Why not require that any returned material be cleaned and (if necessary) sterilized prior to being returned? Put the onus on the customer for protecting everyone in the chain!
In a past life I worked for a medical devices company and we put this policy in place after receiving a device back that scared the poop out of our Returns Coordinator. The device is designed to come in contact with blood and tissue during surgery. When we opened the box, there was our device, bloody, along used needles and a half used bottle of Heperin. Obviously it came right from the surgical suite. :mg:
After that we insisted on cleaned and sterilized product. Our Returns Coordinator also was required to get the Hepatitis vaccine.
In my present job, which is as far away as you can get from medical devices, we got some product back from a meat packing plant that had pig hair and guts attached to it. No hesitation on my part: we rejected it back to the customer and required that it be cleaned before we'd touch it. Animals can transmit disease too.
You have to protect your people and everyone in the transportation chain!