I think a fact of life is that there are MANY contaminants (especially solvents) in ALL the products we use, including some foods, vitamins for foods, etc. NO chemical process is perfect and NO purification process is perfect.

The best thing is to use solvents that are relatively safe in tiny concentrations. In that regard, about the only common solvent that has been discovered to be a risk is benzene--because a single molecule of it can intercalate into a single DNA molecule of a single cell--and perhaps cause a replication error in that cell which will give rise to a transformed cell, which can turn into a cancer.

TINY amounts--such as the occasional molecule caught in a crystal structure--of the solvents we use in extractions aren't a problem.