Nanoparticles aren't inherently bad; after all a portion of the particle size distribution of clay sits down in the low nano range. Due to its inertness, I sus

Nanoparticles aren't inherently bad; after all a portion of the particle size distribution of clay sits down in the low nano range. Due to its inertness, I suspect gold is on the relatively safe end of the spectrum. However, whatever it's funcionalized with could certainly be an issue, and if the nanoparticles don't breakdown in the environment, multiple applications on the same field would lead to accumulation over time. There are plenty of nanoparticles that do degrade fairly rapidly, so might well be a safer alternative.