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  Dr. Elsa Nivia
Colombia Regional Coordinator,
Pesticide Action Network
,
Cali, Colombia

Effects on health and environment of glyphosate-containing herbicides  RTF

Introduction

Glyphosate is a systemic herbicide acting in a post- emergence, non-selective, broad-spectrum manner, and is used to kill undesirable plants such as annual and perennial grasses, broad -leaved plants and woody species. Glyphosate, N(-phosphonomethyl) glycine is an acid, but it is commonly applied as a salt, most often the isopropylamine salt. Its most common commercial name is Round-up. In Colombia, apart from its use as an herbicide in agriculture, it is used as a grain dessicant and as a ripening agent by aerial application and in illicit crop eradication programs - the subject of this presentation. As a crop eradication agent, glyphosate will also eradicate foodcrops and forest species, and the true impacts of its use on health and the environment have not yet been adequately studied.

The worldwide sales of glyphosate, whose main producer is Monsanto, are presently over $1,500 million annually, this is calculated to increase to $2,000 million over the next five years, equivalent to more than 40,000 the tons of the active ingredient (Dinham, 1998). At present, sales of this herbicide makeup about 40 percent of Monsanto’s agrochemical market worldwide (worldwide sales total $4,3032 million in 1998, 23.2% more than in 1997). In 1998, Monsanto held second place in the sale of agrochemicals after Novartis and first-place in the production and sale of transgenic seeds, genetically modified so that crops that are resistant to glyphosate -increasing the sales of this agrotoxin (Dinham, 1999).

Between 1986 and 1996 the use of glyphosate tripled in the US. In Europe its use increased 129% between 1991 and 1995 due to the declarations by Monsanto that the herbicide is not harmful to human beings and is environmentally safe. But, according to Cox (1995) and Dinham (1998), there are data from independent scientific investigations about glyphosate-containing herbicides, that contradict Monsanto’s statements and give a very different view of their health and environmental risks.

Before being marketed, herbicides pass through a formulation process, during which the active ingredients are mixed with other substances such as solvents, adjuvants etc, known as "inert ingredients," which are not described on the labels. In many cases, "inert ingredients" are active biologically, chemically, or are toxic, and can produce different characteristics when found in the commercial formulations, than in any of the components alone. This means that if one doesn’t make careful toxicological studies of the commercial herbicides, as used in the real world, it becomes impossible to evaluate their risks to the environment and human health.

The majority of the products that contain glyphosate are made or are used with a surfactant to aid glyphosate’s penetration into the tissues of the plant, which bestows different toxicological characteristics to the commercial formulations in comparison to glyphosate alone. In the case of Roundup, the herbicidal formulation most used, it contains a surfactant called polyoxyethylamine (POEA), organic acids related to glyphosate, isopropylamine, and water. In the present study we will make examine to the characteristics of glyphosate, but separately the scientific studies made with Round-up.

Commercial Names

In Colombia, Monsanto has registered glyphosate (ICA 1998) under the commercial names Roundup, Rocket, Rocky, Faena, Patrol, Squadron, Ranger and Fuete. Other agrochemical businesses alsohave registered commercial formulations based on the same active ingredient, under the names of: Batalla (Bayer); Glyfoagri (Disagri); Socar (Agrevo); Crossout, Candela y Glyfosan (Agroser); Glifonox (Crystal); Glifosol (Coljap); Stelar (Dow); Panzer (Invequímica); Glyphogan (Magan); Faena (Proficol); Regio (Quimor); Sunup (Sundat); Glifosato Agrogen (Agroquímicos del Cauca) y Tunda (Fertilizantes Cafeteros).

Mode of Action

The herbicidal action of glyphosate is probably due to the inhibition of the biosynthesis of aromatic amino acids (phenylalanine, tyrosine, and tryptophan), used for the synthesis of proteins essential for the growth and survival of most plants. Glyphosate inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, important for the synthesis of aromatic amino acids; and it may also inhibit or repress the activity of other enzymes, chlorismate mutase and prephrenate hydratase, both involved in other steps of the synthesis of those same aminoacids. All of these enzymes are part of the shikimic acid pathway, present in higher plants and microorganisms but not in animals.

Glyphosate can affect enzymes not connected with the shikimic acid pathway. In sugar cane, it lowers the activity of one of the enzymes involved in sugar metabolism, acid invertase. This reduction appears to be mediated by auxins (plant hormones).

Glyphosate also affects animal and human enzyme systems. In rats, injection into the abdomen decreases the activity of two detoxification enzymes, cytochrome P-450 and a monooxygenase, and decreases the intestinal activity of the enzyme aryl hydrocarbon hydroxylase (Cox 1995).

New More Toxic Formulations of Glyphosate

Research: According to greenhouse investigations in Maryland, USA and field investigations between 1995 and 1997 in Hawaii, with the addition of two surfactants, AL-77 and Optima to the glyphosate in the Rodeo formulation, the toxicity of glyphosate against coca was increased by a factor of four, compared to the commercial Roundup formula (Collins & Helling). According to this study, the herbicide mixture presently used in Colombia for coca eradication has been "modified", with excellent results.

This supposed change of formulation coincides with complaints from the affected communities, who claim that more damage is being done to grasses and food crops, and that the symptoms of the resultant intoxication are more serious. We do not know exactly what formulation is being used. The two new surfactants are made up of the following:

A77: 1:1 mixture (by volume) of Agridex and Silwet L-77.

Agri-Dex: a mixture of heavy-range paraffin-based petroleum oil.


Posted by Roger Lovejoy on 30 December, 2001
extracted from www.usfumigation.org/NovPressConfSpeakers/ElsaNivia/ElsaNivia.htm