what is a loose spice?
I take the term "loose" to mean spices sold from large containers, scooped into a bag, rather than a sealed and packaged off-the-shelf product.



A sealed container, produced commercially, is (presumably) inspected and regulated to avoid adulteration. When you buy from an open container at a market or store, you have no way to know if it was mixed with something. 

And still, I prefer to buy fresh loose spices, from vendors I trust.