02
Apr
Study Finds Reproductive System Effects in Adolescents with Prenatal Pesticide Exposure
(Beyond Pesticides, April 2, 2025) In examining prenatal residential proximity of documented pesticide spraying in California to the menstrual cycle characteristics of 273 Latina adolescents, researchers report in the American Journal of Epidemiology a positive association between exposure to the insecticide methomyl and heavy bleeding. Other pesticides appear to influence menstrual symptoms as well. “Adolescents’ menstrual cycle characteristics can be ‘vital signs’ of health and impact quality of life,†the authors share. They continue, “To our knowledge, this is the first study to examine the association between prenatal pesticide exposure and menstrual outcomes in adolescents of any demographic group.â€
Menstrual cycle characteristics, such as dysmenorrhea (painful or uncomfortable menstrual cramps), irregularity, and heavy menstrual bleeding, can also be indicators of underlying health conditions, including endometriosis, polycystic ovary syndrome (PCOS), thyroid dysfunction, and bleeding disorders. By associating the pesticide exposure of mothers during pregnancy to impacts on their children, the researchers highlight important health risks for women and young girls that are often disregarded.
“The prenatal period is a critical period of reproductive development that may be particularly sensitive to endocrine disruption,†the researchers share. As previously reported by Beyond Pesticides, endocrine-disrupting chemicals are any synthetic or natural compounds that hinder endocrine system functions and create harmful effects on organisms, which includes many pesticides. The Endocrine Society emphasizes, “There are nearly 85,000 man-made chemicals in the world, many of which people come into contact with every day. Only about one percent of them have been studied for safety; however, 1,000 or more of these chemicals may be EDCs [endocrine-disrupting chemicals] based on their probable endocrine-interfering properties.â€
The authors of the article in American Journal of Epidemiology, affiliated with the University of California Berkeley and San Francisco (particularly through the Center for Environmental Research and Community Health), focus their research on California residents within the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. California represents an area of intensive cultivation, utilizing many agricultural pesticides, since the state “grows over a third of the United States’ vegetables and over three-quarters of the country’s fruits and nuts,†according to the researchers.
The study participants, with an average age of 16.3 years, were evaluated through a questionnaire regarding menstrual characteristics, including cycle length irregularities, painful menstruation, and heavy bleeding. These characteristics, in referencing their maternal residential addresses, were compared to California’s Pesticide Use Reporting database to determine the association between prenatal residential proximity to 11 agricultural pesticides and any menstrual cycle symptoms. The chemicals were evaluated singularly and adjusted for co-exposure since “[a]gricultural pesticide use practices often result in simultaneous and sequential exposure to multiple highly correlated active ingredients from different classes,†the authors state.
The pesticides included in the study are from six different pesticide classes. “These active ingredients were permethrin [pyrethroid insecticide], methomyl [carbamate insecticide], imidacloprid [neonicotinoid insecticide], maneb/mancozeb [ethylenebisdithiocarbamate (EBDC) fungicides], and glyphosate [herbicide]. For the organophosphate insecticides, multiple active ingredients met our inclusion criteria: acephate, chlorpyrifos, diazinon, malathion, oxydemeton-methyl, and dimethoate,†the researchers note.
As a result, the authors report, “We found evidence that prenatal exposure to endocrine-disrupting pesticides may impact certain adolescent menstrual cycle characteristics.†The most notable association in the single exposure model is that a 2-fold increase in prenatal methomyl exposure correlates to a 29% increase in heavy menstrual flow. The researchers share that this relationship also “approached statistical significance in our joint exposure model.â€
They continue, “Other instances where results approached statistical significance in joint exposure models were: permethrin exposure and increased odds of painful cycles [and] oxydemeton-methyl [organothiophosphate insecticide] exposure and increased odds of pain medication use during cycles.†These findings suggest prenatal pesticide exposure is associated with subsequent menstrual cycle symptoms in children.
As the authors point out, these symptoms can have a strong negative impact on individuals’ quality of life and mental health. One study from Australia reports that teens with menstrual problems have significantly lower quality of life scores than healthy teens. Additional studies find that dysmenorrhea (painful or uncomfortable menstrual cramps) is “positively associated with academic absenteeism, depression, body image issues, and social isolation.†(See studies here, here, here, here, and here.) Symptoms that include heavy and prolonged menstrual bleeding can also be markers of bleeding disorders, interfere with mental and physical health, and lead to anemia and period-related stress. (See here and here.)
“Many currently used pesticides contain active ingredients that are known or suspected endocrine-disrupting chemicals (EDCs), which may interact with the endocrine system, preventing proper function by mimicking or blocking hormonal interactions,†the researchers note. Within the study, evidence of endocrine disruption in scientific literature is shared, including:
- “Carbamate insecticides, organophosphate insecticides, pyrethroids insecticides, glyphosate herbicides, and manganese fungicides can disrupt normal hormonal signaling along the estradiol, progesterone, and thyroid pathways and dysregulate the hypothalamic-pituitary-gonadal (HPG) axis, all of which are important to the function of the female reproductive system.†(See studies here, here, here, and here.)
- Oxidative stress, as a result of organophosphates and neonicotinoid insecticides, can alter the epigenome, resulting in hormonal imbalances. (See here and here.)
- “In rodent models, exposure to commonly used pesticides such as imidacloprid and chlorpyrifos have been shown to alter estrous cyclicity and adversely affect the structure and function of the uterus and ovaries.â€
- “In vivo and in vitro studies on prenatal EDC exposures consistently find associations with deleterious effects on female reproductive health.†(See studies here, here, and here.)
- Studies in rodents, with pesticide exposure from pregnancy to lactation, find “differences in time to puberty, age at first estrous, sex hormone concentrations, uterine and ovarian function, and fertility in female offspring.†(See here, here, here, and here.)
- “[A] study in a mouse model found that exposure to methomyl and another carbamate, carbofuran, disrupted estrous cycle length.â€
- “Maternal exposure to pyrethroid insecticides has been associated with delayed sexual maturation, abnormal estrous cycle, and altered ovarian and uterine function in female rats and with delayed puberty onset and diminished ovarian reserve in humans.†(See studies here, here, here, and here.)
- Studies of the metabolites of chlorpyrifos and diazinon, confirmed in urinary concentrations, are associated with “increased odds of endometriosis, a disease characterized by menstrual pain, heavy menstrual bleeding, and other cycle irregularities.â€
- “Organophosphate pesticide exposure disrupted estrous cycle cyclicity in rats and mice and shorter duration of menstrual bleeding and higher odds of irregular menstrual cycles among Chinese women.†(See here, here, here, and here.)
As was shared in a Beyond Pesticides’ article titled “Multiple Studies Link Adverse Effects on Female Reproductive Health with Endocrine Disrupting Chemical Exposure,†research in Frontiers in Public Health showcases the wide body of science connecting adverse effects to the female reproductive system, such as infertility, with exposure to endocrine-disrupting chemicals. As the researchers conclude from these results: “The impact of EDCs extends beyond lowering the rate of a successful pregnancy and increasing the risk of miscarriage in women; they also impair the future reproductive health of the fetus.†This highlights how infants and children are at a disproportionate risk with pesticide exposure, as this is a crucial developmental window.
Additional Beyond Pesticides’ coverage, following International Women’s Day this year, shares excerpts from The Report of the Special Rapporteur on the implications for human rights of the environmentally sound management and disposal of hazardous substances and wastes, by Marcos Orellana, that was delivered to the 79th Session of the United Nations General Assembly in July 2024. He states: “Some of the most serious impacts of exposure to pesticides concern female reproductive health damage. Exposures to hazardous pesticides during pregnancy can cause miscarriages, premature births, birth anomalies and low birthweight… [P]esticides generated a wide spectrum of reproductive health problems, such as male and female infertility, endocrine disruption, some types of cancer, germ cell mutations, damage to pregnancy and fetal development, effects on child development and puberty and transgenerational effects, among others.â€
Also shared in Daily News regarding International Women’s Day was a compilation of studies on women’s health to emphasize the disproportionate risks women face from toxic chemicals that are often unaccounted for and even dismissed throughout pesticide regulatory review processes. The inequalities in pesticide threats to women include health effects ranging from cancer, sleep disorders, gut dysbiosis, and diabetes to epigenetic effects, developmental delays, neurotoxicity, and reproduction dysfunction, including infertility and negative birth outcomes.
Beyond Pesticides has long since covered the regulatory deficiencies of the U.S. Environmental Protection Agency (EPA). In the Daily News post titled “Human Health Disregarded with Obsolete Regulations and Risk Management, Researchers Find,†it is stressed how assessments relying on outdated principles and expectations put human health at risk. Gender inequalities within these assessments are one of many data gaps that threaten human health. (See more on EPA failures here.)
To mitigate the endocrine-disrupting effects of pesticides that display detrimental long-term health effects both directly and indirectly, implementation of the holistic solution of organic land management is necessary. By eliminating the use of petrochemical pesticides and synthetic fertilizers, organic methods safeguard public health, for women, men, and children, as well as mitigate the crises of climate change and biodiversity.
To learn more about endocrine disruption, listen to keynote speaker Tracey Woodruff, PhD, from the second session of the 41st National Forum Series — Imperatives for a Sustainable Future and to learn more about the benefits of organic land management, see here and here.
Take action by helping to transition your community to organic practices through the Parks for a Sustainable Future program as a Parks Advocate and become a member of Beyond Pesticides to add your voice to the organic solution. Stay informed by signing up for our Action of the Week and Weekly News Updates, delivered straight to your inbox!
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Paul, J. et al. (2025) Prenatal residential proximity to endocrine disrupting agricultural pesticides and menstrual cycle characteristics among Latina adolescents in California, American Journal of Epidemiology. Available at: https://academic.oup.com/aje/advance-article/doi/10.1093/aje/kwaf059/8083004.