Judy:
I too would toss it. I get about a 1/2 a pound of pollen on my cars throughout the year and I keep the cars very clean, still I would not scrap the pollen and save it - I've never found the bees to overly want pollen they have NOT collected themselves - although others have had better success at introducing pollen.
Of course the bees DID collect the pollen you are speaking of, but there is a lot of crap at the bottom of the hive boxes and it just may be a waste of time for the young workers (who would most likely be gathering this pollen up) if placed back in the hive - they have plenty of other duties to do right up until late Fall.