Glyphosate is an organophosphate compound – an aminophosphonic analogue of the natural amino acid glycine – that acts as a broad-spectrum systemic herbicide and crop desiccant. Glyphosate interferes with a metabolic pathway found only in plants and microorganisms; this pathway does not exist in mammals including humans.
Glyphosate is absorbed through foliage, and minimally through roots, and transported to growing points. Therefore, it is effective only on actively growing plants and is not effective as a preemergent herbicide.
Its main use is to kill weeds, especially broadleaf weeds and grasses that compete with crops. It was brought to market for agricultural use in 1974. Additionally, an increasing number of crops have been genetically engineered to be tolerant of glyphosate which allows farmers to use glyphosate as a post- emergence herbicide against weeds. A third commonly practiced use for glyphosate is for crop desiccation, a practice shown to increase harvest yield and uniformity. Though not a desiccant, glyphosate application just before harvest kills the crop plants so that the food crop dries from environmental conditions more quickly and evenly.
Glyphosate has been shown to have a half-life in soil that ranges between 2 and 197 days; a typical field half-life of 47 days is generally accepted. Glyphosate is readily degraded by soil microbes to aminomethlyphosphonic acid (AMPA), its main metabolic residue, and N-acetyl-AMPA. Metabolism studies in several genetically modified crops however have demonstrated the presence of N-acetylglyphosate, a new metabolite that is not observed in conventional crops.
In the United States, the US Environmental Protection Agency and the US Food and Drug Administration are responsible for the establishment of such MRLs for glyphosate in defined agricultural products and regulatory testing, respectively. In the EU, regulation of glyphosate is based on MRLs proposed by the European Food Safety Authority (EFSA). Significant differences in MRLs established by EFSA and the US EPA exist for a wide range of agricultural commodities and the analytical testing standards (e.g. Limit of Detection and Limit of Quantitation) used to measure glyphosate residues. These differences and analytical gaps in testing methodology have created confusion for many agribusinesses and food producers and has impacted the validity of current risk assessment data.
A Reasoned Opinion recently adopted by EFSA that proposed MRLs for total glyphosate (based on previously established residue definitions) for regulatory enforcement and risk assessment for all plants and plant commodities noted significant analytical testing needs. It was particularly noteworthy that “fully validated analytical methods for enforcement of glyphosate and glyphosate residues in complex matrices (relevant for the authorization on conventional tea, coffee beans, carobs, hops, spices and herbal infusion) are missing and are still required”. Genetically engineered crops and products are included in this finding as well.
AOAC is proposing the establishment of a working group to develop a voluntary consensus standard (or standards) for the simultaneous determination of glyphosate (including glyphosate trimesium) and its metabolites: N-acetylglyphosate, aminomethylphosponic acid (AMPA), and N-acetyl-aminophosphonic acid (N-acetyl AMPA) in the following:
The Working Group will develop one or more (as deemed necessary by WG experts) Standard Method Performance Requirements, SMPRs® for the determination – simultaneous or otherwise – of glyphosate (including glyphosate trimesium) and its metabolites: N-acetylglyphosate, aminomethylphosponic acid (AMPA), and N-acetyl-aminophosphonic acid (N-acetyl AMPA) in the above-identified agricultural products and consumer commodities.
†Priority GMO matrices include cereals (especially corn) and pulses (especially soy). Additional GMO matrices to be assessed under this agreement will be determined in consultation with Advisory Panel Members.
‡Due to the recognized disparity in international regulations, the inclusion of GMO metabolites in non-GMO crops still would be needed.
The Glyphosate Advisory Panel will be comprised of funding organizations to determine initial priorities and working group strategies. This panel will meet quarterly to review progress and consider additional objectives as a result of working group accomplishments. The projected funding level needed to complete this initiative as described is $70,000. We are asking organizations to join this important project for a contribution of $10,000. Other levels of contributions will be considered as well.*
*AOAC INTERNATIONAL will continue to explore a multi-tiered funding schedule to avoid any unintended barrier to the ultimate success of this project and to encourage as many stakeholders to get involved as possible.
Palmer A. Orlandi, Jr., Ph. D.
Chief Science Officer, AOAC INTERNATIONAL
2275 Research Blvd., Suite 300
Rockville, MD 20850
Tel: 301-924-7077; ext. 163
[email protected] www.aoac.org
