The study, which tracked more than 500 Spanish girls between the ages of 7 and 10, links the presence of certain fungicides in urine to early menarche and that of the insecticide chlorpyrifos to delayed menarche, highlighting the impact of pesticides on pubertal development

Researchers from the University of Granada and the ibs.granada Biomedical Research Institute have analyzed the relationship between pesticide exposure and the age at first menstruation in 506 Spanish girls. The results, published in the journal Environmental Research, link higher concentrations of a fungicide residue to an earlier onset of the first period, while the presence of another compound derived from the insecticide chlorpyrifos is associated with a delayed onset. These findings, part of the INMA (Childhood and Environment) collaborative birth cohort study, underscore the importance of endocrine disruptors in children’s health and the need for further research into their effects.

Puberty is a process regulated by the endocrine system, and its timing can be altered by environmental factors. Several recent studies point to a trend toward earlier onset of puberty in girls, a phenomenon linked to a complex interplay between genetics, lifestyle, and exposure to chemicals capable of interfering with hormones. Among these substances are certain pesticides, widely used in agriculture and present in some everyday foods.

Endocrine disruptors are compounds that can mimic or block the action of hormones. Exposure to these endocrine disruptors, especially during critical stages of reproductive system development, has been identified as a possible factor contributing to both the advancement and delay of puberty. In the general population, foods produced through conventional agriculture are one of the main routes by which these pesticides enter the body, where they can have adverse effects.

The study, coordinated by the University of Granada and conducted as part of the INMA Project (Childhood and the Environment), followed 506 girls from four Spanish regions: Asturias, Guipúzcoa, Sabadell, and Valencia. To measure their exposure to pesticides, the research team analyzed urine samples collected when the girls were between 7 and 10 years old, during the period from 2013 to 2016. The girls were subsequently followed up until they were 14–16 years old to record the exact date of their first menstrual period.

The analyses revealed two significant associations. Regarding the early onset of menarche (first menstruation), higher concentrations of ethylenethiourea (ETU)—a residue from dithiocarbamate-type fungicides—were found to be associated with an earlier first period.

This compound is a known antithyroid agent, suggesting that its interference with thyroid hormones could accelerate the onset of puberty.

Conversely, the detection of TCPy, a metabolite of the insecticide chlorpyrifos, was associated with a delay in the onset of menarche. This effect was more pronounced in girls who were overweight or obese, suggesting a possible interaction between chemical exposure and nutritional status.

Changes in the age of menarche have significant long-term health consequences. An early onset of female puberty has been linked to psychological problems during adolescence and an increased risk of hormone-dependent cancers, such as breast cancer, in adulthood. These findings reinforce the importance of monitoring exposure to these compounds, better understanding their mechanisms of action, and implementing preventive measures.

Currently, both chlorpyrifos and several dithiocarbamate fungicides, such as mancozeb and maneb, are banned in the European Union (EU) due to their potential adverse effects on neurological development, fertility, and the environment. However, exposure to other pesticides, such as pyrethroids and glyphosate—whose safety remains a subject of debate—persists. As part of the “Farm to Fork” strategy of the Green Deal, the EU has set a target to reduce the use of chemical pesticides by 50% by 2030. In this context, the study’s authors note that the results, while pioneering in the prospective assessment of the effects of this type of pesticide, should be interpreted with caution, and they highlight the need for further research in other populations to confirm these findings.