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Re: Purity Of Organic Foods
At 08:08 AM 11/25/02, you wrote:
"Some pesticides also may be present, particularly in grass clippings, but
again the levels ordinarily are expected to be too low to pose any concern.
An unconfirmed 1991 study in Illinois found low levels of 19 pesticides in
composting yard wastes. The concentrations were so low that all except one
of the 44 samples met the levels allowed in raw agricultural commodities for
the 13 detected pesticides for which such levels have been established. (No
levels are set for the other 6, which were mostly banned pesticides no
longer in use.) In samples from 6 sites in New Jersey only one pesticide,
chlordane, was detected. Since chlordane is no longer used, and since it is
not taken up by plants,
Chlordane is taken up by plants. Cucurbits draw it into their flesh and can
actually concentrate it in their seeds to a level equal to the soil
concentration. I know that this was taken from the above website but it is
certainly in contradiction to the data I have seen here in Oregon. This can
be a real problem for pumpkin seeds, pickles, etc.
it is believed that this came from the residential
soil mixed with the yard waste during raking or bagging.
Based on these considerations and findings, yard waste compost is considered
safe for residential use without specific testing. The only exception to
this would be for composts containing materials from golf courses, where
more intensive use of more toxic and persistent compounds is common. Such
materials may require testing for specific metals and pesticides before
A more careful approach is now warranted due to the clopyralid problem.
(Moment of silence while we all thank Dow Chemical.)
"Researchers F.C. Michel and C.A. Reddy at
Michigan State University studied the fate of three
commonly used lawn chemicals during composting:
diazinon, 2,4-D, and pendimethalin (Prowl). A
laboratory scale compost system was used for leaves
and grass (in a 2:1 ratio) amended with radiolabeled
pesticides at levels typical for incoming feedstocks at
a commercial compost operation. Evolution of
labeled CO2 was a primary indicator of pesticide
About 50% of the 2,4-D was mineralized to CO2,
compared to only 10-13% of the other two pesticides.
Leaching and volatile losses were low. The
researchers then searched for the fate of the
remaining carbon. Much of the labeled carbon from
all three pesticides was associated with the humic
materials or was unextractable from the final
composts. These pesticide residuals appeared
chemically quite different from the parent compounds
and less available to plants and animals. Thus, while
complete mineralization did not occur, decomposition
appeared to eliminate the pesticides as bio-active
Researchers at the University of Guelph are studying
the fate of 2,4-D, mecoprop and dicamba applied to
turf and then composted. They measured a 78-87%
loss of the herbicides over 10 weeks of composting.
But the mass of compost declined by 92%, leading to
an increase in the concentrations of the herbicides.
More recently, there have been several instances of
phytotoxicity from composts produced in Washington
State. A relatively new lawn herbicide from Dow
Chemical called 'Confront' (clopyralid) appears to be
causing herbicide damage on plants grown with the
compost from the Spokane, Wash., facility. Confront
is intended to provide residual weed control in the
soil. The product label specifically states "Do not
use compost containing grass clippings from turf
treated with Confront in the growing season of
The herbicide has a half-life of about 250 days. The
60-90 day composting process at Spokane did not
break down the material. Clopyralid was present
only in trace amounts in the compost and in the
plants. The limit of detection is 0.03 ppm, and levels
were below that. Even so, enough herbicide was
present to kill tomato plants.
Recently, a two-part literature review of the fate of
pesticides in composting was published in Compost
Science and Utilization (Buyuksonmez et al.; Fall
1999, Winter 2000). While the recent problem with
Confront was not included, the authors generally
concluded that pesticide degradation in compost is
similar to that in soil. Compost may have different
microbial communities, higher temperatures, and
more active organic matter. But those pesticides that
are persistent in soil and cause residual phytotoxicity
may exhibit the same problems in compost and
should be candidates for more careful monitoring
than pesticides that routinely degrade."
In a word, life is complicated, and a blanket assurance that pesticides are
degraded by composting is not fully adequate in the Brave New World we live
Like others on this list, I do collect substantial quantities of fall
leaves, which are the backbone of my composting and vermicomposting. I rely
on the general virtues of degradation that I know I can expect from
composting, and I tend to stay in the higher range of C:N values, which
favors the fungal growth which I understand is most likely to degrade
There may be some chlordane in my area, even though it has been banned for
more than a decade, since it was once recommended as a lawn and garden
insecticide. As far as I know, there is not any use of clopyralid in the
local lawn chemical industry.
It could be in food wastes, though. The Canadian government recently
approved clopyralid residues in food materials at levels as high as 7 ppm.
Brave New World, indeed!
----- Original Message -----
From: "Dale Wilson" <nosliwelad@YAHOO.COM>
Sent: Monday, November 25, 2002 5:56 AM
Subject: Re: [SANET-MG] Purity Of Organic Foods
> > My wife complains that when I collect the 80 or more bags of leaves
> > from my neighbors that they may have sprayed their trees or worse yet
> > leaves may have touched the spoiled grass, tainted by fertilizers.
> When I read this I thought of one of my favorite passages from the
> bible "Love covers a multitude of sins." The "deep Basidiomycetic
> penetralia of the soil" (to quote E.O. Wilson) is like love. With very
> few exceptions, everything is broken down and recycled in the pile and
> in soil, and pretty soon everything is "natural."
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