26
Feb
Women in Agriculture at Elevated Risk of More Aggressive Breast Cancer from Pesticides, Study Finds
(Beyond Pesticides, February 26, 2026) Published in PLOS ONE, research in Brazil “analyzed the impact of occupational/household chronic exposure to pesticides on the clinicopathological profile of breast cancer in rural women from Paraná southwest, a predominantly rural landscape with large pesticide uses,†finding that “pesticide exposure favors the occurrence of more aggressive breast cancer.†The study highlights the disproportionate risks of pesticides to farmworkers, focusing on women, as it compares exposed and unexposed populations and breast cancer tumor/disease characteristics.
One of the study authors, Carolina Panis, PhD, discussed her earlier research at the Beyond Pesticides’ 42nd National Forum Series, The Pesticide Threat to Environmental Health: Advancing Holistic Solutions Aligned with Nature. In her previous work, Pesticide exposure and increased breast cancer risk in women population studies, Dr. Panis documents a number of pesticides that “can increase the risk of BC [breast cancer] development through various mutagenic [genetic mutations] and nonmutagenic mechanisms and can act directly as carcinogens or indirectly as biochemical modifiers and hormonal deregulators. The underlying mechanisms include endocrine disruption; genotoxicity; epigenetic changes [changes to gene function without changing DNA]; enhanced cell migration, invasion, and…†more. Dr. Panis and other researchers at the Forum support community-level understanding of the science and its relationship to debilitating and deadly disease patterns associated with toxic chemical exposure, so that people close to home and around the globe can effectively advocate for the necessary changes that are within reach. (See the recording here.)
Scientific literature documents how areas with an abundance of chemical-intensive agriculture, such as Brazil, experience increased adverse health and environmental effects. As the current study states: “Despite evidence on the negative impact of pesticides on human health, the country stands out among the top three pesticide consumers globally. The implications of this scenario on rural workers health, particularly women, is completely neglected, resulting in chronic illness such as breast cancer.â€
The authors continue, “To our knowledge, this is the first study that uses the described methodology [below] to predict the relationship of variables related to breast cancer severity in a population categorized according to their pesticide exposure profile.†As a result, the research highlights the link between occupational pesticide exposure and the occurrence of breast tumors with more aggressive clinicopathological (combining clinic and laboratory) findings. This includes “an increased frequency of disease recurrence, chemoresistance, death, and predominance of the molecular subtype Luminal B,†an aggressive, hormone receptor-positive (HR+) type of breast cancer.
Study Importance and Background
As the researchers point out, pesticide use in agriculture started with, and continues to be used, with the stated justification of increased food production for the growing world population, despite scientific literature that continues to showcase the acute and chronic consequences of their application and the availability of sustainable, productive, and profitable alternatives. Many pesticides are known endocrine disruptors, able to “influence the development of tumors in the female reproductive system, increase aromatase activity and estrogen production, reduce fertility, augment estrogen production, increase androgen availability, competitively bind to estrogen cell receptors, enhance proliferation of estrogen-sensitive cells, and inhibit corticosterone synthesis in the adrenal cortex.â€
Elevated risk of pesticide-induced breast cancer is associated with “various mutagenic and nonmutagenic mechanisms, acting either directly as carcinogens or indirectly as biochemical modifiers and hormonal disruptors,†the authors state. “The underlying mechanisms include endocrine disruption, genotoxicity, epigenetic [environmentally-driven heritable changes] alterations, enhanced cell migration, invasion, and stemness, angiogenesis [forming new capillary blood vessels], and tumor growth, among others.â€
Beyond Pesticides has extensively covered breast cancer and other common diseases, as documented in the Pesticide-Induced Diseases Database and through the Daily News Blog. In an article from last year, titled Pesticides Harming Immune Cell Function Linked to Elevated Breast Cancer Rate in Young Women, a study in Immunopharmacology and Immunotoxicology documents elevated rates of breast cancer in women with occupational pesticide exposure. This study was also of Brazilian women who were either occupationally or domestically exposed to pesticides and includes Dr. Panis as an author. (See additional Daily News on breast cancer here.)
In analyzing the Southeastern region of northern Paraná, Brazil in the study, the researchers reference three herbicides as the most prevalent, writing: “[The study] population is subject to considerable pesticide exposure, especially glyphosate, atrazine, and 2,4-dichlorophenoxyacetic (2,4-D), which are widely used in soybean, corn, and wheat monocultures in the region… Additionally, women occupationally exposed to areas where glyphosate, atrazine, and 2,4-D are predominantly used have a higher risk of developing breast cancer.†(See study here.)
The weed killer glyphosate has long been tied to adverse effects, including endocrine disruption, one of the mechanisms that can cause breast cancer. Research shows that in breast cancer cells, glyphosate exposure “leads to altered expression of cell proliferation-related genes, and dysregulation of key genes involved in tumor aggressiveness and metastasis [spread of cancer cells].†(See Daily News coverage on glyphosate here.)
Atrazine, a triazine herbicide, also exhibits endocrine-disrupting effects, with studies showing impacts to mammary glands and hormone levels. (See here and here.) “In breast cancer cells, atrazine alters protein expression and modulates antioxidant defense gene expression, promoting genomic instability and oxidative stress-induced damage, a recognized mechanism for breast cancer development and progression, also linked to immune deregulation in patients and inflammatory changes in normal mammary tissue in exposed women,†the authors note. (See Daily News coverage on atrazine here.)
Finally, the herbicide 2,4-D is associated with an increased risk of cancer, particularly mesothelioma and non-Hodgkin lymphoma, and endocrine disruption, along with many other adverse health effects including neurotoxicity, reproductive dysfunction, and developmental delays. (See Daily News coverage on 2,4-D here.)
This study highlights the growing trend of women in agriculture and the disproportionate risks they face. “[I]t has been estimated that women represent 43% of the world’s agricultural workforce,†the researchers state. They continue: “This trend has been observed in several regions of the world, such as in the European Union, where women represent 29% of rural workers, Brazil, where they represent 45%, and certain regions of Africa and Asia, where women’s representation can reach up to 60%. The feminization of agriculture may lead to an increase in the incidence of cancer in women.â€
Methodology and Results
As a cross-sectional and quantitative exploratory study, this research uses clinicopathological data from medical records, along with interviews, to categorize women as exposed or unexposed to pesticides and analyze that relationship with breast cancer diagnoses and characteristics. The data comes from the Francisco Beltrão Cancer Hospital, where a total of 923 women, from May 2015 to April 2023, had images suggestive of breast lesions. From that total, 349 patients were selected for study analyses after a diagnosis of breast cancer was determined by a pathologist.
“To characterize exposure, we previously performed a 2-year study aiming to get detailed information about patients’ exposure profile,†the authors write. “To reach this goal, patients were invited to complete a comprehensive questionnaire with 61 questions covering their current and past occupational history.†This led to the categorization of the study population as either occupationally exposed (n = 208) or unexposed (n = 141) to pesticides.
The women in the exposed group “reported spending at least 50% of their lives working with pesticides and having direct contact with these substances at least once a week,†with activities such as washing items contaminated with pesticides, preparing and diluting concentrated pesticides, and spraying diluted pesticides on crops. “Furthermore, 94% of the women in the exposed group reported performing these tasks without using PPE [personal protective equipment], not even gloves,†the researchers say. “As pesticides are primarily absorbed through the skin, this chronic and prolonged exposure represents a significant contamination route, surpassing potential exposure from food or water sources.â€
Noteworthy results of the study include:
- Exposed patients have a higher prevalence (32.83%) of the more aggressive Luminal B subtype of breast cancer.
- Pesticide exposure also leads to higher disease recurrence and chemoresistance as compared to unexposed individuals.
- “Breast cancer patients exposed to pesticides were also more likely to have distant metastases (1.4 times) and lymph node invasion (1.3 times) compared to patients not exposed.â€
- Of the patients with occupational exposure, “8.25% were stratified as low risk for death and recurrence, 55.87% into intermediate risk, and 35.87% were classified as high risk… About 7% of the patients died, 9.36% of the patients had disease recurrence, and 18.97% of the patients developed chemoresistance.†The low mortality rate can be attributed to all patients in the study being in Stage II, which is considered an early stage and often curable.
In summary, the authors write: “Our data suggest that pesticide exposure may be linked to more aggressive forms of breast cancer, with worse prognoses including increased recurrence, chemoresistance, and metastasis… Given these findings, we reiterate the urgency of discussing and changing policies that regulate the use of pesticides and the need to screen exposed populations and those at risk of developing more aggressive diseases.â€
Previous Research
As shown by the multitude of studies cited in the current study, there is a wide body of science connecting pesticide exposure to documented adverse health implications. Examples include:
- Immune dysregulation and inflammatory responses occur with pesticide exposure. (See here.)
- One study identifies “a predominance of intermediate risk for death and recurrence in women exposed to pesticides, characterized by the prevalence of Luminal B tumors in association intermediate size tumors (between 2 and 5 cm) and intermediate tumor grade.â€
- Additional research (see here and here) reports immune deregulation that favors the development of more aggressive tumors and triggers “the higher frequency of distant metastases and recurrence observed in patients occupationally exposed to pesticides.â€
- Another study of tumor samples from 158 patients finds that pesticide exposure is associated with pathogenic mutations, which suggests that pesticide exposure may impact cancer development, mutational burden, and disease progression.
Moving Forward
As the study authors mention, there is an urgency for pesticide regulation that better protects human health, as well as the need to support exposed populations with disproportionate risks for adverse health implications such as breast cancer. For decades, Beyond Pesticides has documented the regulatory deficiencies of the Environmental Protection Agency (EPA) in the U.S. and other regulatory bodies around the world. With the documented complexity of the pesticide threat to health and the environment that cannot be contained by regulatory mitigation measures, the transition to organic systems is critical as a holistic solution for ending pesticide dependency and contamination.
The widespread adoption of organic agriculture and land management practices eliminates the disproportionate risks to farmers, farmworkers, and their families from occupational exposure, as well as protects from pesticide drift and contamination in food, water, soil, and air. Learn more about how to take action and keep organic strong here and here, and support Beyond Pesticides’ mission of eliminating petrochemical pesticides and synthetic fertilizers by 2032.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Cazagranda, I. et al. (2026) Hidden risks associated with occupational pesticide exposure in women with breast cancer: High frequency of the Luminal B molecular subtype and occurrence of poor prognostic features, PLOS ONE. Available at: https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0339471.
