We’ve been told by a number of PCOs, entomologists, and DE distributors that pool grade DE is dangerous and not to use it (perhaps they also had its ineffectiveness in mind) and that we should use freshwater food grade DE.

The only dangers I was aware of from pool grade DE were respiratory, and we do remind people often that freshwater DE also should not be inhaled, and D-20 or drione (freshwater/food grade DE PLUS pyrethroids) is obviously something to be careful with. One person at least complained of an unpleasant experience with drione.

Alex, from what I understand, freshwater/food grade DE is the same stuff taken internally by people and pets. It’s in lots of foodstuffs. It may be the same as the Pharma. grade you mentioned. I appreciate all of your input, ane we are unbiased in the sense that we’ll chance our instructions and FAQs if we have good evidence pointing us towards doing so.

Cheers,
AAA

Quickly, a couple of warnings:
From a manufacturer, from a natural pesticides purveyor, and from several other websites that all seem to be reading from the same WHO document that I cannot find.

Perhaps the problem lies in the difference between freshwater and saltwater DE and the varying crystalline silica content in the different varieties available commercially.

I also remember an account somewhere by a pet owner whose cat died from the wrong kind of DE, but that can be anything and not useful as evidence.

Still, my view is that the risk of pool filter DE should not be minimized with an offhand reference to its occupational respiratory hazard! I’ll try to come up with something better tomorrow.

Regrets for not being a more spirited sparring partner.

Best.

If you understand epidemiological lingo, you might find this link useful:http://oem.bmj.com/cgi/content/abstract/58/1/38

This paper from CDC researchers published in Occupational and Environmental Medicine notes that the cummulative lifetime risk of death from lung cancer for white male diatomaceous earth miners (exposed for 45 full years of 5 day per week, 9-5 exposure to current OSHS limit of 0.05 mg of cristobalite crystalline silica per cubic meter of air) is 19 per 1000 men, with a 95% confidence interval that in reality such deaths are between 5-46 deaths per 1000 (which is pretty large spread as far as confidence intervals go).

While this is by no means insignificant and the CDC folks argue it means the current OSHA limit is too lax for DE miners, it does show that the kind of exposures you or I will see in our homes are irrelevant to our health. At no time will your house air carry anywhere REMOTELY CLOSE to 0.05mg silica/cubic meter, let alone carry such levels for any significant period of time.

Here is a link to the Material Safety Data Sheet (MSDS) for pool filter DE: http://www.inlandreno.com/pdf/m140000100.pdf

I obtained it from this link, showing it is indeed an MSDS for pool-filter DE: http://www.inlandreno.com/details.php?id=38

As you can read, pool-filter-grade DE is so NON-toxic that there is NO toxicity data given for any route of exposure. This means it is so non toxic that they couldn’t kill any test animals with it in lab experiments via feeding or other normal exposure route, let alone the death of 50% of test animals for the LD50 test listed (LD50 is shorthand for “Lethal Dose 50% of test population”).

The only toxicity they refer to is the inhalation/respiratory risk we already discussed. Crystalline silica is a lung irritant and leads to much the same cancer as does asbestos — both do this via mechanical irritation/rupture of the cells lining the lung. The constant damage and repair initiation (which requires transcribing DNA) inevitably leads to occasional translational infidelity (i.e. mutation) which can lead to cancer.

But I await your links and will defer if/when I stand corrected.

Thanks for a civil and very interesting thread, y’all.
Cheers,

As for pool-grade DE killing pets: please enlighten me/us. I’ve not found any evidence that the treatment process of DE to make it a “pool grade” filtration media makes it an ingestion toxin. What I’ve found indicates it is a respiratory hazard.

As a side note, there is also pharmaceutical-grade (or “medicine grade”) DE that is given to animals/humans to kill internal parasites. So DE by itself is pretty inert and harmless as an ingested substance.

Further, pool filter DE has no place in insect control because it doesn’t work to kill insects–the crystals are too large or something else to do with the heating process that renders it ineffective in killing insects but I’m too rushed to pin it down for you. Lou Sorkin wrote about this on the yahoo group and I’ll try to find it in a moment.

Pool filter is a definite no-no for anything but a pool. Under no circumstances. We have to stress this. Thank you!

Also, the heating and chemical treatment of DE convert some of the silica to crystalline silica, which is a respiratory hazard — though only at occupational levels (i.e. sandblasters, miners, etc.)

So natural DE is far more effective against bugs and somewhat less toxic (respiratory) than food grade — but neither is the type of hazard to get overly worried about.

This, of course, does NOT include DE which has been infused with chemical pesticides, of which there are countless formulations and varieties.

Cheers,

The pool grade is chemically treated and partially melted and consequently contains crystalline silica which can be a respiratory hazard.