What would increase the sulfur component of onions? I think that is the problem.
Additives sprayed on possibly used to increase shelf life maybe? I used to be a trucker and hauled a load of onions out of southern Arizona to St Louis about 27 years ago. They were iced down in a refrigerated truck. Or maybe the icing down is no longer used because of cost. Ice after you cut an onion helps keep them fresh and takes some of the strongest taste out.