For context, quoting from Wikipedia:
"The acute toxicity of the compound was demonstrated by the death of heavy metal chemist Karen Wetterhahn, who died 10 months after a single exposure of only a few drops permeated through her disposable latex gloves."
Which reminds me of another, bit more common, chemical: hydrofluoric acid. It's a nasty substance that - in low enough concentration - can penetrate your skin, killing cells on its way to the bones, and disrupt the work of internal organs, with symptoms only visible after hours have passed.
https://en.wikipedia.org/wiki/Hydrofluoric_acid_burn
Not to scare people too much, but the last 100 years have given us a tremendous amount of tools to do harm, a lot of which are available to smart and determined enough individuals. At this point it's evident that the reason humanity hasn't already self-destructed is that most people aren't crazy maniacs and don't want to kill (at least not at random). Bioweapons are particularly nasty here because they self-replicate. It's not like with nuclear weapons, where the limiting factor is that the infrastructure necessary to weaponize fission material is affordable only for state-level actors. For bioweapons, all you need is base pathogen, some (arguably expensive) lab equipment, and a smart enough crazy.
Honestly, it's not alarmist at this point and it's not just limited to bioweapons. A whole host of chemicals such as dimethylmercury exist and could potentially be weaponized.
Science and technology advance relentlessly; at some point we will have to figure out how to apply our new capabilities to achieve surveillance without the dystopian part. Unfortunately, current political processes don't lend themselves to this.