Has a study ever been done?
 

As to the levels of "uncleanness" between "new" items in a regular store and "used" items found in secondary markets (yard/garage/estate sales and thrift/consignment shops)?

Doubtful. Interesting, though, when you consider how much the clothing and shoes are tried on, and all the other goods handled by all and sundry, Probably not a lot of difference.

I don't thing the giver thinks to disinfect items donated. That is the first thing I would do after purchase

It's been my understanding that fabric and clothing shipped from foreign countries are packed in formaldehyde to take care of any bugs that might be hitching a ride. That plus popover's.
comment re people trying on clothing that may or may not have bathed make you wonder. I did ask at several Goodwill stores in the area if they cleaned the clothing before they put it out and they said no. Can't speak to estate or consignment stores.

That's interesting - never thought about that. I am not much of a shopper, new or used items.

I think there are different kinds of contamination. There are all kinds of chemical contamination on new fabric and clothing. These are probably worse than the clothing you might buy at the second hand level. When I am lucky to pick up fabric at a yard sale or 2nd hand shop it goes right into the washer. Lots of people like to use old shirts, ties, sheets, etc. in quilts. I would always wash these before using them.

I guess I wash everything before I use it, even when I buy new clothing.

Anything I purchase gets washed before I use it, including new!!

I wash or disinfect anything I buy at a thrift store, who knows what cooties are on it.

Years ago we were helping our Son and his then wife pack and move. She had several boxes labeled "donate". I went through them and re-labeled it things for the landfill. She had stained clothes, broken toys, un-mated socks. I told her if you didn't want it, they definitely wouldn't.

I don't know much about it but the one Goodwill that my cousin used to manage, had a washer & dryer & they washed a lot of clothing items & other washable things. Also there is this second hand store at a town near by me & they also have a washer & dryer. I don't know if they wash everything or not because I have never asked them but I know they wash some things because I was in their store a few times & one of the times the washer & dryer was running. Otherwise I wouldn't even of known they had a washer & dryer. Although I never bought anything at this store I still would of washed everything at home.

I knew of a large thrift store that DID wash or dry clean ALL the clothes they sold. Ironed them too, if needed. Their prices reflected all that work and as far as I know, they NEVER put anything on sale or marked it down.