Except non is not an english word, it is a prefix of latin origin. Which is why american style manuals will always ask you to merge it with the subsequent word, without a hyphen. British rules differ, and … The bound morpheme non is the negator for life-threatening here, so 'life-threatening' is more coherent.
Understanding the Context
This does not come across with nonlife-threatening, which would seem to imply a threat to non-life. Is there any difference in usage between inconclusive and non-conclusive (nonconclusive)? Inconclusive is more popular in research compared to non-conclusive, using pubmed search, 20,872 and 260 …
