Chlormequat is on the rise in the US population

Chlormequat chloride, a chemical used to stunt the growth of some ornamental plants and grains, is increasingly showing up in the US population, according to a report from the Environmental Working Group (EWG), an advocacy organization (DOI: 10.1038/s41370-024-00643-4).

The EWG commissioned a UK-based laboratory to quantify chlormequat in a few dozen urine samples collected from volunteers in the US. The samples were collected in 2017, 2018–2022, and 2023, from different groups of volunteers each time. The group also hired a California-based lab to quantify chlormequat in cereals and granola bars purchased from stores in the Washington, DC, area in 2022 and 2023.

Urine samples collected in 2023 had markedly higher levels of chlormequat than those from 2017 to 2022, the EWG says. Even so, the levels were several orders of magnitude below acceptable limits established by the US Environmental Protection Agency and the European Food Safety Authority. The EWG says reevaluation of those safety thresholds may be warranted in light of new toxicological studies.

“The ubiquity of this little-studied pesticide in people raises alarm bells about how it could potentially cause harm without anyone even knowing they’ve consumed it,” Alexis Temkin, an EWG toxicologist and lead author of the study, says in a statement. The chemical has been linked to reproductive and developmental effects in animal studies.

The EWG attributes the rise in chlormequat levels in the US population to the EPA’s move in 2018 to allow chlormequat on imported oats, wheat, and barley, and its decision in 2020 to increase how much is allowed on imported oats.

The group’s analysis in 2022 and 2023 of chlormequat in foods revealed that the chemical is present at levels above 100 ppb in several oat-based products, including old-fashioned oats and popular cereals.

The EWG says it is concerned that the amount of chlormequat in food, and in people who eat that food, will rise if the EPA follows through with a proposal announced last year that would allow chlormequat on barley, oat, triticale, and wheat grown in the US. The National Association of Wheat Growers and the National Barley Growers Association are urging the EPA to finalize the proposal in time for the 2024 growing season.