A publication in Cellulose this month investigated the effects of physical and chemical characteristics on cellulose nanomaterial toxicity. The authors examined toxicity after altering several characteristics of cellulose nanomaterials including their aspect ratios, surface chemistries, and methods of manufacture using embryonic zebrafish as a model. 

 The authors conclude that both cellulose nanocrystals and cellulose nanofibrils have an overall low toxicity. Based on their results, they do not consider the high surface area of these materials as a predictor of their toxicity, and for relevant exposure concentrations, their hazard is low.

 High aspect ratio cellulose nanofibrils produced through mechanical methods were relatively more toxic than cellulose nanocrystals and nanofibers produced through chemical synthesis methods. Investigations into the effect of changing surface chemistry, resulting in positive, negative and neutral charge, had a minimal influence on the hazard of cellulose nanocrystals. Further, an uptake study of fluorescently labelled cellulose nanocrystals found that over the course of a 5 day exposure, CNC was taken up both dermally and orally, with no observed toxicity even at extremely high levels of exposure (2000 mg/L).  Together, these results add to a growing list of reports suggesting that cellulose nanomaterials have a benign nature and low hazard.