Comment by observationist

Some amount of graphene gets produced naturally. Graphite mining, processing, dyes, things that use carbon black, soot, etc - monolayer carbon structures are a byproduct of all sorts of things that humans have been exposed to throughout history. Graphene can be decomposed and metabolized; asbestos cannot, it's very stable in all sorts of places where the body cannot process it.

It doesn't mean it's good - it can do damage in the time it's present in various systems in the body, but it's not going to present a chronic, persistent threat like asbestos.

Graphene oxidizes relatively easily, and is vulnerable to all sorts of chemical processes that can attack the edges, and there are all sorts of metabolic pathways that can handle degrading and eliminating carbon. Natural decomposition from graphene in degrading concrete, asphalt, building materials, etc should handle it without any significant health risks, as well.

Some amount of graphene is present in carbon black and ground charcoal that's been used for tattoos for at least 8,000 years (Ötzi had some pretty cool tats) and hasn't presented any significant health threats.

Don't go around inhaling graphene flakes, wear sensible PPE when handling it. Acute exposure is already known to be unhealthy. That said, carbon is processed pretty well by a multitude of organisms and natural chemical processes, making the risk of chronic graphene contamination fairly low. It's a different order of hazard than asbestos entirely, and by all the evidence available so far, carbon fibers are going to be the more dangerous material.