Adjuvants, even aluminum based adjuvants can be safe from a toxic perspective. The mercury based preservatives like Thimerosol are claimed to be safe. I had a mercury based contrast injected into my veins for a brain scan in 1970.

My concern is they trigger the immune system to go looking for an invader. Evidence suggests that in some cases of adjuvant based dead cell vaccines, when the immune system goes looking for the invader and does not find one, it gangs up on whatever looks like the dead cells. In some cases, it is believed that it attacks health cells that have a resemblance to the dead cells but the body needs to function. Many believe this is the start of some auto immune diseases.