The threads I talked about the problem with wood is in this section, I think they were threads about dustless litters.
In case anyone wonders why I don't search and post the threads, search+my phone just doesn't work. Something about it either refuses to search altogether or it crashes my browsers.
The medical texts and studies are pdfs and copied paged from previews on Google Books. I don't book mark links to things already saved on my computer. But anyone can find a lot of great info by looking things up. The terms I used were "feline chronic progressive inflammatory bronchitis" and variations of that. "Inflammatory feline lower airway disease", etc. Mine don't have asthma, thus I don't look up asthma as a search term and can get passed laymen sites that only focus on that. (For example, has anyone just getting their info from such sites found much on emphysema and COPD?)
The fabcats site already linked to in this thread is hit and miss, my main problem with it being that in one part they acknowledge bronchitis as it's own disease, but in another claim it's asthma.
Regardless of that their list of triggers is correct and wood is on there. So are grains, as litter and food. You have but to look at all the cats allergic to grains in their food to realize it's a serious potential allergen.