C60 isn't toxic, in fact it is an anti-oxidant, a very strong one. Oxidative stress is sometimes desirable, though, for instance C60 is exceptional at neutralizing Nitric Oxide. You know what is one of NO's functions in the body? Erections.

After cessation, the anti-boner effects seem to disappear, though. Such a shame it even had that effect to begin with because it really made me feel more energetic and happier while allowing me to (consistently and basically within a day or two of starting to take it) do twice the reps during my workouts.