Evaluating the sensitization potential of surfactants: Integrating data from the local lymph node assay, guinea pig maximization test, and in vitro methods in a weight-of-evidence approach Nicholas Ball a , Stuart Cagen b , Juan-Carlos Carrillo c , Hans Certa d , Dorothea Eigler e , Roger Emter f , Frank Faulhammer g , Christine Garcia h , Cynthia Graham i , Carl Haux j , Susanne N. Kolle g , Reinhard Kreiling k , Andreas Natsch f , Annette Mehling l,⇑ a Dow Europe GmbH, Horgen, Switzerland b Shell Health, Houston, TX, USA c Shell International BV, The Hague, Netherlands d SASOL Germany GmbH, Marl, Germany e Evonik Goldschmidt GmbH, Essen, Germany f Givaudan Schweiz AG, Dübendorf, Switzerland g BASF SE, Ludwigshafen, Germany h SEPPIC, Paris, France i Huntsman Corporation, The Woodlands, TX, USA j Akzo Nobel Surface Chemistry AB, Stenungsund, Sweden k Clariant Produkte (Deutschland) GmbH, Sulzbach, Germany l Cognis GmbH (now part of BASF), Henkelstr. 67, 40551 Düsseldorf, Germany article info Article history: Received 9 March 2011 Available online 27 May 2011 Keywords: Alternative methods Skin sensitization Guinea pig maximization test (GPMT) hCLAT Irritation KeratinoSens assay Local lymph node assay (LLNA) Peptide reactivity assay Regulatory tests Weight of evidence abstract An integral part of hazard and safety assessments is the estimation of a chemical’s potential to cause skin sensitization. Currently, only animal tests (OECD 406 and 429) are accepted in a regulatory context. Non- animal test methods are being developed and formally validated. In order to gain more insight into the responses induced by eight exemplary surfactants, a battery of in vivo and in vitro tests were conducted using the same batch of chemicals. In general, the surfactants were negative in the GPMT, KeratinoSens and hCLAT assays and none formed covalent adducts with test peptides. In contrast, all but one was posi- tive in the LLNA. Most were rated as being irritants by the EpiSkin assay with the additional endpoint, IL1- alpha. The weight of evidence based on this comprehensive testing indicates that, with one exception, they are non-sensitizing skin irritants, confirming that the LLNA tends to overestimate the sensitization potential of surfactants. As results obtained from LLNAs are considered as the gold standard for the devel- opment of new nonanimal alternative test methods, results such as these highlight the necessity to care- fully evaluate the applicability domains of test methods in order to develop reliable nonanimal alternative testing strategies for sensitization testing. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction An integral part of hazard and safety assessments for consumer and occupational health is the estimation of a chemical’s potential to cause allergic contact dermatitis. Currently animal tests are typ- ically used in a regulatory context to assess a chemical’s potential to induce skin sensitization. Both the murine local lymph node as- say (LLNA; OECD 429) and guinea pig based tests (GPTs, OECD 406; guinea pig maximization test (GPMT) or Buehler tests) are test methods accepted by the regulatory bodies to assess this endpoint. As a 3R method, the LLNA has become the preferred method for sensitization testing in the European Union (EU) and increasingly in other countries. Within the EU, the new chemicals legislation on the registration, evaluation, authorization and restriction of chemicals (REACH) requires the submission of information on hu- man health effects of chemicals. With few exceptions, all sub- stances registered in accordance with REACH will require skin sensitization data. Within the framework of REACH, the local lymph node assay (OECD, 2010) is the preferred method for gener- ating data on skin sensitizing potential. Use of other methods, including the traditionally used guinea pig tests (OECD, 1992) may only be performed under exceptional circumstances when sufficient scientific justification warrants their use. 0273-2300/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.yrtph.2011.05.007 ⇑ Corresponding author. Fax: +49 211 2006 19209. E-mail address: Annette.Mehling@Cognis.com (A. Mehling). Regulatory Toxicology and Pharmacology 60 (2011) 389–400 Contents lists available at ScienceDirect Regulatory Toxicology and Pharmacology journal homepage: www.elsevier.com/locate/yrtph