Hm, I just did a bit of research and it's a little weird the lack of concensus on the first page. Nothing about it being a carcinogen or mutagenic. I'd be more worried about infecting myself with some kind of dormant algae that produces cyanotoxins. And it appears that the damage caused by repeated inhalation of non-food grade DE is what is carcinogenic. Are you a health industry shill?