APA RESEARCH PAPER

APA Research Paper

Glyphosate and effects

Introduction

Glyphosate (N-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide used to kill weeds, especially annual broadleaf weeds and grasses known to compete with commercial crops grown around the globe. It was discovered to be a herbicide byMonsanto chemist John E. Franz in 1970.[3] Monsanto brought it to market in the 1970s under the trade name Roundup, and Monsanto's last commercially relevant United States patent expired in 2000.

Discussion

Called by experts in herbicides "virtually ideal" due to its broad spectrum and low toxicity compared with other herbicides,[4] glyphosate was quickly adopted by farmers. Use increased even more when Monsanto introduced glyphosate-resistant crops, enabling farmers to kill weeds without killing their crops. In 2007 glyphosate was the most used herbicide in the United States agricultural sector, with 180 to 185 million pounds (82,000 to 84,000 tonnes) applied, and the second most used in home and garden market where users applied 5 to 8 million pounds (2,300 to 3,600 tonnes); additionally industry, commerce and government applied 13 to 15 million pounds (5,900 to 6,800 tonnes).[5] While glyphosate has been approved by regulatory bodies worldwide and is widely used, concerns about its effects on humans and the environment persist.[6]

Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the aromatic amino acids: tyrosine, tryptophan andphenylalanine. It is absorbed through foliage and translocated to growing points. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide.

Some crops have been genetically engineered to be resistant to it (i.e. Roundup Ready, also created by Monsanto Company). Such crops allow farmers to use glyphosate as a post-emergence herbicide against both broadleaf and cereal weeds, but the development of similar resistance in some weed species is emerging as a costly problem. Soy was the first Roundup Ready crop.

Effects on fish and amphibians

glyphosate is generally less persistent in water than in soil, with 12 to 60 day persistence observed in Canadian pond water, yet because glyphosate binds to soil, persistence of over a year have been observed in the sediments of ponds in Michigan and Oregon.[46] In streams, maximum glyphosate concentrations were measured immediately post-treatment and dissipated rapidly.[46] Glyphosate is "practically nontoxic to slightly toxic" for amphibians and fish.[49]

Soil degradation, and effects on micro-organism and worms

When glyphosate comes into contact with the soil, it can be rapidly bound to soil particles and be inactivated.[46][50] Unbound glyphosate can be degraded by bacteria.[51]

In soils, half-lives vary from as little as three days at a site in Texas to 141 days at a site in Iowa.[50] In addition, the glyphosate metabolite aminomethylphosphonic acid has been found in Swedish forest soils up to two years after a glyphosate application.[52]Glyphosate adsorption to soil varies depending on the kind of soil.[53]

It has been suggested that glyphosate can harm the bacterial ecology of soil and cause micronutrient deficiencies in plants,[54] includingnitrogen-fixing bacteria.[55]

Other mammals

A review of the ecotoxicological data on Roundup shows there are at least 58 studies of the effects of Roundup itself on a range of organisms.[49] This review concluded that "for terrestrial uses of Roundup minimal acute and chronic risk was predicted for potentially exposed non-target ...