Smaller sized nanomaterials inflict a bigger bite.
Carlson, C, SM Hussain, AM Schrand, LK Bradydich-Stolle, KL Hess, RL Jones and JJ Schlager. 2008. Unique cellular interaction of silver nanoparticles: size-dependent generation of reactive oxygen species. Journal of Physical Chemistry B doi:10.1021/jp712087m.
In this series of experiments, the particles caused damage by altering the balance of different types of oxygen within the cell, known as oxidative stress. The cells used in the experiment were a specific type of lung cell called alveolar macrophages. When exposed to the nanoparticles, they underwent oxidative stress and also changed in size. In general, particles 55 nanometer in diameter, were less toxic than the smaller, 15nm particles. But the direction of change in size of the cells depended upon the size of the nanoparticle. When exposed to particles 15 nanometers in diameter (at doses of 25 and 75 micrograms per milliliter), they shrank. But they grew larger when exposed to particles 30 nanmoeters in diameter (at the same doses).
Despite the dearth of information about nanoparticle toxicity, 235 consumer products already contain silver nanoparticles, according to a search of the Consumer Products Inventory of The Project on Emerging Nanotechnologies. These products include bandages for wound dressing, air sanitizers that aerosolize the nanomaterials into breathable particulates and personal care products intended for direct human contact. In this study, silver nanoparticles were toxic to cells by altering the oxidative balance of cells.
As nanotechnology is projected to grow to a trillion dollar industry within a decade, the likelihood of environmental and human exposures can only increase.