For years, methods have been available for the predictive identification of chemicals that possess the intrinsic potential to cause skin sensitization. However, many have proven less suitable for the determination of relative sensitizing potency. In this respect, the local lymph node assay (LLNA) has been shown to have a number of important advantages. Through interpolation of LLNA dose-response data, the concentration of a chemical required to produce a threshold positive response (a 3-fold increase in activity compared with concurrent vehicle controls, the EC3 value) can be measured. The robustness of this parameter has been demonstrated rigorously in terms of inter- and intralaboratory reproducibility. Additionally, the relationship between potency estimates from the LLNA and an appreciation of human potency based on clinical experience has been reported previously. In the present investigations, we have sought to consolidate further our understanding of the association between EC3 values and human skin-sensitization potency by undertaking a thorough and extensive analysis of existing human predictive assays, particularly where dose-response information is available, from historical human repeated insult patch tests (HRIPTs). From these human data, information on the approximate threshold for the induction of skin sensitization in the HRIPT was determined for 26 skin-sensitizing chemicals. These data were then compared with LLNA-derived EC3 values. The results from each assay, expressed as dose per unit area (microg/cm(2)), revealed a clear linear relationship between the 2 values, thereby substantiating further the utility of LLNA EC3 values for prediction of the relative human sensitizing potency of newly identified skin sensitizers.

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Access to reliable exposure data is essential for the evaluation of the toxicological safety of ingredients in cosmetic products. This study complements the data set obtained previously (Part 1) and published in 2007 by the European cosmetic industry acting within COLIPA. It provides, in distribution form, exposure data on daily quantities of five cosmetic product types: hair styling, hand cream, liquid foundation, mouthwash and shower gel. In total 80,000 households and 14,413 individual consumers in five European countries provided information using their own products. The raw data were analysed using Monte Carlo simulation and a European Statistical Population Model of exposure was constructed. A significant finding was an inverse correlation between the frequency of product use and the quantity used per application recorded for mouthwash and shower gel. The combined results of Part 1 (7 product types) and Part 2 (5 products) reported here, bring up to date and largely confirm the current exposure parameters concerning some 95% of the estimated daily exposure to cosmetics use in the EU. The design of this study, with its relation to demographic and individual diversity, could serve as a model for studies of populations' exposure to other consumer products.

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