Researchers are advancing efforts to accurately measure the glyphosate pesticide in...

Pesticides help farmers increase food production, reduce costly damage to crops, and even prevent the spread of insect-borne diseases. However, since the chemicals can also get into human food, it is important to ensure that they are safe. A commonly used pesticide known as glyphosate has raised concerns about food safety, as well as the safety of one of its by-products, AMPA. Researchers at the National Institute for Standards and Technology (NIST) are advancing their efforts to accurately measure glyphosate and AMPA in oat-based foods, where they often appear through the development of reference materials.

The Environmental Protection Agency (EPA) sets tolerances for pesticide levels in food that are still considered safe for consumption. Food manufacturers test their products to make sure they meet EPA regulations. However, to make sure their measurements are accurate, they need a reference material (RM) with known glyphosate levels to compare their products to.

No reference material is available to measure glyphosate, the active ingredient in Roundup, in oatmeal or oat-based products in which the pesticide is commonly used. However, there are a small number of food-based RMs available for measuring other pesticides. In an effort to develop one for glyphosate and meet the immediate needs of manufacturers, NIST researchers optimized a test method to analyze glyphosate in 13 commercially available oat-based food samples to identify possible reference materials. They found glyphosate in all samples and found AMPA (short for aminomethylphosphonic acid) in three samples.

The researchers published their results in the journal Food chemistry.

Glyphosate has been one of the most dominant pesticides in the US and around the world for decades. In 2014 alone, according to a 2016 study, 125,384 tons of glyphosate were used in the US. It is a herbicide, a type of pesticide used to destroy weeds or unwanted plants that are harmful to crops.

Sometimes pesticides remain on food in small amounts called residues. In the case of glyphosate, it can also break down into AMPA, which can also remain on fruits, vegetables, and grains. The potential effects of AMPA on human health are not fully understood and remain an active area of ​​study. Glyphosate is also commonly used for other grains and grains such as barley and wheat, but oats are a special case.

“Oats are unique when it comes to grain,” said NIST researcher Jacolin Murray. “We chose oats as the first material because food manufacturers use the glyphosate as a desiccant to dry out the crop before harvest. Oats are usually high in glyphosate. ”The drying out of the plants enables earlier harvest and improves the evenness of the plants. Because of its widespread use, glyphosate is typically found in higher concentrations compared to other pesticides, according to co-author Justine Cruz.

The 13 oat samples in the study comprised oatmeal, light to highly processed oat-based breakfast cereals and oatmeal from conventional and organic farming methods.

Researchers analyzed the samples for glyphosate and AMPA using a modified method of extracting glyphosate from solid foods in conjunction with standard techniques known as liquid chromatography and mass spectrometry. The first method involves dissolving the solid sample in a liquid mixture that removes glyphosate from the food. Next, in liquid chromatography, the glyphosate and AMPA in the extract sample are separated from other components in the sample. Finally, mass spectrometry measures the mass-to-charge ratio of ions to identify the various chemical compounds in the sample.

Their results showed that the lowest glyphosate levels were detected in the organic breakfast cereal sample (26 nanograms per gram) and the organic oatmeal sample (11 nanograms per gram). The highest glyphosate levels (1,100 nanograms per gram) were detected in conventional instant oatmeal samples. AMPA levels were much lower than glyphosate levels in both organic and conventional oatmeal and oat samples.

All glyphosate and AMPA levels in oatmeal and oat-based cereals were well below the EPA tolerance of 30 micrograms per gram. “The highest glyphosate levels we measured were 30 times below the legal limit,” said Murray.

Based on the results of this study and initial discussions with stakeholders interested in using an RM on oatmeal and oat-based grains, the researchers determined that having a low-grade (50 nanograms per gram) and RM could be beneficial develop a high level one (500 nanograms per gram). These RMs would be beneficial to agriculture and food testing laboratories, as well as food manufacturers who need to test their feedstock for pesticide residues and have an accurate standard against which to compare their measurements.

NIST’s RMs are used not only in the United States but also worldwide. It was therefore important for researchers to also take into account the legal limit values ​​abroad, for example in Europe, where the limit value is 20 micrograms per gram.

“Our researchers need to balance the needs of food testing laboratories in the US and beyond to produce reference materials with global reach,” said NIST researcher Katrice Lippa.

The researchers identified three potential RM candidates for glyphosate in oat-based cereals and two candidates for AMPA. They were also able to conduct a preliminary stability study that showed that glyphosate in oats was stable for a period of six months at a constant temperature of 40 degrees Celsius, which is important for the development of a future RM, which could possibly be based on one or more of these products.

Next, the researchers plan to evaluate the feasibility of the RMs through an interlaboratory study and then conduct further long-term stability studies of both glyphosate and AMPA in their materials. The NIST team will continue to involve stakeholders to ensure that the RM meets their needs.

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More information:
Justine M. Cruz et al., Determination of Glyphosate and AMPA in Oat Products for Selection of Reference Materials, Food chemistry (2020). DOI: 10.1016 / j.foodchem.2020.128213

Provided by the National Institute of Standards and Technology