Evaluation of irritancy and sensitization potential of metalworking fluid mixtures and components.

There are approximately 1.2 million workers exposed to metalworking fluids (MWF), which are used to reduce the heat and friction associated with industrial machining and grinding operations. Irritancy and sensitization potential of 9 National Toxicology Program (NTP) nominated MWFs (TRIM 229, TRIM VX, TRIM SC210, CIMTECH 310, CIMPERIAL 1070, CIMSTAR 3800, SYNTILO 1023, SUPEREDGE 6768, and CLEAREDGE 6584) were examined in a combined local lymph node assay (LLNA). BALB/c mice were dermally exposed to each MWF at concentrations up to 50%. Significant irritation was observed after dermal exposure to all MWFs except CIMTECH 310 and SYNTILO 1023. Of the 9 MWFs, 6 induced greater than a 3-fold increase in lymphocyte proliferation and 7 tested positive in the irritancy assay. TRIM VX yielded the lowest EC3 value (6.9%) with respect to lymphocyte proliferation. Chemical components of TRIM VX identified using HPLC were screened for sensitization potential using structural activity relationship (SAR) modeling and the LLNA. TOPKAT predicted triethanolamine (TEA) as a sensitizer while Derek for Windows predicted only 4-chloro-3-methylphenol (CMP) to be positive for sensitization. When tested in the LLNA only CMP (EC3 = 11.6%) and oleic acid (OA) (EC3 = 29.7%) were identified as sensitizers. Exposure to all tested TRIM VX components resulted in statistically significant irritation. An additive proliferative response was observed when mixtures of the two identified sensitizing TRIM VX components, OA and CMP, were tested in the LLNA. This is one explanation of why the EC3 value of TRIM VX, with respect to lymphocyte proliferation, is lower than those assigned to its sensitizing components.

Application of solid-phase microextraction to in vitro skin permeation experiments: example using diethyl phthalate.

The application of automated solid-phase microextraction (SPME) as a sample preparation technique for in vitro studies of skin permeation is described, using diethyl phthalate (DEP) as an example. In vitro diffusion cell experiments and skin-vehicle partition coefficient determinations require quantitative analysis of low-level analytes in aqueous samples. SPME is an ideal candidate for sample preparation for subsequent gas chromatographic analysis, offering numerous advantages over other methods. SPME conditions were optimized and the automated method was found to exhibit adequate sensitivity and good precision (relative standard deviation=3%). Abdominal skin (dermatomed at 350 microm) from male hairless guinea pigs (n=6) was used to measure DEP skin permeation parameters. In vitro methods were employed to determine permeability coefficient (k(p)), time lag (tau) and skin-buffer partition coefficient (K(SB)) for 2 mM DEP in HEPES buffered Hanks Balanced Salt Solution. Measurements (mean+/-standard deviations) are: k(p), 0.021+/-0.012 cm/h; tau, 0.67+/-0.18 h; K(SB), 4.74+/-0.68. The skin may be a significant route for the uptake of DEP.