hexane solvent extraction for oils

According to the textbook Food Science, fifth edition by Norman Potter and
Joseph Hotchkiss, hexane is a "nontoxic fat solvent" used to remove the
oil and then distilled from the oil for reuse.

It also is used as a solvent for spice oleoresins like paprika or
turmeric which are used for natural food colorings. 

I don't have the FDA toxicity data handy but I do have the following...

According to the NIOSH pocket guide to chemical hazards, 1994, hexane has
a Time waited average (TWA) of 50ppm (NIOSH ) or 500ppm (OSHA)

Time weighted average exposures should not exceed these levels averaged
over a maximum ten hour day and 40 hour work week.

Ingestion of hexane can result in nausea, headaches, peripheral
neuropathy, and numbness.

This sounds toxic . . . so

what is the actual residual hexane levels that is left in the oil after
solvent extraction and distillation to remove the hexane from the oil? 
(hexane B.P. 156 degrees F)

and what is the levels left in the oilseed meal after solvent extraction?
(which might be fed to cattle or pigs??)

Teige Davidson
Tufts University