Aligning nanotoxicology with the 3Rs: What is needed to realise the short, medium and long-term opportunities?

Nanomaterials convey numerous advantages, and the past decade has seen a considerable rise in their development and production for an expanse of applications. While the potential advantages of nanomaterials are clear, concerns over the impact of human and environmental exposure exist. Concerted, science-led efforts are required to understand the effects of nanomaterial exposure and ensure that protection goals are met. There is much on-going discussion regarding how best to assess nanomaterial risk, particularly considering the large number of tests that may be required. A plethora of forms may need to be tested for each nanomaterial, and risk assessed throughout the life cycle, meaning numerous acute and chronic toxicity studies could be required, which is neither practical nor utilises the current evidence-base. Hence, there are scientific, business, ethical and legislative drivers to re-consider the use of animal toxicity tests. An expert Working Group of regulators, academics and industry scientists were gathered by the UK's NC3Rs to discuss: i) opportunities being offered in the short, medium and long-terms to advance nanosafety, ii) how to align these advances with the application of the 3Rs in nanomaterial safety testing, and iii) shifting the focus of risk assessment from current hazard-based approaches towards exposure-driven approaches.

Guiding principles for the implementation of non-animal safety assessment approaches for cosmetics: skin sensitisation.

Characterisation of skin sensitisation potential is a key endpoint for the safety assessment of cosmetic ingredients especially when significant dermal exposure to an ingredient is expected. At present the mouse local lymph node assay (LLNA) remains the 'gold standard' test method for this purpose however non-animal test methods are under development that aim to replace the need for new animal test data. COLIPA (the European Cosmetics Association) funds an extensive programme of skin sensitisation research, method development and method evaluation and helped coordinate the early evaluation of the three test methods currently undergoing pre-validation. In May 2010, a COLIPA scientific meeting was held to analyse to what extent skin sensitisation safety assessments for cosmetic ingredients can be made in the absence of animal data. In order to propose guiding principles for the application and further development of non-animal safety assessment strategies it was evaluated how and when non-animal test methods, predictions based on physico-chemical properties (including in silico tools), threshold concepts and weight-of-evidence based hazard characterisation could be used to enable safety decisions. Generation and assessment of potency information from alternative tools which at present is predominantly derived from the LLNA is considered the future key research area.

Benefits of a silica-based fluoride toothpaste containing o-cymen-5-ol, zinc chloride and sodium fluoride.

Fluoride toothpastes in conjunction with tooth brushing are used to clean teeth, control plaque build-up and for anti-caries benefits. Toothpastes are designed with attractive flavours and appearances to encourage regular prolonged use to maximise these benefits. The incorporation of additional ingredients into toothpaste is a convenient way to provide supplementary protection that fits into people's everyday oral care routine. Such ingredients should not compromise the primary health benefits of toothpaste nor discourage its use. o-Cymen-5-ol and zinc chloride have been incorporated into a sodium fluoride (NaF)/silica toothpaste at 0.1%w/w and 0.6%w/w respectively to provide additional benefits. These include improved gingival health maintenance, in terms of the reduction of plaque, gingival index and bleeding, and an immediate and long lasting reduction in volatile sulfur compounds (VSCs) measured on breath. These benefits can be attributed to the antimicrobial and neutralisation actions of the toothpaste. The use of established fluoride models demonstrated no compromise in NaF bioavailability. The toothpaste was formulated without compromising product aesthetics. The combination of o-cymen-5-ol and zinc chloride in toothpaste gave superior maintenance of gingival health and reduction in malodour related VSCs without compromising the primary health benefits of the toothpaste or diminishing attributes preferred for the product's use.

A tiered approach to the use of alternatives to animal testing for the safety assessment of cosmetics: genotoxicity. A COLIPA analysis.

For the assessment of genotoxic effects of cosmetic ingredients, a number of well-established and regulatory accepted in vitro assays are in place. A caveat to the use of these assays is their relatively low specificity and high rate of false or misleading positive results. Due to the 7th amendment to the EU Cosmetics Directive ban on in vivo genotoxicity testing for cosmetics that was enacted March 2009, it is no longer possible to conduct follow-up in vivo genotoxicity tests for cosmetic ingredients positive in in vitro genotoxicity tests to further assess the relevance of the in vitro findings. COLIPA, the European Cosmetics Association, has initiated a research programme to improve existing and develop new in vitro methods. A COLIPA workshop was held in Brussels in April 2008 to analyse the best possible use of available methods and approaches to enable a sound assessment of the genotoxic hazard of cosmetic ingredients. Common approaches of cosmetic companies are described, with recommendations for evaluating in vitro genotoxins using non-animal approaches. A weight of evidence approach was employed to set up a decision-tree for the integration of alternative methods into tiered testing strategies.

A tiered approach to the use of alternatives to animal testing for the safety assessment of cosmetics: skin irritation.

Evaluation of the skin irritancy and corrosivity potential of an ingredient is a necessity in the safety assessment of cosmetic ingredients. To date, there are two formally validated alternatives to the rabbit Draize test for skin corrosivity in place, namely the rat skin transcutaneous electrical resistance (TER) assay and the Human Skin Model Test using EpiSkin, EpiDerm and SkinEthic reconstructed human epidermal equivalents. For skin irritation, EpiSkin, EpiDerm and SkinEthic are validated as stand-alone test replacements for the rabbit Draize test. Data from these tests are rarely considered in isolation and are evaluated in combination with other factors to establish the overall irritating or corrosive potential of an ingredient. In light of the deadlines established in the Cosmetics Directive for cessation of animal testing for cosmetic ingredients, a COLIPA scientific meeting was held in Brussels on 30th January, 2008 to review the use of alternative approaches and to set up a decision tree approach for their integration into tiered testing strategies for hazard and safety assessment of cosmetic ingredients and their use in products. In conclusion, the safety assessments for skin irritation/corrosion of new chemicals for use in cosmetics can be confidently accomplished using exclusively alternative methods.

A tiered approach to the use of alternatives to animal testing for the safety assessment of cosmetics: eye irritation.

The need for alternative approaches to replace the in vivo rabbit Draize eye test for evaluation of eye irritation of cosmetic ingredients has been recognised by the cosmetics industry for many years. Extensive research has lead to the development of several assays, some of which have undergone formal validation. Even though, to date, no single in vitro assay has been validated as a full replacement for the rabbit Draize eye test, organotypic assays are accepted for specific and limited regulatory purposes. Although not formally validated, several other in vitro models have been used for over a decade by the cosmetics industry as valuable tools in a weight of evidence approach for the safety assessment of ingredients and finished products. In light of the deadlines established in the EU Cosmetics Directive for cessation of animal testing for cosmetic ingredients, a COLIPA scientific meeting was held in Brussels on 30th January, 2008 to review the use of alternative approaches and to set up a decision-tree approach for their integration into tiered testing strategies for hazard and safety assessment of cosmetic ingredients and their use in products. Furthermore, recommendations are given on how remaining data gaps and research needs can be addressed.