How did you get glass and plastics in the asphalt? During the milling operation dust may be generated so I would wet the asphalt before milling and spray additional water from the discharged milled material. The workers and operators would be required to wear proper respirators while operating the milling equipment and while loading their dump trucks as milling continues. When reprocessing milled asphalt, I imagine that the plastic will burn off when the milled asphalt is recycled and mixed with new asphalt in a kiln. Glass may soften but I doubt it as the kiln temperature may not be high enough. Dust and fumes may be your greatest hazards so if in doubt, contact the industrial hygienists of your commercial insurance company to perform air sampling tests on the operator(s) of the milling equipment, the driver(s) of the dump truck(s) and those on the ground helping the milling operator(s) from contacting any metal covers protruding thru or imbedded in the asphalt. The insurance industrial hygienist will be in a better position to advise you.