This is the second time in recent years (because I bought two pairs in that timespan) that my new Koss KSC 75 come with distinctly smelly rubber foam pads. It is unpleasant and rubs off on hands and other skin (although seemingly less so than last time), so I am uncomfortable with using them, since I don't know what chemicals are used there, but since it's a US brand that surely manufactures in China, I don't know whether chemical guidelines here in the EU are obeyed.
I cannot say for sure whether it is an identical smell to my last pair, but back then (three years ago) it was really strong and smelled like liquefied plastic or such, and it was difficult to get rid of the smell once it was on the skin. Last time I requested replacement pads from the retailer, it was feasible, and that's another issue I have with Koss: Their pads are a ripoff: The ones that come with the headphones are large-pore, harder type rubber foam, the type that when old and dirty tends to not just tear but also erode into fine plastic sand/dust (microplastic nightmare), but when you buy their pricey 3-pairs 'replacement' pack, those are fine, soft rubber foam, and when they get old, they only tear. That was the type I got as replacement last time. And those have zero smell!
I also remember that all the KSC 75 I got in the past, before 2020, and most if not all came with the low-quality pads, did not have a smell.
Well, it is not secret that the KSC 75 are in general a quantity-over-quality, low-durability scheme. Sadly they are still the best/only option for me, all factors considered, and I am taking measures to prolong their life. (I also sent one pair in in the past due to cable breakage, but it was a hassle, and I prefer to mod them so the cable doesn't break anymore. ... Only harden, hah.)