The ChemScreen project to design a pragmatic alternative approach to predict reproductive toxicity of chemicals.

There is a great need for rapid testing strategies for reproductive toxicity testing, avoiding animal use. The EU Framework program 7 project ChemScreen aimed to fill this gap in a pragmatic manner preferably using validated existing tools and place them in an innovative alternative testing strategy. In our approach we combined knowledge on critical processes affected by reproductive toxicants with knowledge on the mechanistic basis of such effects. We used in silico methods for prescreening chemicals for relevant toxic effects aiming at reduced testing needs. For those chemicals that need testing we have set up an in vitro screening panel that includes mechanistic high throughput methods and lower throughput assays that measure more integrative endpoints. In silico pharmacokinetic modules were developed for rapid exposure predictions via diverse exposure routes. These modules to match in vitro and in vivo exposure levels greatly improved predictivity of the in vitro tests. As a further step, we have generated examples how to predict reproductive toxicity of chemicals using available data. We have executed formal validations of panel constituents and also used more innovative manners to validate the test panel using mechanistic approaches. We are actively engaged in promoting regulatory acceptance of the tools developed as an essential step towards practical application, including case studies for read-across purposes. With this approach, a significant saving in animal use and associated costs seems very feasible.

Optimizing the aquatic toxicity assessment under REACH through an integrated testing strategy (ITS).

To satisfy REACH requirements a high number of data on chemical of interest should be supplied to the European Chemicals Agency. To organize the various kinds of information and help the registrants to choose the best strategy to obtain the needed information limiting at the minimum the use of animal testing, integrated testing strategies (ITSs) schemes can be used. The present work deals with regulatory data requirements for assessing the hazards of chemicals to the aquatic pelagic environment. We present an ITS scheme for organizing and using the complex existing data available for aquatic toxicity assessment. An ITS to optimize the choice of the correct prediction strategy for aquatic pelagic toxicity is described. All existing information (like physico-chemical information), and all the alternative methods (like in silico, in vitro or the acute-to-chronic ratio) are considered. Moreover the weight of evidence approach to combine the available data is included.

Integrated testing strategy (ITS) for bioaccumulation assessment under REACH.

REACH (registration, evaluation, authorisation and restriction of chemicals) regulation requires that all the chemicals produced or imported in Europe above 1 tonne/year are registered. To register a chemical, physicochemical, toxicological and ecotoxicological information needs to be reported in a dossier. REACH promotes the use of alternative methods to replace, refine and reduce the use of animal (eco)toxicity testing. Within the EU OSIRIS project, integrated testing strategies (ITSs) have been developed for the rational use of non-animal testing approaches in chemical hazard assessment. Here we present an ITS for evaluating the bioaccumulation potential of organic chemicals. The scheme includes the use of all available data (also the non-optimal ones), waiving schemes, analysis of physicochemical properties related to the end point and alternative methods (both in silico and in vitro). In vivo methods are used only as last resort. Using the ITS, in vivo testing could be waived for about 67% of the examined compounds, but bioaccumulation potential could be estimated on the basis of non-animal methods. The presented ITS is freely available through a web tool.

OSIRIS, a quest for proof of principle for integrated testing strategies of chemicals for four human health endpoints.

Chemical substances policies in Europe are aiming towards chemical safety and at the same time a reduction in animal testing. These goals are alleged to be reachable by mining as many relevant data as possible, evaluate these data with regard to validity, reliability and relevance, and use of these data in so-called Integrated Testing Strategies (ITS). This paper offers an overview of four human health endpoints that were part of the EU-funded OSIRIS project, aiming to develop ITS fit for the EU chemicals legislation REACH. The endpoints considered cover their categorical as well as continuous characteristics: skin sensitisation, repeated dose toxicity, mutagenicity and carcinogenicity. Detailed papers are published elsewhere in this volume. The stepwise ITS approach developed takes advantage of existing information, groups information about similar substances and integrates exposure considerations. The different and possibly contradictory information is weighted and the respective uncertainties taken into account in a weight of evidence (WoE) approach. In case of data gaps, the ITS proposes the most appropriate method to acquire the missing information. Each building block for the ITS, i.e. each in vivo test, in vitro test, (Q)SAR model or human evidence, is evaluated with regard to quality.

The OSIRIS Weight of Evidence approach: ITS for the endpoints repeated-dose toxicity (RepDose ITS).

In the FP6 European project OSIRIS, Integrated Testing Strategies (ITSs) for relevant toxicological endpoints were developed to avoid new animal testing and thus to reduce time and costs. The present paper describes the development of an ITS for repeated-dose toxicity called RepDose ITS which evaluates the conditions under which in vivo non-guideline studies are reliable. In a tiered approach three aspects of these "non-guideline" studies are assessed: the documentation of the study (reliability), the quality of the study design (adequacy) and the scope of examination (validity). The reliability is addressed by the method "Knock-out criteria", which consists of four essential criteria for repeated-dose toxicity studies. A second tool, termed QUANTOS (Quality Assessment of Non-guideline Toxicity Studies), evaluates and weights the adequacy of the study by using intra-criterion and inter-criteria weighting. Finally, the Coverage approach calculates a probability that the detected Lowest-Observed-Effect-Level (LOEL) is similar to the LOEL of a guideline study dependent on the examined targets and organs of the non-guideline study. If the validity and adequacy of the non-guideline study are insufficient for risk assessment, the ITS proposes to apply category approach or the Threshold of Toxicological Concern (TTC) concept, and only as a last resort new animal-testing.

The OSIRIS Weight of Evidence approach: ITS mutagenicity and ITS carcinogenicity.

Risk assessment of chemicals usually implies data evaluation of in vivo tests in rodents to conclude on their hazards. The FP7 European project OSIRIS has developed integrated testing strategies (ITS) for relevant toxicological endpoints to avoid unnecessary animal testing and thus to reduce time and costs. This paper describes the implementation of ITS mutagenicity and carcinogenicity in the public OSIRIS webtool. The data requirements of REACH formed the basis for these ITS. The main goal was to implement procedures to reach a conclusion on the adequacy and validity of available data. For the mutagenicity ITS a quantitative Weight of Evidence approach based on Bayesian statistics was developed and implemented. The approach allows an overall quality assessment of all available data for the five types of mutagenicity data requirements: in vitro bacterial mutagenicity, in vitro and in vivo chromosome aberration, in vitro and in vivo mammalian mutagenicity. For the carcinogenicity ITS a tool was developed to evaluate the quality of studies not conforming (entirely) to guidelines. In a tiered approach three quality aspects are assessed: documentation (reliability), study design (adequacy) and scope of examination (validity). The quality assessment is based on expert and data driven quantitative Weight of Evidence.

Kinetic roughening in two-phase fluid flow through a random Hele-Shaw cell.

A nonlocal interface equation is derived for two-phase fluid flow, with arbitrary wettability and viscosity contrast, c=(mu(1)-mu(2))/(mu(1)+mu(2)), in a model porous medium defined as a Hele-Shaw cell with random gap b(0)+delta b. Fluctuations of both capillary and viscous pressure are explicitly related to the microscopic quenched disorder, yielding conserved, nonconserved, and power-law correlated noise terms. Two length scales are identified that control the possible scaling regimes and which scale with capillary number Ca as l(1) approximately b(0)(cCa)(-1/2) and l(2) approximately b(0)Ca-1. Exponents for forced fluid invasion are obtained from numerical simulation and compared with recent experiments.