Toxicity of Nanoparticles - Hype or Reality

Sunnuntai 8.4.2018 klo 12.27 - Mikko Nikinmaa

During the recent past, the toxicity of nanoparticles (i.e. particles with at least one dimension less than 100 nm) has become a very fashionable field of toxicological studies. There is now ample evidence that the particles can be toxic, if their concentration is high enough. And that is the major problem of most nanotoxicological studies: the nanoparticle levels are often thousands of times higher than what can be expected to occur in the environment. Since one has now clearly shown that nanomaterial can be toxic, it would be high time to study the possible environmental relevance of the toxicity. If there is none, then the studies showing toxicity are irrelevant. This is because one can find toxic amount of any substance. For example, one can demonstrate a lethal dose for water. As Paracelsus said already in 16th century: All substances can be poisonous, the dose makes the difference between remedy and poison.

A significant problem with nanomaterial studies is that the methodology used is suitable especially for dissolved substances in aquatic media, but is not necessarily suitable for the new material. Hitherto, methods, which would be specific and good for nanomaterial research have not been developed. A significant property of nanomaterials is their tendency to aggregate, and the influence of this on the toxic properties is poorly described - it makes definitely a big difference if aggregation occurs before the contact with organisms or only after cellular uptake. One toxic effect of nanomaterials, which is independent of their metal components, is that they cause oxidative stress (and inflammation). This property may get worse with aggregation - we do not know. As the worst possible scenery one can think that nanomaterials cause similar problems in airways as asbestos: this may be fearmongering, but until environmentally relevant nanotoxicology studies are available, the possibility cannot be discounted.