ABSTRACT
Although more and more nanomaterials (NMs) continue to be produced with almost innite variations in size, shape, structure, and surface modications (Lövestam et al. 2010), a generally applicable paradigm for NM hazard identication and risk assessment is not yet available. Not only their physicochemical characteristics may have an impact on the extent and type of biological effects they induce, additionally, unlike conventional chemicals, exposure to NMs is not to a distinct type of molecule, but to a population of primary particles, aggregates, and agglomerates of various sizes and different surface coatings that may change in characteristics with time (compare Chapter 4 and Section III). These characteristics can inuence exposure and kinetic behavior, as well as the type of effect of the NM. This complicates classical risk assessment approaches and multiplies the need for efcient and effective hazard testing and exposure assessment.
