Recent developments in nanoparticle (NP) technology and their commercial production have raised concern regarding NP risk to health and the environment. The toxicological characteristics of NP may not be similar to that observed in pre-NP materials because of the enormous differences in size and surface area. Thus, careful risk evaluation studies are required. Since some NP have already been produced and introduced into the market, before a suitable framework enabling risk management has been firmly established, toxicological studies based on the specificity of NP which are not subordinate to their commercial production are indispensable. The summary of nanotoxicology studies shown below clearly indicates that compared with the UK, EU, USA, and other countries, Japanese studies regarding metals and SWCNT are far from sufficient to evaluate risk.
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