Keep the lid on the jar to keep contaminants out.
bioavailability of the contaminant.
Beware of bargains, as cutting corners to keep costs low may mean the introduction of some nasty contaminant you definitely don't want.
Some scientists suspect that a certain contaminant may be linked to the pet food supplier.
corn chamomile seed has been a contaminant in clover and grass seed.
charlock seed was a frequent contaminant of cereal seed.