Here's a video I found about some research done on potassium sorbate:
The conclusion of the researchers is that Potassium Sorbate is a genotoxic and mutagenic compound.
Genotoxic: damaging to DNA: pertaining to agents known to damage DNA, thereby causing mutations, which can result in cancer.
Mutagenic: An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism
How about PS in a positive light?
"consumption of potassium sorbate is non-toxic -- even when taken in large quantities -- and breaks down in the body as water and carbon dioxide"
Either way, we're not eating it. It's synthetic.