But the activated charcoal too contains all kinds of structures, including nanotubes. It's the filter construction that prevents them to end up in water (and th

But the activated charcoal too contains all kinds of structures, including nanotubes. It's the filter construction that prevents them to end up in water (and they are much less dangerous in water than in air). If it can filter 3 times as much water before needing to be replaced, why not?