 hours).
- Soil contamination included TCDD alone or with crankcase oil.
- Environmentally and laboratory-prepared contaminated soils were used.
Main Results:
- Dermal penetration after 4 hours was 60% of that after 24 hours (P <= 0.05).
- Approximately 1% of the administered TCDD dose was absorbed dermally after 24 hours of soil contact.
- TCDD concentration, crankcase oil, and soil origin did not significantly affect dermal uptake.
Conclusions:
- Rat skin exhibits significant dermal absorption of soil-bound TCDD.
- The 1% dermal uptake value in rats may overestimate human exposure due to species differences in skin permeability.
- Further research is needed to accurately extrapolate rat dermal absorption data to human risk assessment.