Granular biodurable nanomaterials: No convincing evidence for systemic toxicity

Abstract

Nanomaterials are usually defined by primary particle diameters ranging from 1 to 100 nm. The scope of this review is an evaluation of experimental animal studies dealing with the systemic levels and putative systemic effects induced by nanoparticles which can be characterized as being granular biodurable particles without known specific toxicity (GBP). Relevant examples of such materials comprise nanosized titanium dioxide (TiO₂) and carbon black. The question was raised whether GBP nanomaterials systemically accumulate and may possess a relevant systemic toxicity. With few exceptions, the 56 publications reviewed were not performed using established standard protocols, for example, OECD guidelines but used non-standard study designs. The studies including kinetic investigations indicated that GBP nanomaterials were absorbed and systemically distributed to rather low portions only. There was no valid indication that GPB nanomaterials possess novel toxicological hazard properties. In addition, no convincing evidence for a relevant specific systemic toxicity of GBP nanomaterials could be identified. The minority of the papers reviewed (15/56) investigated both nanosized and microsized GBP materials in parallel. A relevant different translocation of GBP nanomaterials in contrast to GBP micromaterials was not observed in these studies. There was no evidence that GPB nanomaterials possess toxicological properties other than their micromaterial counterparts.

Keywords:

• carbon black
• low-toxicity dusts
• nanotoxicology
• nuisance dust
• poorly soluble low toxicity particles
• systemic toxicity
• titanium dioxide

Acknowledgements

We thank Ivan Dobrev and Bruno Orthen for critically reading and help improving the manuscript and Sven H. Smilgeit for technical support.

Declaration of interest

MMH is employed by the Berlin Office for Occupational Safety, Protection of Health and Technical Safety (LAGetSi). His duties are in the field of occupational inspection and legal enforcement. MMH does not have any specific professional responsibilities related to nanomaterials. His involvement in the present work is due to a thesis in postgraduate education in toxicology. TG is working at the German Federal Institute for Occupational Safety and Health (BAuA) which conducts research and development in the field of safety and health at work. BAuA is a governmental research institution within the purview of the Federal Ministry of Labour and Social Affairs. TG is involved in the toxicological evaluation of workplace chemicals both with respect to hazard classification and occupational exposure limit setting in Germany. This includes nanomaterials. TG is further involved in funding extramural research on nanomaterials by BAuA. The review, synthesis and conclusions reported in this paper are the exclusive professional work product of the authors and may not necessarily represent the views of their employers.