Development of a database on toxic effects of nano-objects

Nano-objects are considered to be more toxic than fine dust of the same substance. Due to the heterogeneous data (e.g. composition, shape, surface) of the objects and the many different study designs used for investigations, it is difficult to overview the publications and to draw common conclusions. Therefore, based on the RepDose database of Fraunhofer ITEM, the PaFtox database was developed which contains repeated dose toxicity studies with nano-objects applied via inhalation and instillation. Currently, the database PaFtox comprises 131 inhalation studies and instillation studies with rodents with particles of titan dioxide, carbon black, silicon dioxide, metals or metal oxide, and carbon-nanotubes (study duration > 28 days). The particle characterisation (primary and secondary) in the literature is very heterogeneous and only seldom sufficient; e.g. the specific surface is not provided for all nano-objects. Properties of particles can be categorised and these categories can be used for LOEL analyses. The analysis related to the diameter category of particles <= 56 nm and > 56 nm reveals, that the LOELs of nano-objects are by a factor of 18 (median) lower than the LOELs of larger objects. The scope of the studies strongly differs, regarding the parameter (effects) determined as well as the related time points of investigations. Therefore, analyses of effect sizes are limited to frequently measured effects like neutrophil number, total protein and LDH content in BALF, or infiltration observed in the lung. The PaFtox database offers the opportunity of a systematic and structured analysis of the available literature of particle toxicology. The ultimate goal is to use the database as a tool for identifying physicochemical properties that either are related to toxicity or to cancer.