Glyphosate: chemistry, uses and safety concerns

Chemical herbicides are widely used in food production throughout the world.

At the present time, they represent approximately 40% of chemical products sales, followed by insecticides, fungicides, and other types of pesticides.

Among these products, commercial formulations based on N-phosphonomethyl-glycine (PMG), commonly known as glyphosate, are the most used worldwide.

Such herbicidal formulations play a key role in promoting crop yields.

In Glyphosate: Chemistry, Uses and Safety Concerns review information on the presence of glyphosate-based herbicides in the environment, their potentially harmful effects, their influence on soil microbial communities and their capacity to adsorb to clay particles (which affects their environmental availability). The objective of the following work was to investigate the best way to achieve slow release of glyphosate using layered double hydroxides (LDHs) to minimize the environmental impacts of this herbicide.

LDHs are also called anionic clays because they can host negatively charged species between their layers.

They are best stabilized by anions with high charge density, such as carbonate.

Understanding the release dynamics of glyphosate in homogeneous solutions of anions that are commonly found in the soil is important, since many crops require prior soil correction, altering the pH and also the availability of anions. In one study, the chelating capacity, coordination modes and structural chemistry of glyphosate with Ni (II) cations were investigated in solution and in the solid state.

Glyphosate was purified from commercial Roundup WG (Monsanto), and characterized by 31P NMR, FTIR and melting point.

The nickel complexes were prepared from Ni(NO3)2 solutions at pH = 8.0 and 4.0, and characterized by solid-state infrared spectroscopy (4000-150 cm-1) and elemental analysis (CHN).

The solids were also studied by thermal analysis and X-ray absorption spectroscopy (XAS) using synchrotron radiation (LNLS, Brazil). Studies show that glyphosate has an oral absorption of 20 to 40% and is considered to be of low toxicity to mammals; however, recent research has shown that it can induce serious damage to mammalian cells.

The authors examine suggested mechanisms of toxicity, including the blocking of mitochondrial oxidative phosphorylation, inhibition of cytochrome p450 activity, inhibition of intestinal arylhydrocarbohydroxylase activity, changes in glucose 6-phosphate dehydrogenase activity, DNA damage, hormonal changes, channel openings of calcium, and neurotoxicity involving NMDA receptor activation. The widespread and frequent use of glyphosate has increased concern about potential adverse effects on human health.

Due to more stringent legislation on wastewater discharge and purity of drinking water, the authors discuss the development of an effective remediation technology for the decontamination of glyphosate.

Although glyphosate residues can efficiently be removed by advanced technologies, the treatments are usually expensive and difficult to maintain.

Therefore, different methods and options should be considered.