The ECVAM International Validation Study on In Vitro Tests for Acute Skin Irritation: Selection of Test Chemicals

Chantra Eskes, Thomas Cole, Sebastian Hoffmann, Andrew Worth, Amanda Cockshott, Ingrid Gerner and Valérie Zuang

The ECVAM-funded skin irritation validation study (SIVS) was initiated in 2003, with the aim to evaluate whether the EpiDerm™, EPISKIN™ and the SIFT alternative methods were able to reliably identify skin irritant and non-irritant chemicals, and could therefore be candidates for replacing the rabbit Draize test for skin irritation. The primary goal of the study was to evaluate the predictive capacity of the assays with regard to the EU classification system, which employs the risk phrases, “R38”, for skin irritants, and “no label” for non-irritants. A secondary objective was the retrospective analysis of the data, to assess whether the in vitrotests would be able to discriminate between strong irritants (category 2), mild irritants (category 3) and nonirritants (no category), as defined by the OECD and United Nations proposal for a Globally Harmonised System (GHS) for the classification and labelling of dermal irritancy. A Chemicals Selection Sub-Committee (CSSC) was appointed to identify test chemicals to be used in the SIVS, for which existing, high quality in vivo data were available, with which to correlate the in vitro measurements. Since chemicals from the European Centre for the Ecotoxicology and Toxicology of Chemicals (ECETOC) database of reference chemicals for skin irritation/skin corrosion had been extensively used in preceding studies, the CSSC made use of novel sources for potential test chemicals. The first source of chemicals screened was the New Chemicals Database (NCD), which is the central archive within the EU notification scheme for ‘new’ commercial chemicals. Data registered in the NCD originate from standard assays, submitted in compliance with the legislation which regulates the marketing of industrial chemicals, and are subject to quality assurance by the competent authorities of the EU Member States. In addition, to obtain ‘existing’ chemicals which were readily available from major manufacturing and/or distribution sources, additional databases were surveyed, such as the Toxic Substance Control Act (TSCA) database maintained by the US Environmental Protection Agency (EPA), and the ECETOC database, with the exclusion of the chemicals used in the previous optimisation and prevalidation phases. A total of approximately 3500 chemicals from the NCD and 1600 from the additional databases were screened. Pre-determined selection criteria were applied, primarily to ensure the quality of the in vivo data and the practicability of their use in testing. Overall, the number of chemicals fulfilling the CSSC selection criteria was found to be limited, particularly in the case of GHS category 2 chemicals. However, a total set of 60 chemicals were selected and proposed to the Management Team of the SIVS for independent coding and supply to the participating laboratories. The selected chemicals: i) represented statistically justified sample sizes for distinguishing R38 from no-label chemicals; ii) provided a balanced representation of the three GHS categories, to allow for the post hoc evaluation of the performance of the assays for that classification system; and iii) acknowledged, to a certain degree, the large prevalence known to exist for chemicals which have oedema and erythema scores of 0. The selected chemicals represented a variety of molecular structures, functional chemical groups, and effect and use categories, as well as a wide range of physico–chemical properties. They represented a challenging set of chemicals, relevant to current industrial commerce, with which to
validate the alternative methods.
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Estimation of the Acute Inhalation Hazards of Chemicals Based on Route-to-route and Local Endpoint Extrapolation: Experience from Bulk Maritime Transport

Thomas Höfer, Derek James, Tore Syversen and Tim Bowmer

Data on acute lethal inhalation toxicity from animal studies are commonly required for assessing the hazards to human health of volatile, gaseous and dusty chemicals or their mixtures. The International Maritime Organisation (IMO) made the provision of acute inhalation toxicity data a mandatory requirement for the carriage of bulk liquid chemicals transported by sea in tank ships, thereby creating the need for inhalation data on many hundreds of chemicals in bulk maritime transport. Taking note of previously published proposals for estimating acute inhalation toxicity hazards for chemicals, and the paucity of measured experimental data, an extrapolation method has been developed by the Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) to partly fulfil this need. This method should be seen as a pragmatic approach to the challenge of missing measured experimental test data, with the added benefit of reducing tests in experimental animals. The method is based on a route-to-route (i.e. between-route) extrapolation of information on acute oral and/or dermal toxicity, in combination with data on the potential for irritation and/or corrosion to skin and eyes. The validation of this method was based on the individual evaluation of inhalation toxicity studies for 330 chemicals, including mixtures and many important chemical groups, for which the IMO holds public and industryconfidential data. The authors contend that this extrapolation method offers a reliable basis for hazard evaluation in the context of bulk maritime transport, and the ‘GESAMP inhalation toxicity extrapolation method’ has become part of the IMO regulatory system for the carriage of bulk liquids (i.e. noxious liquid substances) on board tank ships.
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Definition of the Applicability Domain of the Short Time Exposure (STE) Test for Predicting the Eye Irritation of Chemicals

Kazuhiko Hayashi, Takayuki Abo, Yuko Nukada and Hitoshi Sakaguchi

The Short Time Exposure (STE) test is a simple and easy-to-perform in vitro eye irritation test, that uses the viability of SIRC cells (a rabbit corneal cell line) treated for five minutes as the endpoint. In this study, our goal was to define the applicability domain of the STE test, based on the results obtained with a set of 113 substances. To achieve this goal, chemicals were selected to represent both different chemical classes and different chemical properties, as well as to cover, in a balanced manner, the categories of eye irritation potential according to the Globally Harmonised System (GHS). Accuracy analysis indicated that the rates of false negatives for organic/inorganic salts (75.0%), hydrocarbons (33.3%) and alcohols (23.5%) were high. Many of the false negative results were for solid substances. It is noteworthy that no surfactant resulted in a false negative result in the STE test. Further examination of the physical property data and performance showed a significant improvement in the predictive accuracy, when substances with vapour pressures over 6kPa were excluded from the analyses. Our results indicate that several substances i.e. certain solids such as salts, alcohols, hydrocarbons, and volatile substances with a vapour pressure over 6kPa — do not fall within the applicability domain of the STE test. Overall, we are encouraged by the performance and improved accuracy of the STE test.

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