The In Vitro Permeability Coefficient and Short-Term Absorption Rates for Vinyl Toluene Using Human Cadaver Skin Mounted in a Static Diffusion Cell Model

Abstract

Vinyl toluene is one of several methylstyrene monomers that provide improved performance in resins for specialty paints, hydrocarbon resins for adhesives, specialty polymers, and unsaturated polyester resins. The purpose of this study was to determine a permeability coefficient (Kp) and short-term absorption rate for vinyl toluene using human cadaver skin mounted in an in vitro static diffusion cell model with an exposure area of 0.64 cm². For the Kp determination, vinyl toluene was applied at a rate of 100 μL/cm² to 6 skin replicates representing 4 human subjects. Serial receptor fluid samples were collected at 1, 2, 4, 8, 12, 24, 36, and 48 h postapplication and analyzed for vinyl toluene by HPLC-UV. Based on the slope at steady-state (203.3 μg cm⁻² h⁻¹ ± 120.0 μg cm⁻² h⁻¹) and the concentration of the applied dose of vinyl toluene, taken as its density (894,600 μg/cm³), the Kp was calculated to be 2.27 × 10⁻⁴ cm/h (±1.34 × 10⁻⁴ cm/h). For the short-term absorption experiments, 12 skin replicates representing 3 human subjects were employed. Following 10- and 60-min exposures to a finite dose of vinyl toluene (10 μL/cm²), the respective short-term absorption rates were calculated to be 66.0 (±29.9) and 104.2 (±63.0) μg cm⁻² h⁻¹. These data provide industrial hygienists and safety personnel values to estimate the amount of vinyl toluene that may be absorbed via the dermal exposure route, given a variety of exposure scenarios, and the time it takes (skin absorption time) to reach a body burden equal to the Occupational Safety and Health Administrative permissible exposure level (OSHA PEL) or ACGIH TLV.

Key Words: :

• Electrical impedance (EI)
• In vitro dermal absorption
• Permeability coefficient (Kp)
• Short-term absorption rate
• Skin absorption time
• Vinyl toluene

Notes

EC. (2002). European Commission guidance document on dermal absorption. Sanco/222/2000 rev 6

NIOSH. (1983). National Occupational Exposure Survey (NOES)

OECD. (2002a). OECD Guideline for the testing of chemicals. Draft new guideline 428: Skin absorption: in vitro method

OECD. (2002b). OECD Draft guidance document for the conduct of skin absorption studies. OECD Environmental Health and Safety Publication Series on Testing and Assessment No. 28

USEPA (1992). Dermal exposure assessment: principles and applications, interim report, EPA/600/8-91/011B, pp.8–8–8–13