- A study in PLOS ONE found that chronic occupational and household pesticide exposure is linked to more aggressive breast cancer among rural women in southern Brazil, including higher rates of recurrence, chemoresistance and metastasis.
- The research analyzed 349 women diagnosed with breast cancer between 2015 and 2023, with 208 classified as occupationally exposed. Most reported handling pesticides weekly without personal protective equipment, making skin absorption a major contamination route.
- Exposed women were 32.83% more likely to have Luminal B breast cancer, an aggressive hormone receptor-positive subtype, and faced higher risks of distant metastases, lymph node invasion, recurrence and chemotherapy resistance.
- The study highlighted three commonly used herbicides in the region, glyphosate, atrazine and 2,4-D, which are associated with endocrine disruption, immune system changes and mechanisms that promote tumor growth and metastasis.
- Researchers, including Carolina Panis, stressed the need for stricter pesticide regulations and expanded protections for agricultural workers, especially women, noting that Brazil remains one of the top three global pesticide consumers and that increasing female participation in agriculture may amplify cancer risks.
A new study published in PLOS ONE has found that chronic occupational and household exposure to pesticides is associated with more aggressive forms of breast cancer among rural women in southern Brazil.
The research focused on women in Paraná’s southwest region, a predominantly rural area marked by large-scale pesticide use. Comparing women with documented occupational exposure to those without, researchers concluded that pesticide exposure “favors the occurrence of more aggressive breast cancer,” including higher rates of recurrence, chemoresistance and metastasis.
The cross-sectional study analyzed medical records and interviews from 349 women diagnosed with breast cancer between 2015 and 2023 at the Francisco Beltrão Cancer Hospital. Of those, 208 were categorized as occupationally exposed to pesticides after completing detailed questionnaires about their work histories.
Women in the exposed group reported spending at least half their lives working with pesticides, with direct contact at least once a week. Tasks included mixing and diluting chemicals, spraying crops and washing contaminated clothing or equipment.
Notably, 94% said they performed these activities without personal protective equipment, including gloves. Because pesticides are primarily absorbed through the skin, researchers said this long-term contact represents a significant route of contamination.
The study found that 32.83% of exposed patients were diagnosed with Luminal B breast cancer, an aggressive hormone receptor-positive subtype. Exposed women were also 1.4 times more likely to develop distant metastases and 1.3 times more likely to experience lymph node invasion compared to unexposed patients. Higher rates of disease recurrence and resistance to chemotherapy were also observed.
Although all patients were diagnosed at Stage II, an early and often treatable stage, more than one-third of exposed patients were classified as high risk for death or recurrence. About 7% of exposed patients died during the study period, nearly 19% developed chemoresistance, and more than 9% experienced recurrence.
Researchers pointed to several biological mechanisms that may explain the link. Many widely used pesticides are known endocrine disruptors, capable of interfering with hormone regulation, increasing estrogen production, altering gene expression and promoting tumor growth. The authors cited mechanisms including genotoxicity, epigenetic alterations, enhanced cell migration and angiogenesis.
The study identified three herbicides commonly used in soybean, corn and wheat monocultures in the region – glyphosate, atrazine and 2,4-dichlorophenoxyacetic acid (2,4-D) – as prevalent exposures among the population studied. Previous research has linked these chemicals to endocrine disruption, immune system changes and cellular processes associated with cancer development and progression.
Brazil is one of the world’s largest consumers of agricultural pesticides
The authors noted that despite growing scientific evidence of health risks, the country remains one of the top three global pesticide users. BrightU.AI‘s Enoch noted that agricultural pesticides in Brazil have seen a significant and concerning increase in usage since the change in government in 2019, with over 1,200 products, including those banned in their countries of origin, being approved.
Researchers also highlighted the increasing presence of women in agriculture, estimated at 43% of the global agricultural workforce and about 45% in Brazil, warning that the “feminization” of agriculture could heighten cancer risks among women in rural communities.
These findings add to a growing body of research examining the long-term health consequences of chronic pesticide exposure.
One of the study authors, Carolina Panis, PhD, discussed a similar stance in her previous research at the Beyond Pesticides 42nd National Forum Series, titled “The Pesticide Threat to Environmental Health: Advancing Holistic Solutions Aligned with Nature.”
Panis’ research notes that some pesticides may act directly as carcinogens, while others function indirectly as biochemical modifiers or hormonal disruptors. The biological pathways involved include endocrine disruption, genotoxicity, epigenetic changes that alter gene function without modifying DNA sequences, enhanced cell migration and invasion, and other processes linked to tumor growth and metastasis.
Their findings suggest that occupational pesticide exposure is associated with more severe clinicopathological outcomes, including increased recurrence, chemoresistance, higher mortality rates and a predominance of the Luminal B molecular subtype.
Panis said the results underscore the urgency of reexamining pesticide regulations and expanding protective measures for agricultural workers.
Watch this video about the book “Killing Cancer—Not People” by Dr. Robert G. Wright.
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Sources include:
BeyondPesticides.org 1
BeyondPesticides.org 2
Journals.PLOS.org
BrightU.ai
Brighteon.com
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