I just quickly read thru the link to the vinyl engine thread, and it seems they are talking about different things; the snip from the article re the BBC seemed to be talking about inner sleeves, but the discussion then migrates to the effect of jacket sleeves interacting with the poly inner. I assume polyethelene also uses a plasticizer for flexiblity, but would be interested in knowing if the leeching properties are the same as PVC. I could see some interaction being theoretically possible from outer bag to inner sleeve to record itself, but hmmm, maybe 4-6,000 records stored in poly outer bags with high quality inners. The other 6 or so thousand in NY I haven't gone through yet, so maybe no more outer bagging? I've had records that I bought in the 70's that are still great players, and only in later decades did I replace inner sleeves and/or add an outer bag. The only record that comes to mind with the problem described was a now out of print Cisco Aja that had a white foggy mark -a line about an inch long and a quarter inch thick, somewhat irregular, on both sides. Cleaning, including enzyme and ultrasonic, did not remove it. But, as I recall, it didn't affect the sonics. (My go to is an AB of that record anyway, but whatever).