Pool Filters

• DE is one of three types of material used for pool filters, sand and pleated synthetic filters being the other two. Pool-grade DE differs from natural DE in that it has been heat-treated, crystallizing the silica content. These crystals are a respiratory hazard to humans, so pool-grade DE can't be used as an indoor pesticide.
  
  

Effect On Insects

• Natural DE, used as an insecticide, does not kill directly, like a poison, but instead works as a desiccant, drying up bugs that scrape across its sharp edges.
  
  

Insects Affected By DE

• DE works on most insects, including bedbugs, ants, cockroaches, fleas, flies and snails. It does not work on earthworms, which can digest DE.
  
  

Bedbugs

• To use DE to combat bedbugs, put the bed legs in cups, then put DE into the cups. This barrier scrapes the wingless insect on its way to the mattress.
  
  

Health Effects On Humans

• Natural (food-grade) DE, as opposed to pool-grade DE, is safe for humans, according to Golden Harvest Organics. DE can be applied to pet and farm animal coats to kill fleas and flies; zoos even incorporate it into animal diets to kill off internal parasites.