Sorry, but it's none of you folks which determines the acceptable levels of any of these things. In this day and age, it's regulatory agencies. And those often look at the cumulative big picture. It depends on what their radar picks up, and whether they consider it worth their fuss or not. Sometimes there is just an outright blanket ban on something. Just in this single State of there is a patchwork of regulations which affect formaldehyde per se. Move the largest local film processing lab just a few blocks north of where it presently is, and you end up with an almost draconian jurisdiction when it comes to any kind of formaldehyde usage unless a special permit is obtained - something a giant biotech corp might be able to navigate, but certainly not a photo lab.
What's off topic about it, for heavens sake? Look at the demise of a particular Fuji E-6 emulsion recently due one tiny manufacturing ingredient. Analogously, someone picks up the term "formaldehyde" on an ingredient list in a developer, and suddenly that Euro product is going to be outright banned from distribution here, and in turn, perhaps banned there too. That's just how it works. And that fact alone would tell me to rely on an alternative brand not subject to that kind of potential disruption.
That fact is, not only are most of the still extant large processing labs in the US in highly regulated municipalities, but also the distribution houses we rely on for supplies. That means high hazmat shipping charges for certain things, as well as why, right around here, the few remaining labs have had to bounce from one city or county to another as local regulations tightened. Since these same areas saw extreme pollution from chemical plants and the military in former decades, they now tend to be outright draconian; and that's what I mean by "blanket" bans on certain things. They don't want to be bothered monitoring tiny amounts, so "zero" applies to everyone.
