[Pil-pc-oceania] Roundup toxicity & integrated weed control strategies

[Deb Guildner]

Hi All,

Full-formulation Roundup toxicity is fairly widely known, yet a surprising number of people may not realise this.  After all, Monsanto states that it is a safe herbicide, so many users may not appreciate the requirement for moon-man style safety clothing and OHS measures, especially if other people are not seen to be fussed. Many simply do not have the required patience for using alternate strategies for weed control, or do not possess sufficient ecological knowledge of a particular weedy plant to attempt an integrated approach; others are simply overwhelmed by the enormity of the task at hand, or rationalise employing a 'once-off' strategy to kick-start reafforestation etc projects.  Whatever the situation, it is always wise to adopt a less-is-better philosophy when using chemical biocides.  If the amount used is kept to an absolute minimum by employing a combination of strategies, then that is far preferable to an "it's OK to use, so why worry" approach, where the end justifies the means. Often an economic argument is put forward as a justification, where funds are extremely limited and organic (ie jute) weedmats cannot be budgeted for: a shame, as they may also save precious water, and assist young plants to grow.  Chemicals ain't OK to use, so they should only be used as a LAST RESORT, never as a first resort. 

In the case of woody weeds, eg, the plant should be cut back to as close to the base as possible, the seeds removed and prevented from growing, and only the cut stump herbicide method applied. A 1:100 concentration of glyphosate has been found to work, although sometimes a second such application is required; sometimes a maximum concentration of 10% is applied, but certainly no more. Field observers have reported that the poison can move from one such treated plant to neighbouring plants which were not treated, mysteriously killing them as well, probably via movement of the herbicide between them being facilitated by associated fungal hyphae. Death of non-target species, especially in bushland ecosystems, is a most undesirable outcome of otherwise recommended weed control.

Some years ago, when it was proven that the key surfactant in full-formulation Roundup was carcinogenic, and also fatally toxic to aquatic organisms ie frogs etc, Monsanto devised an alternate formulation, Roundup Bi-Active, specifically for use near water (replacing the offending surfactant). I would recommend that every user of glyphosate hunt down the Bi-Active formulation rather than the standard formulation: you can't be too careful.

Roundup, or glyphosate, I recall not which exactly, has also been implicated in causing non-Hodgkins lymphoma in humans. 

Many moons ago, a Brisbane-based (organic growers/) organisation published a handy little booklet titled "Pumpkins, poisons and people". It contained an article about a realtively safe herbicide, known by its trade name "Ammate" (or "Amate"), which was pricipally ammonium sulphamate, which from dimming memory was manufactured by Du Pont (alas it was discontinued....as glyphosate had been born).  Pity, because in the soil, 'Ammate' dutifully broke down into something like sulphate of ammonia. Still not brilliant, but arguably less potentially harmful than the plethora of chemical herbicides used today, including that most commonly used of all, glyphosate.

Cheers

Deb

Link to following article: http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1257636

Environ Health Perspect. 2005 June; 113(6): A403-A404. 
Copyright This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose.
Environews
Science Selections

Roundup Revelation: Weed Killer Adjuvants May Boost Toxicity (Dorothy Bonn)
Although the glyphosate-based herbicide Roundup is generally thought to be less toxic to the ecosystem than other pesticides, concerns about its effects on human reproduction persist. In a study in Ontario, Canada, exposure of male farmers to glyphosate-based herbicides was associated with an increase in miscarriage and premature birth in farm families. Seeking an explanation for these pregnancy-related problems, researchers at France's Université de Caen investigated the effects of the full Roundup formulation and glyphosate alone on cultured human placental cells [EHP 113:716-720]. The herbicide, they found, killed the cells at concentrations far below those used in agricultural practice. Surprisingly, they also found that Roundup was at least twice as toxic as glyphosate alone.

Virtually all previous testing of Roundup for long-term health damage has been done on glyphosate rather than on the full herbicide formulation, of which glyphosate makes up only around 40%. The remainder consists of inactive ingredients including adjuvants, chemicals that are added to improve the performance of the active ingredient. Roundup's main adjuvant is the surfactant polyethoxylated tallowamine, which helps glyphosate penetrate plant cells.

The Roundup concentration recommended for agricultural use is 1-2% in water. The authors incubated placental cells with various concentrations of Roundup (up to 2.0%) or equivalent concentrations of glyphosate. The viability of the cells was measured after 18, 24, and 48 hours. No one is sure how Roundup interferes with reproduction, so the team also tested whether it, like other pesticides, would disrupt the activity of aromatase (an enzyme that regulates estrogen synthesis) in placental cells. Aromatase activity was measured after 1 hour and 18 hours.

The researchers found that a 2.0% concentration of Roundup and an equivalent concentration of glyphosate killed 90% of the cultured cells after 18 hours' incubation. The median lethal dose for Roundup (0.7%) was nearly half that for glyphosate, meaning Roundup was nearly twice as toxic as the single chemical alone. Further, the viability of cells exposed to glyphosate was considerably reduced when even minute dilutions of Roundup were added.

After an hour's incubation with Roundup, estrogen synthesis in placental cells (as shown by aromatase activity) was enhanced by about 40%. After 18 hours, however, synthesis was inhibited, perhaps reflecting an effect on aromatase gene expression. This effect was not seen with glyphosate alone.

The study showed that the effect of Roundup on cell viability increased with time and was obtained with concentrations of the formulation 10 times lower than those recommended for agricultural use. Roundup also disrupted aromatase activity at concentrations 100 times lower than those used in agriculture. The researchers suspect that the adjuvants used in Roundup enhance the bioavailability and/or bioaccumulation of glyphosate.

How these findings translate into activity of Roundup in the human body is hard to say. The French researchers point out that serum proteins can bind to chemicals and reduce their availability-and therefore their toxicity-to cells. Nevertheless, the authors conclude that the demonstrated toxicity of Roundup, even at concentrations below those in agricultural use, could contribute to some reproduction problems.

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