Environmental Pesticide Exposure and Reproductive Development: Recent Evidence on Menstruation and Breast Development in Girls

Featured image caption: Women play a central role in agriculture, where pesticide exposure is common. Even without direct occupational contact, proximity to croplands and related activities can increase exposure, with emerging evidence suggesting these chemicals may disrupt hormonal pathways and influence reproductive development in girls. [[File:Role of women in agriculture in Punjab (5712932498).jpg|Role_of_women_in_agriculture_in_Punjab_(5712932498)]]. Source: Public domain via Wikimedia commons

Source articles:

1.         Age at Menarche and Exposure to Non-Persistent Pesticides in Spanish Girls From the INMA (Environment and Childhood) Project. Freire C, Olivas-Martinez A, Castiello F, et al. Environmental Research. 2026;300:124450. doi:10.1016/j.envres.2026.124450.

2.         Childhood Exposure to Non-Persistent Pesticides and Pubertal Development in Spanish Girls and Boys: Evidence From the INMA (Environment and Childhood) Cohort. Castiello F, Suárez B, Beneito A, et al. Environmental Pollution (Barking, Essex : 1987). 2023;316(Pt 2):120571. doi:10.1016/j.envpol.2022.120571.

Introduction

The timing of pubertal development in girls has changed over recent decades, with many populations showing earlier breast development and menarche. While obesity is an important factor, growing evidence suggests that environmental endocrine-disrupting chemicals (EDCs), particularly pesticides, may also influence reproductive development. Recent research has examined how exposure to non-persistent pesticides—those commonly found in daily environments—may affect the timing of menstruation and breast development in girls.

Key Original Research: The INMA Project Findings

Age at Menarche and Non-Persistent Pesticides (2026)

The most recent longitudinal evidence comes from Freire et al. (2026), who studied 506 Spanish girls from the INMA (Environment and Childhood) Project. Researchers measured pesticide metabolites in urine collected at ages 7–10 and followed participants until age 16 to assess the timing of first menstruation.

The results showed contrasting patterns depending on the type of pesticide exposure. Higher levels of trichloro-2-pyridinol (TCPy), a marker of the organophosphate chlorpyrifos, were associated with slightly later menarche, particularly in girls with overweight or obesity.

In contrast, higher levels of ETU, a metabolite of dithiocarbamate fungicides, were associated with earlier menarche in a clear dose-related pattern. This association was strongest in girls with normal or low body weight, suggesting that body composition may influence susceptibility to these chemicals.

Exposure in this cohort is likely not linked to a single source but is multifactorial, including prenatal exposure, residential pesticide use, diet, and proximity to agricultural areas.

Breast Development and Pesticide Exposure (2023)

Complementary findings from the same cohort (Castiello et al., 2023) examined 606 girls aged 7–11 years. The study found that higher ETU levels were associated with a markedly increased likelihood of breast development, especially among girls with lower or normal body weight.

Additionally, exposure to a non-specific organophosphate metabolite (DETP) was associated with higher odds of overall pubertal development.

Together, these findings suggest that early-life exposure to certain pesticides may influence the timing of breast development and puberty, and that nutritional status may modify these effects.

Systematic reviews provide a broader perspective. A 2021 review found that different pesticide classes may have distinct effects on puberty timing, including delayed development in some cases and earlier onset in others.

However, a 2022 meta-analysis concluded that overall evidence remains inconsistent, largely due to differences in study design, exposure assessment, and definitions of pubertal outcomes. This highlights the complexity of studying environmental chemicals and human development.

Mechanisms of Action

Hypothalamic-Pituitary-Gonadal Axis Disruption. Pesticides may affect pubertal development by interfering with the endocrine system, particularly the hormonal signals that regulate growth and reproduction. Studies in agricultural workers have demonstrated that organophosphate pesticides exposure alters follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels.

In Mexican agricultural workers, urinary OP metabolites were negatively associated with LH and FSH levels. A study of Spanish male adolescents found that detectable TCPy was associated with decreased FSH and anti-Müllerian hormone (AMH), while IMPy (diazinon metabolite) was associated with increased FSH and AMH but decreased LH.

Other studies suggest that exposure to these chemicals may alter estrogen and thyroid hormone pathways, both of which play key roles in regulating the timing of puberty.

Dithiocarbamate Fungicides and Estrogenic Activity. Dithiocarbamate fungicides, through their metabolite ETU, may also disrupt hormonal balance. Experimental studies suggest that these compounds can interfere with estrogen and thyroid systems, both of which are essential for normal reproductive development.

Animal studies further indicate effects on ovarian function and egg cell development, supporting their potential role in earlier puberty onset observed in population studies.

Clinical and Public Health Implications

The evidence from recent longitudinal studies demonstrates that contemporary pesticide exposures at environmentally relevant levels are associated with measurable alterations in pubertal timing. The bidirectional effects observed—with organophosphates delaying and dithiocarbamate fungicides advancing pubertal development—underscore the complexity of EDC effects and the importance of considering specific chemical classes rather than treating all pesticides as a homogeneous group.

The effect modification by body mass index is particularly noteworthy from a public health perspective. Girls with normal or low body weight appear more susceptible to ETU-induced advancement of puberty, while girls with overweight or obesity show stronger associations between organophosphate exposure and delayed menarche. These findings suggest that nutritional status and chemical exposures may interact to influence pubertal timing through distinct pathways.

Earlier age at menarche has been associated with increased lifetime risk of breast cancer, cardiovascular disease, and metabolic disorders. Conversely, delayed puberty can have psychosocial consequences and may indicate broader endocrine dysfunction. Understanding the environmental determinants of pubertal timing is therefore critical for both individual health and population-level disease prevention.

Exposure Patterns and Biomonitoring

Systematic reviews of ethylenethiourea (ETU) biomonitoring studies indicate widespread population exposure to dithiocarbamate fungicides. Median urinary ETU levels in environmentally exposed populations range from 0.15 to 4.7 μg/g creatinine in adults and 0.24 to 0.83 μg/g creatinine in children, while agricultural populations show substantially higher exposures (0.42 to 49.6 μg/g creatinine). ETU can form in foods treated with dithiocarbamate fungicides, particularly during heat processing, with 3-30% conversion during boiling of various produce items.

Occupational studies of workers applying dithiocarbamate fungicides without protective equipment have documented increases in thyroid-stimulating hormone and cytogenetic damage, demonstrating the biological activity of these compounds at high exposure levels and supporting plausibility for effects at lower environmental exposures.

Research Gaps and Future Directions

Despite recent advances, important gaps remain in understanding how pesticides influence pubertal development.

Most studies measure exposure at a single point in time, which may not capture critical windows of vulnerability during childhood development. In addition, real-life exposure involves mixtures of multiple pesticides, but most research still focuses on individual compounds.

There is also limited evidence from regions with high pesticide use, where exposure levels may be greater than those reported in Europe or North America.

Future studies should focus on long-term exposure tracking, hormonal changes over time, and factors that may influence individual susceptibility, such as genetics and nutritional status.

Conclusions

In conclusion, emerging longitudinal evidence suggests that everyday exposure to certain non-persistent pesticides may contribute to measurable shifts in pubertal timing in girls, potentially through disruption of endocrine, inflammatory, and metabolic pathways. These findings are especially relevant for communities with greater environmental and occupational exposure burdens, including agricultural populations, rural communities located near pesticide-treated fields, low-income households with limited access to environmental protections, and children living in regions where pesticide regulation and biomonitoring remain limited. Because nutritional status appears to modify susceptibility, populations already affected by food insecurity, obesity, or other metabolic vulnerabilities may experience disproportionate health effects.

These observations also raise important follow-up questions that remain unanswered, including which developmental windows are most sensitive to pesticide exposure and how chronic low-dose mixtures of pesticides interact with obesity, diet, stress, or genetic susceptibility to influence endocrine development.

Together, these findings underscore the need for more comprehensive environmental health surveillance, stronger exposure prevention strategies, and interdisciplinary research aimed at identifying which children are most vulnerable, why susceptibility differs between individuals, and how modifiable environmental factors may shape reproductive and long-term health trajectories across the lifespan.

Additional references

1. Exposure to Non-Persistent Pesticides and Puberty Timing: A Systematic Review of the Epidemiological Evidence. Castiello F, Freire C. European Journal of Endocrinology. 2021;184(6):733-749. doi:10.1530/EJE-20-1038.
2. Prenatal and Postnatal Exposures to Endocrine Disrupting Chemicals and Timing of Pubertal Onset in Girls and Boys: A Systematic Review and Meta-Analysis. Uldbjerg CS, Koch T, Lim YH, et al. Human Reproduction Update. 2022;28(5):687-716. doi:10.1093/humupd/dmac013.
3. Female Reproductive Toxicity After Exposure to Malathion or Diazinon: A Systematic Review of Rodent and Human Studies. Barbosa IG, Lazzari VM, Araújo Leite GA. Critical Reviews in Toxicology. 2025;:1-12. doi:10.1080/10408444.2025.2548581.
4. Pesticide Exposure Alters Follicle-Stimulating Hormone Levels in Mexican Agricultural Workers. Recio R, Ocampo-Gómez G, Morán-Martínez J, et al. Environmental Health Perspectives. 2005;113(9):1160-3. doi:10.1289/ehp.7374.
5. Organophosphate Pesticide Exposure, Hormone Levels, and Interaction With PON1 Polymorphisms in Male Adolescents. Suárez B, Vela-Soria F, Castiello F, et al. The Science of the Total Environment. 2021;769:144563. doi:10.1016/j.scitotenv.2020.144563.
6. Alterations in Reproductive Hormone Levels Among Farm Women and Their Children Occupationally Exposed to Organophosphate Pesticides. Medithi S, Kasa YD, Jee B, Venkaiah K, Jonnalagadda PR. Women & Health. 2022 May-Jun;62(5):454-464. doi:10.1080/03630242.2022.2085844.
7. Currently Used Pesticides and Their Mixtures Affect the Function of Sex Hormone Receptors and Aromatase Enzyme Activity. Kjeldsen LS, Ghisari M, Bonefeld-Jørgensen EC. Toxicology and Applied Pharmacology. 2013;272(2):453-64. doi:10.1016/j.taap.2013.06.028.
8. Reproductive Toxicity and Thyroid Effects in Sprague Dawley Rats Exposed to Low Doses of Ethylenethiourea. Maranghi F, De Angelis S, Tassinari R, et al. Food and Chemical Toxicology : An International Journal Published for the British Industrial Biological Research Association. 2013;59:261-71. doi:10.1016/j.fct.2013.05.048.
9. The Effects of the Endocrine Disruptors Dithiocarbamates on the Mammalian Ovary With Particular Regard to Mancozeb. Cecconi S, Paro R, Rossi G, Macchiarelli G. Current Pharmaceutical Design. 2007;13(29):2989-3004. doi:10.2174/138161207782110516.
10. Systematic Review of Human Biomonitoring Studies of Ethylenethiourea, a Urinary Biomarker for Exposure to Dithiocarbamate Fungicides. Stadler K, Li X, Liu B, et al. Environmental Pollution (Barking, Essex : 1987). 2022;292(Pt B):118419. doi:10.1016/j.envpol.2021.118419.
11. Ethylenethiourea (ETU) in Relation to Use of Ethylenebisdithiocarbamate (EBDC) Fungicides. Lentza-Rizos C. Reviews of Environmental Contamination and Toxicology. 1990;115:1-37. doi:10.1007/978-1-4612-3416-6_1.
12. Thyroid Hormones and Cytogenetic Outcomes in Backpack Sprayers Using Ethylenebis(dithiocarbamate) (EBDC) Fungicides in Mexico. Steenland K, Cedillo L, Tucker J, et al. Environmental Health Perspectives. 1997;105(10):1126-30. doi:10.1289/ehp.971051126.

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