Based on the current weight of evidence of all available data, the risk for humans from the use of nano-structured titanium dioxide (TiO(2)) or zinc oxide (ZnO) currently used in cosmetic preparations or sunscreens is considered negligible. There is a large body of information that when viewed in its entirety is considered as sufficient to demonstrate that these nano-structured ultraviolet (UV) filters, irrespective of various treatments (coatings) or crystalline structure, can be regarded as safe for use at concentrations up to 25% in cosmetic products to protect the skin from harmful effects of solar UV radiation. "Nano" TiO(2) and ZnO formulated in topically applied sunscreen products exist as aggregates of primary particles ranging from 30-150 nm in size. These aggregates are bonded such that the force of sunscreen product application onto the skin would have no impact on their structure or result in the release of primary particles. Multiple studies have shown that under exaggerated test conditions neither nano-structured TiO(2) nor ZnO penetrates beyond the stratum corneum of skin. Further, the distribution and persistence of these nano-structured metal oxides is the same compared to larger pigment-grade (i.e., >100 nm) particles, demonstrating equivalence in the recognition and elimination of such material from the body. Finally, the in vitro genotoxic and photogenotoxic profiles of these nano-structured metal oxides are of no consequence to human health. Whereas the most logical, straightforward conclusion based on data from internationally-recognized guideline studies and current 20+ year history of human use is that nano-structured TiO(2) and ZnO are safe, there will continue to be questions as "nano" conjures images of technology gone awry. Despite this rather sober view, the public health benefits of sunscreens containing nano TiO(2) and/or ZnO outweigh human safety concerns for these UV filters.

Toxicology and safety assessment are changing and require new strategies for evaluating risk that are less depending on apical toxicity endpoints in animal models and relying more on knowledge of the mechanism of toxicity. This manuscript describes a number of developments that could contribute to this change and implement this in a stepwise roadmap that can be applied for the evaluation of food and food ingredients. The roadmap was evaluated in four case studies by using literature and existing data. This preliminary evaluation was shown to be useful. However, this experience should be extended by including examples where experimental work needs to be included. To further implement these new insights in toxicology and safety assessment for the area of food and food ingredients, the recommendation is that stakeholders take action in addressing gaps in our knowledge, e.g. with regard to the applicability of the roadmap for mixtures and food matrices. Further development of the threshold of toxicological concern is needed, as well as cooperation with other sectors where similar schemes are under development. Moreover, a more comprehensive evaluation of the roadmap, also including the identification of the need for in vitro experimental work is recommended.

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