I've lived in trailers and was sensitive to the formaldehyde. The worst was new trailers. But even in ones that were a number of years old I could still detect it. A burning sensation in my sinuses and such. It would seem to follow that an exposure at long term consistent levels would be a factor but also it makes sense that some people are more sensitive to *any* exposure. Wonder what this means for PN?

I posted just such a question to that author of that article you linked to.