Parameters of nanotoxicity

Tuesday, July 18, 2006

Dr. Amanda S. Barnard from Oxford explained to Newswire that there are simply too many variables exist in our effort in predicting how nanomaterials react to organism. She gave the following examples:

1. The relationship between reactivity and size. Many materials that are inert at the macroscale can be highly reactive as nanoparticles, as for instance is the case with silver. At the nanoscale silver becomes antimicrobial, that is, it becomes bioactive. This change in reactivity cannot be predicted based on knowledge of the properties of the bulk material

2. The relationship between size and phase. Macroscopically the rutile phase of titanium dioxide is stable and the anatase phase is metastable, but when the particle size is under ~20 nm this situation is reversed. Barnard explains the intrinsic relationship between the two dependencies, size and phase: "This is of critical importance, because rutile and anatase react very differently when exposed to light. Nanoparticles of rutile are used in sunscreens, whereas nanoparticles of anatase are used in self-cleaning windows. Both technologies are currently in use around the world without discernable risk, but a phase transition in either case would do more than reduce the efficiency of these respective products, it could also be damaging to the substrate — which in the case of rutile-based sunscreen, is us. It is easy to see why there was a need for a detailed understanding of how the properties of titanium dioxide depend upon the physical structure before these products could be developed and commercialized."

Responding to the above explanations, I do think that the future regulation of nanomaterials containing products will have to embody:

1. The characterization of the products at the nanoscale level and,
2. How the materials responds to specific environment

Thus, the producer should be responsible in giving clear instruction in every operating manuals of the products. Products that are reactive in normal environment should be restricted to specific uses only. It is also important that every nano-containing products undergo a premarketing test before it is released to the market, taking the note that the said test has already comprises all "necessary" parameters. If a product contain hazard that are previously unknown, the producer should be held liable.