Background: The widespread application of nanotechnology in the last decades, the increasing
likelihood of human exposure to nano-sized materials, together with the still limited knowledge
concerning their toxicological profile, require a careful risk assessment, particularly in occupational
settings. However, a specific “risk assessment paradigm” for these peculiar xenobiotics has not
yet been defined.
Objective: The aim of this review was to address those critical aspects that currently prevent the
achievement of a suitable risk evaluation in order to point out priorities of research helpful to develop
and implement an effective guidance for nano-risk assessment.
Method: Literature search concerning NM physico-chemical characterization, toxicological behavior
and exposure assessment strategies was analyzed to extrapolate opportunities, challenges and criticisms
in the application of the general chemical risk assessment steps to the nano-sized toxicological
Results: Uncertainties on the role of the physico-chemical properties in nanomaterial toxicity, the
complexity in extrapolating dose-response relationships, and practical difficulties in measuring
nanomaterial exposure emerged as challenging issues for the application of a traditional risk assessment
approach to nano-sized exposures.
Conclusion: Future investigations on these topics appear necessary to define an effective, nanofocused
risk evaluation strategy that should be dynamically improved and verified as more substantial
information become available. Such a suitable risk assessment process should provide adequate
estimates of nanomaterial risks to guide the adoption of appropriate risk communication and management
strategies for the protection and the safety of the workers.