My father was a pathologist at the National Institutes of Health who did some of the original work on lung cancer and particle size. He found that it was the size and shape of asbestos particles that made them particularly dangerous as cancer causing agents. What Scott Ray says is true. Amprphous silica is different than crystalline silica in structure so therefore is not such a problem and silica is not as bad as asbestos. If anyone is interested, you can look up research by Mearl F. Stanton, in the 1960-1980.

Hope Stanton
Nehalem, OR

S c o t t R <mryakima at nwinfo.net> wrote:
While there may or may not exist veridical health problems associated with
DE inhalation, during the short 1.5 year average life span of most
passerines, including swallows, the development of lung cancer seems
questionable.

Many people mistakenly believe that because DE is a silica meterial, that
it can cause silicosis. It cannot. DE is amorphous silica which, unlike
crystaline silica, does not cause silicoses. DE has been and continues to
be deemed a safe insecticide for use in human dwellings.

Any finely divided material can pose a hazard to the lungs. I read
somewhere that road dust (which has a high crystalline silica component)
is more hazardous to human lungs than DE. Like all cavity nesting birds,
cavity nesting swallows are certainly exposed to a huge amount of airborne
dust particles of another form, shed feather sheathes.

Scott R a y
Yakima, WA

> As far as I know DE is NOT non-toxic. While it may
> not contain chemically toxic compounds, it is very
> harmful to the lungs. Warnings on the label advise
> not to breath it. I have worked around this substance
> quite a bit, in gardens, and at wineries for use in
> filtration. Small particulates are very harmful to
> the lungs, and are one of the main causes for lung
> cancers. I see that the abstract does not mention
> anything about mortality rates of the Tree Swallows,
> as a two year study would have difficulty looking at
> that.
> I know how sensitinve my lungs are, and can only
> imagine the possible sensitivity a 15- 20 gram bird
> might have to a substance such as this, in its packed
> and tight living quarters, with young birds moving
> around, ruffling their feathers, wrestling for the
> next delivery of food, etc...
> Not poo-poooing the idea, nor the study, but as we
> endeavor to "manage" our wild, native birds we must
> think about every possible facet, and it seems in this
> case one was overlooked.
> Drew Wheelan
> Maple Falls, WA
> awheelan at hermaninstitute.org
>
>
>
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