Chlormequat is a plant growth regulator whose use in cereal crops is increasing in North America. Toxicology studies have shown that exposure to chlormequat may reduce fertility and cause harm to the developing fetus at doses below the permitted daily dose established by regulatory authorities. Here, we report the presence of chlormequat in urine samples collected from the US population, with detection rates of 69%, 74%, and 90% in samples collected in 2017, 2018–2022, and 2023, respectively. From 2017 to 2022, low concentrations of chlormequat were detected in samples, and from 2023, chlormequat concentrations in samples increased significantly. We also noticed that chlormequat was found more frequently in oat products. These results and the toxicity data for chlormequat raise concerns about current exposure levels and call for more extensive toxicity testing, food surveillance, and epidemiological studies to assess the impact of chlormequat exposure on human health.
This study reports the first detection of chlormequat, an agrochemical with developmental and reproductive toxicity, in the US population and in the US food supply. While similar levels of the chemical were found in urine samples from 2017 to 2022, significantly elevated levels were found in the 2023 sample. This work highlights the need for broader monitoring of chlormequat in food and human samples in the United States, as well as toxicology and toxicology. Epidemiological studies of chlormequat, as this chemical is an emerging contaminant with documented adverse health effects at low doses in animal studies.
Chlormequat is an agricultural chemical first registered in the United States in 1962 as a plant growth regulator. Although currently only permitted for use on ornamental plants in the United States, a 2018 U.S. Environmental Protection Agency (EPA) decision allowed the import of food products (mostly grains) treated with chlormequat [1]. In the EU, UK and Canada, chlormequat is approved for use on food crops, mainly wheat, oats and barley. Chlormequat can reduce the height of the stem, thereby reducing the likelihood of the crop becoming twisted, making harvesting difficult. In the UK and EU, chlormequat is generally the most detected pesticide residue in cereals and cereals, as documented in long-term monitoring studies [2, 3].
Although chlormequat is approved for use on crops in parts of Europe and North America, it exhibits toxicological properties based on historical and recently published experimental animal studies. The effects of chlormequat exposure on reproductive toxicity and fertility were first described in the early 1980s by Danish pig farmers who observed decreased reproductive performance in pigs raised on chlormequat-treated grain . These observations were later examined in controlled laboratory experiments in pigs and mice, in which female pigs fed chlormequat-treated grain exhibited disturbances in estrous cycles and mating compared with control animals fed a diet without chlormequat. Additionally, male mice exposed to chlormequat through food or drinking water during development showed decreased ability to fertilize sperm in vitro . Recent reproductive toxicity studies of chlormequat have shown that exposure of rats to chlormequat during sensitive periods of development, including pregnancy and early life, resulted in delayed puberty, decreased sperm motility, decreased male reproductive organ weight, and decreased testosterone levels. Developmental toxicity studies also indicate that exposure to chlormequat during pregnancy may cause fetal growth and metabolic abnormalities . Other studies have found no effect of chlormequat on reproductive function in female mice and male pigs, and no subsequent studies have found an effect of chlormequat on the fertility of male mice exposed to chlormequat during development and postnatal life . Equivocal data on chlormequat in the toxicological literature may be due to differences in test doses and measurements, as well as the choice of model organisms and sex of experimental animals. Therefore, further investigation is warranted.
Although recent toxicological studies have shown effects of chlormequat on development, reproduction and the endocrine system, the mechanisms by which these toxicological effects occur are unknown. Some studies suggest that chlormequat may not act through well-defined mechanisms of endocrine-disrupting chemicals, including estrogen or androgen receptors, and does not alter aromatase activity . Other evidence suggests that chlormequat may cause side effects by altering steroid biosynthesis and causing endoplasmic reticulum stress.
Although chlormequat is ubiquitously present in common European foods, the number of biomonitoring studies assessing human exposure to chlormequat is relatively small. Chlormequat has a short half-life in the body, approximately 2–3 hours, and in studies involving human volunteers, most experimental doses were cleared from the body within 24 hours . In general population samples from the UK and Sweden, chlormequat was detected in the urine of almost 100% of study participants at significantly higher frequencies and concentrations than other pesticides such as chlorpyrifos, pyrethroids, thiabendazole and mancozeb metabolites. Studies in pigs have shown that chlormequat can also be found in serum and may be transferred into milk, but these matrices have not been studied in humans or other experimental animal models, although its presence in serum and milk may be associated with reproductive harm from the chemicals. . There are important effects of exposure during pregnancy and in infants .
In April 2018, the U.S. Environmental Protection Agency announced acceptable food tolerance levels for chlormequat in imported oats, wheat, barley, and certain animal products, allowing chlormequat to be imported into the U.S. food supply. The allowable oat content was subsequently increased in 2020. To characterize the impact of these decisions on the occurrence and prevalence of chlormequat in the US adult population, this pilot study measured the amount of chlormequat in the urine of people from three US geographic regions from 2017 to 2023 and again in 2022. and chlormequat content of oat and wheat products purchased in the United States in 2023.
Samples collected in three geographic regions between 2017 and 2023 were used to measure urinary levels of chlormequat in US residents. Twenty-one urine samples were collected from deidentified pregnant women who consented at the time of delivery according to a 2017 Institutional Review Board (IRB)-approved protocol from the Medical University of South Carolina (MUSC, Charleston, SC, USA). Samples were stored at 4°C for up to 4 hours, then aliquoted and frozen at -80°C. Twenty-five adult urine samples were purchased from Lee Biosolutions, Inc (Maryland Heights, MO, USA) in November 2022, representing a single sample collected from October 2017 to September 2022, and were collected from volunteers (13 men and 12 women). ) on loan to the Maryland Heights, Missouri collection. Samples were stored at -20°C immediately after collection. In addition, 50 urine samples collected from Florida volunteers (25 men, 25 women) in June 2023 were purchased from BioIVT, LLC (Westbury, NY, USA). Samples were stored at 4°C until all samples were collected, then aliquoted and frozen at -20°C. The supplier company obtained the necessary IRB approval to process human samples and consent to sample collection. No personal information was provided in any of the samples tested. All samples were sent frozen for analysis. Detailed sample information can be found in Supporting Information Table S1.
Quantification of chlormequat in human urine samples was determined by LC-MS/MS at the HSE Research Laboratory (Buxton, UK) according to the method published by Lindh et al. Slightly modified in 2011 . Briefly, samples were prepared by mixing 200 μl of unfiltered urine with 1.8 ml of 0.01 M ammonium acetate containing internal standard. The sample was then extracted using an HCX-Q column, conditioned first with methanol, then with 0.01 M ammonium acetate, washed with 0.01 M ammonium acetate, and eluted with 1% formic acid in methanol. Samples were then loaded onto a C18 LC column (Synergi 4 µ Hydro-RP 150 × 2 mm; Phenomenex, UK) and separated using an isocratic mobile phase consisting of 0.1% formic acid:methanol 80:20 at flow rate 0.2. ml/min. Reaction transitions selected by mass spectrometry were described by Lindh et al. 2011. The detection limit was 0.1 μg/L as reported in other studies .
Urinary chlormequat concentrations are expressed as μmol chlormequat/mol creatinine and converted to μg chlormequat/g creatinine as reported in previous studies (multiply by 1.08).
Anresco Laboratories, LLC tested food samples of oats (25 conventional and 8 organic) and wheat (9 conventional) for chlormequat (San Francisco, CA, USA). Samples were analyzed with modifications according to published methods [19]. LOD/LOQ for oat samples in 2022 and for all wheat and oat samples in 2023 were set at 10/100 ppb and 3/40 ppb, respectively. Detailed sample information can be found in Supporting Information Table S2.
Urinary chlormequat concentrations were grouped by geographic location and year of collection, with the exception of two samples collected in 2017 from Maryland Heights, Missouri, which were grouped with other 2017 samples from Charleston, South Carolina. Samples below the detection limit of chlormequat were treated as percent detection divided by the square root of 2. Data were not normally distributed, so the nonparametric Kruskal-Wallis test and Dunn’s multiple comparison test were used to compare medians between groups. All calculations were performed in GraphPad Prism (Boston, MA).
Chlormequat was detected in 77 of 96 urine samples, representing 80% of all urine samples. Compared to 2017 and 2018–2022, 2023 samples were detected more frequently: 16 out of 23 samples (or 69%) and 17 out of 23 samples (or 74%), respectively, and 45 out of 50 samples (i.e. 90%). ) were tested (Table 1). Prior to 2023, chlormequat concentrations detected in the two groups were equivalent, whereas chlormequat concentrations detected in the 2023 samples were significantly higher than in samples from previous years (Figure 1A,B). The detectable concentration ranges for the 2017, 2018–2022, and 2023 samples were 0.22 to 5.4, 0.11 to 4.3, and 0.27 to 52.8 micrograms of chlormequat per gram of creatinine, respectively. The median values for all samples in 2017, 2018–2022, and 2023 are 0.46, 0.30, and 1.4, respectively . These data suggest that exposure may continue given the short half-life of chlormequat in the body, with lower exposure levels between 2017 and 2022 and higher exposure levels in 2023.
The chlormequat concentration for each individual urine sample is presented as a single point with bars above the mean and error bars representing +/- standard error. Urinary chlormequat concentrations are expressed in mcg of chlormequat per gram of creatinine on a linear scale and a logarithmic scale . Nonparametric Kruskal-Wallis analysis of variance with Dunn’s multiple comparison test was used to test statistical significance .
Food samples purchased in the United States in 2022 and 2023 showed detectable levels of chlormequat in all but two of 25 traditional oat products, with concentrations ranging from undetectable to 291 μg/kg, indicating chlormequat in oats. The prevalence of vegetarianism is high. Samples collected in 2022 and 2023 had similar average levels: 90 µg/kg and 114 µg/kg, respectively. Only one sample of eight organic oat products had a detectable chlormequat content of 17 µg/kg. We also observed lower concentrations of chlormequat in two of the nine wheat products tested: 3.5 and 12.6 μg/kg, respectively .
This is the first report of the measurement of urinary chlormequat in adults living in the United States and in populations outside the United Kingdom and Sweden. Pesticide biomonitoring trends among more than 1,000 adolescents in Sweden recorded a 100% detection rate for chlormequat from 2000 to 2017. The average concentration in 2017 was 0.86 micrograms of chlormequat per gram of creatinine and appears to have decreased over time, with the highest average level being 2.77 in 2009 . In the UK, biomonitoring found a much higher average chlormequat concentration of 15.1 micrograms of chlormequat per gram of creatinine between 2011 and 2012, although these samples were collected from people living in agricultural areas. there was no difference in exposure. Spray incident[15]. Our study of the US sample from 2017 to 2022 found lower median levels compared to previous studies in Europe, while in the 2023 sample median levels were comparable to the Swedish sample but lower than the UK sample .
These differences in exposure between regions and time points may reflect differences in agricultural practices and regulatory status of chlormequat, which ultimately influence the levels of chlormequat in food products. For example, chlormequat concentrations in urine samples were significantly higher in 2023 compared to previous years, which may reflect changes related to EPA regulatory actions related to chlormequat (including chlormequat food limits in 2018). US food supplies in the near future. Raise oat consumption standards by 2020. These actions allow the import and sale of agricultural products treated with chlormequat, for example, from Canada. The lag between EPA regulatory changes and the elevated concentrations of chlormequat found in urine samples in 2023 can be explained by a number of circumstances, such as delays in the adoption of agricultural practices that use chlormequat, delays by U.S. companies in negotiating trade agreements, and private individuals. are experiencing delays in purchasing oats due to depletion of old product stocks and/or due to longer shelf life of oat products.
To determine whether the concentrations observed in US urine samples reflect potential dietary exposure to chlormequat, we measured chlormequat in oat and wheat products purchased in the US in 2022 and 2023. Oat products contain chlormequat more often than wheat products, and the amount of chlormequat in different oat products varies, with an average level of 104 ppb, possibly due to supply from the United States and Canada, which may reflect differences in use or disuse. between products produced from oats treated with chlormequat. In contrast, in UK food samples, chlormequat is more abundant in wheat-based products such as bread, with chlormequat detected in 90% of samples collected in the UK between July and September 2022. The average concentration is 60 ppb. Similarly, chlormequat was also detected in 82% of UK oat samples at an average concentration of 1650 ppb, more than 15 times higher than in US samples, which may explain the higher urinary concentrations observed in UK samples .
Our biomonitoring results indicate that exposure to chlormequat occurred prior to 2018, although dietary tolerance to chlormequat has not been established. Although chlormequat is not controlled in foods in the United States, and there are no historical data on the concentrations of chlormequat in foods sold in the United States, given the short half-life of chlormequat, we suspect that this exposure may be dietary. Additionally, choline precursors in wheat products and egg powders naturally form chlormequat at high temperatures, such as those used in food processing and manufacturing, resulting in chlormequat concentrations ranging from 5 to 40 ng/g. Our food testing results indicate that some samples, including the organic oat product, contained chlormequat at levels similar to those reported in studies of naturally occurring chlormequat, while many other samples contained higher levels of chlormequat. Thus, the levels we observed in urine through 2023 were likely due to dietary exposure to chlormequat generated during food processing and manufacturing. Observed levels in 2023 are likely due to dietary exposure to spontaneously produced chlormequat and imported products treated with chlormequat in agriculture. Differences in chlormequat exposure among our samples may also be due to geographic location, different dietary patterns, or occupational exposure to chlormequat when used in greenhouses and nurseries.
Our study suggests that larger sample sizes and a more diverse sample of chlormequat-treated foods are needed to fully evaluate potential dietary sources of chlormequat in low-exposure individuals. Future studies including analysis of historical urine and food samples, dietary and occupational questionnaires, ongoing monitoring of chlormequat in conventional and organic foods in the United States, and biomonitoring samples will help elucidate common factors of chlormequat exposure in the US population.
The likelihood of increased levels of chlormequat in urine and food samples in the United States in the coming years remains to be determined. In the United States, chlormequat is currently only allowed in imported oat and wheat products, but the Environmental Protection Agency is currently considering its agricultural use in domestic non-organic crops. If such domestic use is approved in conjunction with the widespread agricultural practice of chlormequat abroad and domestically, levels of chlormequat in oats, wheat, and other grain products could continue to rise, leading to higher levels of chlormequat exposure. Total US population.
Current urinary concentrations of chlormequat in this and other studies indicate that individual sample donors were exposed to chlormequat at levels that were both below the published US Environmental Protection Agency reference dose (RfD) (0.05 mg/kg body weight per day), so are acceptable. The daily intake is several orders of magnitude lower than the intake value published by the European Food Safety Authority (ADI) (0.04 mg/kg body weight/day). However, we note that published toxicology studies of chlormequat suggest that re-evaluation of these safety thresholds may be necessary. For example, mice and pigs exposed to doses below the current RfD and ADI (0.024 and 0.0023 mg/kg body weight/day, respectively) showed decreased fertility . In another toxicology study, exposure during pregnancy to doses equivalent to a no-observed adverse effect level (NOAEL) of 5 mg/kg (used to calculate the US Environmental Protection Agency reference dose) resulted in changes in fetal growth and metabolism, as well as changes in body composition. Neonatal mice . In addition, regulatory thresholds do not take into account the adverse effects of mixtures of chemicals that may affect the reproductive system, which have been shown to have additive or synergistic effects at doses lower than exposure to individual chemicals , causing potential problems with reproductive health. health. Concerns about the consequences associated with current exposure levels, particularly for those with higher exposure levels in the general population in Europe and the US.
This pilot study of new chemical exposures in the United States shows that chlormequat is present in US foods, primarily in oat products, as well as in the majority of detected urine samples collected from nearly 100 people in the US, indicating ongoing exposure to chlormequat. Moreover, trends in these data suggest that exposure levels have increased and may continue to increase in the future. Given the toxicological concerns associated with chlormequat exposure in animal studies, and the widespread exposure of the general population to chlormequat in European countries (and now likely in the United States), coupled with epidemiological and animal studies, there is an urgent need Monitoring chlormequat in food and humans Chlormequat. It is important to understand the potential health hazards of this agricultural chemical at environmentally significant exposure levels, especially during pregnancy.
Post time: Jun-04-2024