Health risks associated with pesticide chlormequat on oat- and wheat-based food products require further investigation

On 15 February 2024, the New York Post published an article that claimed 80% of Americans had tested positive for the pesticide chlormequat chloride, a chemical allegedly linked to infertility and delayed puberty. U.S. presidential candidate Robert F. Kennedy, Jr. shared a link to the article on X (formerly Twitter) and claimed “Americans are being mass poisoned by agricultural chemicals and processed foods that fuel the chronic disease epidemic”.

These claims are based on a study conducted by researchers from the Environmental Working Group (EWG)^[1]. Multiple other media outlets also reported on the findings from this study.

As we will explain below, elements of this claim overstate the scientific findings of the study regarding the harmful impacts of chlormequat, leaving readers with the misleading impression that the study established chlormequat’s association with infertility and delayed puberty in humans.

Study doesn’t evaluate health risks of chlormequat

As established, the “80% of Americans” figure stems from a study published in the Journal of Exposure Science and Environmental Epidemiology on 15 February 2024. Yet the study didn’t evaluate any health risks associated with chlormequat exposure.

Instead, the study measured levels of the chemical chlormequat chloride detected in urine samples. It detected chlormequat in 77 of the 96 total samples (80% of the total samples).

The study also measured levels of chlormequat in oat and wheat products from brands including General Mills, Quaker, and 365 Whole Foods Market and found that chlormequat was detected in 26 of the 42 samples (62% of the total samples).

It’s misleading to generalize findings from 96 people to the entirety of the American public

The framing of the study—that “80% of Americans” tested positive for chlormequat—is misleading. This generalization implies that the study sampled a representative group of the American population, when in fact it measured results from just 96 individuals. For context, there are currently more than 336 million people in the U.S., according to the U.S. Census Bureau.

Further indications that the study population isn’t representative of the U.S. general population are that the ethnicity and race demographics of the sample also don’t align with U.S. population averages. Estimates from the U.S. Census Bureau indicate that White individuals make up 75% and Hispanic individuals 19% of the U.S. population.

In contrast, 44% of the study sample was categorized as White and 43% as Hispanic. Average age and sex of the total samples compared to averages of the U.S. population may have also been skewed, since 22% of the samples were taken from pregnant females between the ages of 29 and 35.

Collection methods of the urine samples varied in location, timing, and method of acquisition. Notably, these samples don’t appear to have been collected from the same individuals over time. This makes it difficult to reliably conclude that chlormequat levels in urine increased over time, as suggested by the study and reported by the New York Post. In fact, the authors of the study themselves acknowledged as much:

“Differences in chlormequat exposure in our samples could also be due to geographic locations, differing dietary patterns, or occupational exposure from uses of chlormequat in greenhouses and nurseries.”

Instead, a longitudinal study, which measures and analyzes data from the same group of individuals over an extended period of time, would provide more reliable evidence for the study’s finding that chlormequat exposure in people has risen over time.

Study provides insufficient evidence to link chlormequat in oat and wheat products to its presence in urine samples

The study measured detectable levels of chlormequat in conventional and organic oat- and wheat-based products, implying that it was the consumption of these products that led to the detection of chlormequat in the collected urine samples.

However, the oat and wheat products tested were all sourced from the Washington, D.C. metro area, whereas the urine samples were collected from Florida, Missouri, and South Carolina.

It’s certainly possible for food products to be produced in one part of the U.S. and shipped to and consumed in another. But without clear confirmation that study participants consumed these specific oat and wheat products, there’s insufficient evidence to assume a correlation between chlormequat detection in the study participants’ urine samples and the food products that tested positive for chlormequat.

It’s also misleading for media outlets to suggest that 92% of all conventional oat-based products sold in the U.S. contain chlormequat, given that the study only tested 42 products from a single geographic region. The 92% figure also refers to just under half of the total number of samples tested. In fact, when one looks at the entire number of samples tested in the study across both 2022 and 2023, detection of chlormequat drops to 62%.

And while some level of chlormequat may have been detected in these products, the U.S. Environmental Protection Agency (EPA) has yet to determine the allowable tolerance for use of chlormequat on domestic food crops.

Science Feedback reached out to the EPA regarding the EWG study. In an email, the EPA’s press office made the following statement:

“The referenced study examined the use of chlormequat on grains being imported into the U.S. Chlormequat is not currently registered for use on food in the U.S., and EPA has not yet set tolerances for the use of chlormequat on domestic food crops.”

Chlormequat levels detected in the study are within the allowable tolerance set by the EPA

Science Feedback reached out to the U.S. Food and Drug Administration (FDA) to clarify the allowable tolerance of chlormequat set by the EPA. An FDA spokesperson made the following statement via email:

“It is the responsibility of the FDA to monitor and regulate the U.S. food supply to ensure that food produced with the use of pesticides is safe to eat. For pesticide residues, we test a broad range of foods to ensure only those pesticides that are allowed by the EPA are present, and within the allowable tolerance (maximum residue level of a pesticide) that is safe. The FDA also shares public annual reports that summarize results of the FDA pesticide residue monitoring program. When new data and information emerge that raise safety concerns about the specific uses of a pesticide, the EPA may lower or revoke the tolerance altogether. 

Chlormequat chloride is currently registered for use as a plant growth regulator (PGR) by the EPA. EPA established a 40 ppm [parts per million] tolerance in oats, and the reported findings in the study are well below the tolerances established by EPA.” [emphasis added]

To clarify further, the study measured detection of chlormequat in oat and wheat products in micrograms per kilogram (µg/kg). When converting µg/kg to parts per million (ppm), this means that 1 µg/kg is equivalent to 0.001 ppm.

This means that chlormequat levels would need to be more than 40,000 µg/kg to exceed the allowable tolerance for safety set by the EPA. But the study found that the highest concentration of chlormequat detected among the oat and wheat products tested was 291 µg/kg, far below the EPA’s allowable tolerance.

Chlormequat is currently only registered for use on ornamental plants, not food crops, in the U.S.

On 21 February 2024, the New York Post published a follow-up to their article “80% of Americans tested positive for chlormequat”. This time, they claimed that the EPA is currently reviewing whether to approve the use of chlormequat on domestic crops based on the “explosive study” published by EWG researchers.

While it’s true that the EPA is currently reviewing the use of chlormequat to assist in greater yield of grain crops like oat, wheat, and barley, there’s no evidence that this review started in response to the EWG study.

In fact, the EPA’s review of chlormequat was already underway in 2023, as demonstrated by a statement released in April 2023. In the statement, the EPA explained its intention to register new uses for chlormequat chloride—specifically, to help improve yield of grain crops including oat and wheat. According to the EPA, chlormequat chloride “works to control plant size by blocking the hormones that stimulate growth prior to bloom”.

The statement also explained:

“Before issuing this proposed registration decision, EPA assessed whether exposures to this product would cause unreasonable adverse effects to human health and the environment, as required by the Federal Insecticide, Rodenticide, and Fungicide Act (FIFRA). Based on EPA’s human health risk assessment, there are no dietary, residential, or aggregate (i.e., combined dietary and residential exposures) risks of concern.”

Inconsistent findings from animal studies warrant further research on the health risks of chlormequat exposure

To date, the reproductive health risks of chlormequat have primarily been assessed via animal studies. Findings have been inconsistent.

One study of male rats found that postnatal exposure to chlormequat delayed the onset of puberty and reproductive mobility in male rats^[2]. This study seems to be the reference point for the claim that chlormequat impacts fertility and the onset of puberty.

Another study found that reproductive function among mice who ate chlormequat-treated wheat was compromised in male mice but not female mice^[3], although inconsistencies with the dosage of chlormequat administered between the two groups could potentially account for these differences.

And another study found that there was no effect on reproductive function among male and female pigs who were fed a chlormequat-treated diet^[4].

Differences in results from these animal studies warrant further investigation before any claims can reliably be made about chlormequat’s impact on reproductive health. Results from animal studies also don’t necessarily reflect what happens in humans, so further research in people is needed to determine potentially negative health impacts of chlormequat on human reproductive health.

Criticism of the EWG

For context, it’s worth noting that EWG has faced criticism for the methodology of its studies and its ties to funding from the organic food industry. In one survey administered to nearly 1,000 members of the Society of Toxicology, 79% of respondents said that environmental activist groups like EWG “overstate the health risks of chemicals”.

Conclusion

In brief, the EWG study didn’t measure health risks such as infertility or delayed puberty as a result of chlormequat consumption. The study merely measured levels of chlormequat in urine samples and oat and wheat products.

However, these results alone don’t support the implication in some news articles that chlormequat may cause infertility and delayed puberty. Further studies of human subjects are needed to determine any potentially harmful impacts of chlormequat exposure on reproductive health.

 

REFERENCES

• 1 – Temkin et al. (2024) A pilot study of chlormequat in food and urine from adults in the United States from 2017 to 2023. Journal of Exposure Science and Environmental Epidemiology.
• 2 – Hou et al. (2020) Effects of chlorocholine chloride on pubertal development and reproductive functions in male rats. Toxicology Letters.
• 3 – Sørensen and Danielsen. (2006) Effects of the plant growth regulator, chlormequat, on mammalian fertility. International Journal of Andrology.
• 4 – Sørensen et al. (2009). No effect of the plant growth regulator, chlormequat, on boar fertility. Animal.