John Wolfram wrote:Diatomaceous earth is a natural silicon based product that is mined out of the ground and is generally made up of particles less than 3 micrometers in length...unfortunately, that description of DE also applies to asbestos. In a 1993 study increased rates of lung cancer were seen among DE mine workers who were in dusty DE mines of the 1950s. Since DE's pesticide properties are based on a mechanical action, it does not seem unreasonable to believe that, like asbestos, the carcinogenic properties of DE would also be due to a mechanical action that irritates the cells in the lungs.
One positive note about that 1993 study is that it states that once the dust level was brought down there was not a statistically significant increase in cancer among the workers.
Justin Wood wrote: Several things to note are the lack of masks worn by workers, the mix of asbestos and DE (which one worker then wipes under his nose!), and the extended time of exposure these workers were around DE dust.