When I was an undergraduate in the mid-seventies, glyphosate was sort of
a miracle herbicide. We were taught that it is rapidly immobilized in
the environment, and then degraded. With an LD50 of about 5g/kg it was
a lot safer than other herbicides in terms of acute toxicity. I have
used Roundup quite often, and it seems to be bound and inactivated
immediately by the soil. It sure is bad though when the spray drifts
onto corn or cucurbits! Also, some broadleaf weeds appear somewhat
resistant. Additional surfactant appears to improve it a great deal.
When the matter came up on Sanet a while back, I pulled about 100
references out of Agricola on the toxicology and persistence of
glyphosate, since I had never personally looked at the primary
literature on this subject.
Perusal of the abstracts tended to support safety. Apparently you have
to drink about 300 ml of Roundup concentrate to kill to yourself.
Glyphosate from small oral doses is about 99% eliminated via the urine
in about a week. It is not absorbed through the skin very easily. Even
applied directly to water for control of aquatic weeds, glyphosate
doesn't have much effect on aquatic animals, or submerged plants.
Surfactants can increase toxicity to aquatic animals. It is bound
rapidly by colloids in soil and water and is broken down in a few weeks
by bacteria. Frequent applications can reduce rate of earthworm growth.
If people are interested, they should read these papers, not just the
abstracts, and see how credible the work was. If anyone is interested,
I'll send them the search results.
> I have read Caroline Cox's 48 page compilation of
> references indicating problems with Roundup in
> the Journal of Pesticide Reform.
Have you got that in electronic format? I'd like to look at it.
> Is all this, to use Dr. Trotter's term, 'junk science'? And if it
> is, how do we avoid the other side of the coin, 'whore science'?
Anything that is not peer-reviewed is immediately suspect. If it is
peer-reviewed, what is the nature of the community? I tend to discount
sources that are intentionally polemic. I would take a source like "J.
Pesticide Reform" with a grain of salt, just like I would Monsanto trade
literature. Journals published by long-standing scientific societies
with a tradition of scholarship are probably reliable. Ultimately one
has to dig in the literature, read the papers, and judge for themselves.
Dale Wilson
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