This Spanish cohort study of 506 girls measured pesticide biomarkers in urine at ages 7–10 and followed participants until 14–16 to record menarche. Higher ethylenethiourea (ETU) levels were linked to earlier first periods, while detection of TCPy (a chlorpyrifos metabolite) was associated with later menarche, especially in overweight or obese girls. The results raise concerns about endocrine-disrupting pesticides, but authors urge caution and call for replication and more detailed exposure assessment.
Spanish Cohort Study Links Two Pesticide Biomarkers to Earlier or Later First Periods in Girls
Photo Credit: University of Granada
A new Spanish cohort study reports associations between two pesticide-related urinary biomarkers and the timing of menarche (first menstrual period) in girls. The findings suggest that routine exposure to certain pesticide residues may be linked to either earlier or later onset of puberty, depending on the compound.
Study Design
Researchers from the University of Granada and the ibs.granada Biomedical Research Institute analyzed data from 506 girls who provided urine samples between 2013 and 2016 at ages 7–10. The participants, drawn from Asturias, Guipúzcoa, Sabadell and Valencia, were followed until ages 14–16 to record when menarche occurred. Urinary biomarkers were used as exposure indicators.
Key Findings
The clearest associations involved ethylenethiourea (ETU) and TCPy. Higher urinary ETU — a metabolite indicating exposure to dithiocarbamate fungicides — was associated with earlier menarche. By contrast, detection of TCPy, a breakdown product of chlorpyrifos, was associated with later menarche, particularly among girls who were overweight or obese.
Implications
Timing of puberty has long-term health implications. Earlier menarche is linked with increased risk of psychological difficulties in adolescence and higher lifetime risks for hormone-related conditions, including breast cancer. The opposing directions of association seen for ETU and TCPy underscore concerns about endocrine-disrupting chemicals, which can mimic or interfere with hormonal signaling at vulnerable developmental windows.
Regulatory Context and Environmental Concerns
Some pesticides implicated in health and environmental harms have already been restricted. The European Union has banned chlorpyrifos and several dithiocarbamate fungicides (including mancozeb and maneb) because of risks to neurological development, fertility, and ecosystems. Nevertheless, exposures to other pesticides — such as pyrethroids and glyphosate — persist, and policy efforts like the EU Farm to Fork strategy aim to reduce chemical pesticide use.
Limitations and Next Steps
The authors describe this work as pioneering but caution that observational associations do not prove causation. Single urine measurements provide exposure estimates but may not capture long-term patterns. The study calls for replication in other populations, more detailed exposure assessment, and research to clarify biological mechanisms and susceptible subgroups.
Bottom line: This study adds evidence that early-life pesticide exposures may influence when puberty begins, but further research is needed before drawing firm conclusions or changing individual behaviors.
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