Anytime you’re burning something, you’re going to have some particles in the nanoscale due to the heat.

References

The so called ‘benefits’, watch out for the clues as to what activated charcoal really is:

1. Benefits
2. Clues that it’s nano
3. Desorption and mode of action

Carbon Black Toxicity

Smoke and soot contains nano carbons

CNT toxicity as an example

Carbon Nanomaterial Toxicity

Carbon Black ~ surface area related toxicity

Toxicity of carbon black simply from inhalation