There are a variety of lubricants, but it is believed that the primary contributor to the problem is the organophosphate (Tricresyl phosphates - TCP / e.g. Durad 125[1]) added as an anti-wear additive.

TCP is a known neurotoxin:

"It is a toxic substance that causes neuropathy, paralysis in the hands and feet, and/or death for humans and animals alike. It can be ingested, inhaled, or even absorbed through the skin." [2]

Below is a presentation based on a PHD thesis on the subject with a lot of detail:

https://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2012...

[1] https://petrico.com/products/durad-125/

[2] https://en.wikipedia.org/wiki/Tricresyl_phosphate#Health_cal...