Contribution of new technologies to characterization and prediction of adverse effects.

Identification of the potential hazards of chemicals has traditionally relied on studies in laboratory animals where changes in clinical pathology and histopathology compared to untreated controls defined an adverse effect. In the past decades, increased consistency in the definition of adversity with chemically-induced effects in laboratory animals, as well as in the assessment of human relevance has been reached. More recently, a paradigm shift in toxicity testing has been proposed, mainly driven by concerns over animal welfare but also thanks to the development of new methods. Currently, in vitro approaches, toxicogenomic technologies and computational tools, are available to provide mechanistic insight in toxicological Mode of Action (MOA) of the adverse effects observed in laboratory animals. The vision described as Tox21c (Toxicity Testing in the 21st century) aims at predicting in vivo toxicity using a bottom-up-approach, starting with understanding of MOA based on in vitro data to ultimately predict adverse effects in humans. At present, a practical application of the Tox21c vision is still far away. While moving towards toxicity prediction based on in vitro data, a stepwise reduction of in vivo testing is foreseen by combining in vitro with in vivo tests. Furthermore, newly developed methods will also be increasingly applied, in conjunction with established methods in order to gain trust in these new methods. This confidence is based on a critical scientific prerequisite: the establishment of a causal link between data obtained with new technologies and adverse effects manifested in repeated-dose in vivo toxicity studies. It is proposed to apply the principles described in the WHO/IPCS framework of MOA to obtain this link. Finally, an international database of known MOAs obtained in laboratory animals using data-rich chemicals will facilitate regulatory acceptance and could further help in the validation of the toxicity pathway and adverse outcome pathway concepts.

Guidance on classification for reproductive toxicity under the globally harmonized system of classification and labelling of chemicals (GHS).

The Globally Harmonised System of Classification (GHS) is a framework within which the intrinsic hazards of substances may be determined and communicated. It is not a legislative instrument per se, but is enacted into national legislation with the appropriate legislative instruments. GHS covers many aspects of effects upon health and the environment, including adverse effects upon sexual function and fertility or on development. Classification for these effects is based upon observations in humans or from properly designed experiments in animals, although only the latter is covered herein. The decision to classify a substance based upon experimental data, and the category of classification ascribed, is determined by the level of evidence that is available for an adverse effect on sexual function and fertility or on development that does not arise as a secondary non-specific consequence of other toxic effect. This document offers guidance on the determination of level of concern as a measure of adversity, and the level of evidence to ascribe classification based on data from tests in laboratory animals.

Use of category approaches, read-across and (Q)SAR: general considerations.

Read-across has generated much attention since it may be used as an alternative approach for addressing the information requirements under regulatory programmes, notably the EU's REACH regulation. Read-across approaches are conceptually accepted by ECHA and Member State Authorities (MS) but difficulties remain in applying them consistently in practice. Technical guidance is available and there are a plethora of models and tools that can assist in the development of categories and read-across, but guidance on how to practically apply categorisation approaches is still missing. This paper was prepared following an ECETOC (European Centre for Ecotoxicology and Toxicology) Task Force that had the objective of summarising guidance and tools available, reviewing their practical utility and considering what technical recommendations and learnings could be shared more widely to refine and inform on the current use of read-across. The full insights are recorded in ECETOC Technical Report TR No. 116. The focus of this present paper is to describe some of the technical and practical considerations when applying read-across under REACH. Since many of the deliberations helped identify the issues for discussion at a recent ECHA/Cefic LRI workshop on "read-across", summary outcomes from this workshop are captured where appropriate for completeness.

Guidance for the classification of carcinogens under the Globally Harmonised System of Classification and Labelling of Chemicals (GHS).

The United Nations Conference on Environment and Development (UNCED) has developed criteria for a globally harmonised system of classification and labelling of chemicals (GHS). With regard to carcinogenicity, GHS distinguishes between Category 1 ('known or presumed human carcinogens') and Category 2 ('suspected human carcinogens'). Category 1 carcinogens are divided into Category 1A ('known to have carcinogenic potential for humans'), based largely on human evidence, and 1B ('presumed to have carcinogenic potential for humans'), based largely on experimental animal data. Concerns have been raised that the criteria for applying these carcinogenicity classifications are not sufficiently well defined and potentially allow different conclusions to be drawn. The current document describes an attempt to reduce the potential for diverse conclusions resulting from the GHS classification system through the application of a series of questions during the evaluation of data from experiments with rodents; epidemiological data, which could lead to Category 1A, have not been considered. Answers to each question can lead either to a classification decision or to the next question, but this process should only be implemented in an environment of informed scientific opinion. The scheme is illustrated with five case studies. These questions are: (1) Has a relevant form of the substance been tested? (2) Is the study design relevant to human exposure? (3) Is there a substance-related response? (4) Is the target tissue exposure relevant to humans? (5) Can a mode of action be established? (6) Is the mode of action relevant to humans? (7) What is the potency?

Testing strategies to establish the safety of nanomaterials: conclusions of an ECETOC workshop.

The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) convened a workshop in Barcelona, Spain, in November 2005 to develop testing strategies to establish the safety of nanomaterials. It brought together about 70 scientific and clinical experts from industry, academia, government agencies, research institutes, and nongovernmental organizations. The primary questions to be addressed were the following: What can we do today, and what do we need tomorrow? The three major themes of the workshop were: (1) the need for enhanced efforts in nanomaterial characterization; (2) methodologies for assessments of airborne and internal exposures to nanomaterials; and (3) evaluation of the hazard potential--primarily focusing on pulmonary or dermal routes of exposures. Some of the summary conclusions of the workshop included the following: For the development of nanoparticle characterization, the working definition of nanoparticles was defined as < 100 nm in one dimension or < 1000 nm to include aggregates and agglomerates. Moreover, it was concluded that although many physical factors can influence toxicity, including nanoparticle composition, it is dissolution, surface area and characteristics, size, size distribution, and shape that largely determine the functional, toxicological and environmental impact of nanomaterials. In addition, most of the information on potential systemic effects has thus far been derived from combustion-generated particles. With respect to the assessment of external exposures and metrics appropriate for nanoparticles, the general view of the meeting was that currently it is not possible or desirable to select one form of dose metric (i.e., mass, surface area, or particle number) as the most appropriate measure source. However, it was clear that the surface area metric was likely to be of interest and requires further development. In addition, there is a clear and immediate need to develop instruments which are smaller, more portable, and less expensive than the currently available state of the art instrumentation. With regard to a general testing approach for human health hazard evaluation of nanoparticles, a first step to determine potency may include a prioritization-related in vitro screening strategy to assess the possible reactivity, biomarkers of inflammation and cellular uptake of nanoparticles; however this process should be validated using in vivo techniques. A Tier 1 in vivo testing strategy could include a short-term inhalation or intratracheal instillation of nanoparticles as the route of exposure in the lungs of rats or mice. The endpoints that should be assessed include indices of lung inflammation, cytotoxicity, and cell proliferation, as well as histopathology of the respiratory tract and the major extrapulmonary organs. For Tier 2 in vivo testing for hazard identification, a longer term inhalation study is recommended, and this would include more substantive mechanistic endpoints such as determination of particle deposition, translocation, and disposition within the body. Additional studies could be designed with specific animal models to mimic sensitive populations. With regard to dermal exposures, currently there is little evidence that nanoparticles at a size exceeding 100 nm penetrate through the skin barrier into the living tissue (i.e., dermal compartment). The penetration of nanoparticles at a size less than 100 nm should be a topic of further investigation. Moreover, considering the impacts of dermal exposures and corresponding hazard potential of nanoparticles, it must be taken into consideration that the dermal uptake of nanoparticles will be an order of magnitude smaller than the uptake via the inhalation or oral routes of exposure. For the evaluation of the health risk of nanoparticles, it has to be determined whether they are harmful to living cells and whether, under real conditions, they penetrate through the skin barrier into the living tissue. For the evaluation of the penetration processes, in principle, three methods are available. Using the method of differential stripping, the penetration kinetics of nanoparticles in the stratum corneum and the hair follicles can be evaluated. This analysis can be carried out in vivo. Diffusion cell experiments are an efficient method for in vitro penetration studies. Also, laser scanning microscopy is well suited to test penetration kinetics, although requiring fluorescent-labeled nanoparticles. Emerging topics such as (1) environmental safety testing, (2) applications of nanoparticles for medical purposes, and (3) pathways of inhaled nanoparticles to the central nervous system were also briefly addressed during this workshop. However, it has become clear that these topics should be the subjects of separate workshops and they are not further addressed in this report.

Chemical pollution, respiratory allergy and asthma: a perspective.

The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) convened a workshop in June 2005 to address the speculation that exposure to specific chemicals, and/or chemical pollutants in general, may play an important role in the increased prevalence of allergy and asthma in 'westernized' societies. This paper summarises one perspective arrived at during this workshop. It was acknowledged that certain chemicals and certain types of pollution might trigger or exacerbate asthmatic reactions in sensitised subjects. However, overall levels of pollution appear not to have had a major impact upon the prevalence of atopic allergy. Epidemiological studies suggest that pollution may in some circumstances protect from acquisition of sensitisation. Increasing exposure to household chemicals may enhance pre-existing allergies, but evidence for their causation of allergy is lacking. Other risk factors considered included societal dietary changes and exposure to endotoxins. Future research needs were identified which included epidemiological studies employing exposure and biomonitoring data, studies on domestic exposure to chemicals and their association with the incidence of allergy and asthma, and prospective birth cohort studies employing well-defined aspects of lifestyle, diet, chemical and endotoxin exposure as factors that may drive susceptibility to allergy and asthma.