The article posted by vgvball shows that the SW (i.e. Arizona and California) are hot spots for NTM, not low spots. I developed NTM while living in the Tucson area. (I believe Terri Martin also did.) We switched between Arizona in winter and SE Michigan in summer for a few years. I now live in Michigan full time, which has much less NTM, according to the same article (although my NTM ID doctor at U of Michigan said he sees lots of people with NTM). I also lived around Denver for many years before that. We left for Arizona because the air pollution in the Dever area was giving me lots of trouble. (Maybe I first got NTM there??) https://pubmed.ncbi.nlm.nih.gov/22312016/#&gid=article-figures&pid=figure-1-uid-0.