HomeSafetyChlormequat, the pesticide that threatens fertility. EWG study

Chlormequat, the pesticide that threatens fertility. EWG study

The pesticide chlormequat, toxic to fertility and development in animals, was detected for the first time in the urine of 80% of people tested in the United States, where it is less widespread than in Europe. The alarming discovery is described in the peer-reviewed scientific study (Temkin et al., 2024) by the EWG (Environmental Working Group) published in the Journal of Exposure Science & Environmental Epidemiology. (1)

Chlormequat, the molecule that attacks fertility

Chlormequat was first registered in the United States in 1962 as a plant growth regulator. It works by reducing the height of the stem, thus decreasing the likelihood of crops bending and complicating harvesting.

The toxicity of this molecule on development, reproduction and the endocrine system emerged at the beginning of the 80s of the last century. Danish pig farmers observed reproductive decline in animals raised on chlormequat-treated grains. Since then, numerous studies have confirmed and expanded the initial evidence on reduced fertility (of males and females) and damage to the fetus. The fear is that the effects observed on animals also apply to humans.

Exposure of the population, in Europe and the USA

In the European Union chlormequat:

– is authorized on 'conventional' (i.e. non-organic) crops of soft wheat, durum wheat, rye, oats, barley

– can remain in non-organically cultivated mushrooms, due to contamination of the straw (treated with chlormequat) used as a substrate

– is also used on ornamental and flowering plants (poinsettia, geranium, begonia, chrysanthemum, etc.).

In the United States, however, the use of chlormequat is authorized only on ornamental plants. But the agrotoxic reaches consumers through food, cereals (in primis), imported mainly from Canada.

The customs clearance of chlormequat in the USA

The green light to the import into the USA of oats and wheat treated with chlormequat was decided in 2018 by the EPA, the Environmental Protection Agency, under President Trump. The same administration then granted, in 2020, an increase in the permitted contamination threshold.

Under the Biden presidency it didn't get any better. 'In April 2023, in response to a 2019 application submitted by chlormequat producer Taminco, the Biden EPA proposed to allow the first-ever use of chlormequat on barley, oats, triticale, and wheat grown in the United States', reports EWG, which is fighting against this eventuality. (3)

The impact on the population

The gradual customs clearance of chlormequat in the United States goes hand in hand with the increase in levels of human contamination detected in recent biomonitoring of the general population, the researchers explain.

For the study , in fact, the EWG compared urine samples collected between 2017 and 2023 from 96 people living in different areas in the United States.

4 out of 5 individuals tested positive

'The chemical substance was detected in four out of five people tested – 77 out of 96 – showing that exposure to chlormequat is likely widespread. These results also suggest regular exposure, as we know that chlormequat leaves the body in about 24 hours' reports EWG.

The tests also show a progressive increase in concentrations detected in the urine:

– from 0,22 to 5,4 µg of chlormequat per g of creatinine in 2017,

– from 0,11 to 4,3 in 2018-2022,

– from 0,27 to 52,8 in 2023.

Chlormequat in foods

Between the two cereals of imports responsible for the exposure of the US population to chlormequat, oats are far more involved.

Analyzes on food samples purchased in the United States by EWG in 2022 and 2023 show

– detectable levels of chlormequat in all but two of 25 conventional oat products, with concentrations up to 291 µg/kg,

– only one case of slight positivity to chlormequat (17 µg/kg) among the eight organic oat-based products analysed,

– the presence of low concentrations of chlormequat in two of the nine wheat-based products tested (3,5 and 12,6 µg/kg).

More extensive biomonitoring is needed

In light of the data emerged in recent years on population contamination and in the presence of clear political openings to the use of chlormequat in the United States, EWG calls on the federal government to initiate extensive biomonitoring campaigns and systematic food analysis to ascertain the extent of yet another threat to Health.

And he warns that 'until the government fully protects consumers, it can reduce exposure to chlormequat by choosing organic products, grown without synthetic pesticides such as chlormequat'.

European and British consumers more at risk

The same advice is even more true for Europeans, who are more exposed to chlormequat, as demonstrated by the limited biomonitoring conducted so far:

– analyzes on over 1.000 Swedish adolescents revealed a 100% incidence of positivity to the molecule, with concentrations decreasing from 2,7 µg of chlormequat per g of creatinine in 2009 to 0,86 µg in 2017,

– tests conducted in the United Kingdom, from 2011 to 2012, on 140 adults and children living less than 100 meters from agricultural fields sprayed with pesticides showed average concentrations of 15,1 μg/g of creatinine, with levels unrelated to events of spreading of pesticides. (4)

Bread in the UK

Food analyses conducted in the UK in 2022, moreover, show significant contamination by chlormequat:

– in 90% of wheat-based products, such as bread, at an average concentration of 60 ppb,

– in 82% of oat samples with average concentrations of 1650 ppb, more than 15 times higher than US samples. (5)

In the United Kingdom and the European Union, chlormequat is often the most detected pesticide residue in cereals, as documented by monitoring investigations lasting several years, recall the EWA researchers. (6) A record that can add to the enormous number of threats to human fertility and reproduction.

The large agricultural confederations in the European Union (Coldiretti (in primis)), meanwhile, congratulate themselves on having successfully boycotted the proposed SUR (Sustainable Use and Reduction of Pesticides) regulation. (7)

Marta Strinati


(1) Temkin, A.M., Evans, S., Spyropoulos, D.D. et al. A pilot study of chlormequat in food and urine from adults in the United States from 2017 to 2023. J Expo Sci Environ Epidemiol (2024).

(2) Reg. (EU) 2017/693

(3) Anthony Lacey, Alexis Temkin. EWG finds little-known toxic chemical in four out of five people tested. EWG. 15.2.24

(4) Galea KS, MacCalman L, Jones K, Cocker J, Teedon P, Cherrie JW, van Tongeren M. Urinary biomarker concentrations of captan, chlormequat, chlorpyrifos and cypermethrin in UK adults and children living near agricultural land. J Expo Sci Environ Epidemiol. 2015 Nov-Dec;25(6):623-31. doi: 10.1038/jes.2015.54. Epub 2015 Sep 16. PMID: 26374656; PMCID: PMC4611359.

(5) Source: Department for Environment FaRA. Quarter 3 2022 PRIF Report Quartlery Data. United Kingdom Department for Environment Food & Rural Affairs2023. See note 20 of the study indicated in note (1)

(6) See EFSA. The 2014 European Union report on pesticide residues in food. EFSA J. 2016;14:4611

(7) Dario Dongo. Protesting farmers, pesticides instead of #fairprice. GIFT (Great Italian Food Trade).

Marta Strinati
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Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".

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