11
Jun
Literature Review Compiles Decades of Research Finding Linkage to Pesticide Exposure and Breast Cancer
(Beyond Pesticides, June 11, 2024) Published in Science of The Total Environment in May, a comprehensive literature review of population-based studies finds strong linkages between direct and acute pesticide exposure and elevated risk of breast cancer (BC). A majority of the studies analyzed in this review were based on population groups in the United States, but also extends to Australia and three European countries (Greece, France, and Italy). Included in these studies are women who worked in chemical-intensive agricultural settings, directly sprayed pesticides in their at-home gardens, and/or handled pesticide-contaminated clothing. The findings in this literature review underscore organic advocates’ concerns of relying on pesticide substitution models that inevitably impact the health of land stewards, farmers, farmworkers, and the broader public rather than transforming food systems to an organic model that bans the use of toxic petrochemical-based pesticides.
The goal of this review was to synthesize existing literature on pesticide exposure and breast cancer to determine the specific pathways and underlying mechanisms that contribute to female participants’ heightened risk. This literature review was published online by researchers at the University of Arizona’s R. Ken Coit College of Pharmacy and Coit Center for Longevity and Neurotherapeutics and the Laboratory of Tumor Biology at the State University of Western Paraná in Brazil. Author Carolina Panis, PhD, has written extensively on the nexus of breast cancer and various potential linkages, including pesticide exposure. Coauthor Bernardo Lemos, PhD specializes in evolutionary and population genomics, employing this background in studies identifying linkages to various types of cancers at the cellular level. Drs. Panis and Lemos point out that the majority of studies to-date on breast cancer and pesticides comprise women who live in heavy-use areas or experience indirect exposure from husbands who are occupationally exposed. Most of the studies compiled for this literature review, however, focus on “direct†exposure (women who apply pesticides themselves in agricultural or home gardening contexts, as well as those who handled contaminated clothes while simultaneously engaging in one of the former methods of directly spraying pesticides). “The significant associations are related to women’s direct exposure to pesticides, including being in the field during pesticide application, not wearing personal protection equipment during pesticide spraying and handling, washing pesticide-contaminated clothes, being engaged in farming, working on crops, or living under spray drifts.â€
In the initial search, 598 articles (published before January 26, 2023) were collected through Google Scholar, PubMed, and Scielo databases using the descriptors “breast cancer risk,†“occupational risk,†and “pesticide.†After screening, the researchers assessed 105 full-text articles. The initial screening process removed reviews, meta-analyses, animal studies, in vitro studies, mixed toxic substance exposure, studies on male breast cancer, among other criteria. The researchers ultimately focused on 11 studies. These studies were published between 2000 and 2022 in various journals focused on cancer, occupational and environmental health, and epidemiology. The sample size for these population-based studies ranged from 128 to 30,145 screened participants. The types of exposure for this final group of studies includes those living on farms or working in the agricultural sector, household exposure through direct spraying or washing clothes that had pesticide residues, among others.
Insecticides—specifically malathion, chlorpyrifos, terbufos, chlordane, and dieldrin—were the predominant group of pesticides of focus in the studies reviewed, however Drs. Panis and Lemos indicate the need to track the life-long exposure implications for female agricultural workers and pesticide applicators on other widely-used pesticides, including atrazine and glyphosate. “Ten of the eleven selected studies reported at least one significant association between some aspect of pesticide exposure and BC risk,†the researchers report in summarizing their results.
This literature review supports earlier research findings that indicate linkages between pesticide exposure and underlying mechanisms contributing to the development of breast cancer. A 2023 study published in Environmental International determines that a variety of chemicals (piperidine insecticide, 2,4-diitrophenol, benzo[a]carbazole, and a benzoate derivative) contributed to inflammation pathways that lead to the development of breast cancer. Also published in 2023, a study in Ecotoxicology and Environmental Safety finds that exposure to atrazine impacts 4T1 breast cancer cell development and significantly increases cancer cell spread and tumor size, as well as suppression of immune cell function. Other pesticides registered with the U.S. Environmental Protection Agency (EPA), including those registered for general use and others restricted for use by certified applicators, have been found to act as endocrine disruptors, contributing to the development of breast cancer—discovered in the cases of glyphosate-based herbicides in a 2022 study published in Chemosphere and seven neonicotinoid insecticides (thiamethoxam, imidacloprid, nitenpyram, thiacloprid, clothianidin, acetamiprid, and dinotefuran) in a 2022 study published in Environmental International. These two studies build on a comprehensive research report published in Environmental Health Perspectives in 2021, which finds 296 chemicals linked to breast cancer risk through the increased production of estradiol (estrogen-like compound) or progesterone production of H295R cells responsible for hormone synthesis. For more information, the Pesticide-Induced Disease Database entry on breast cancer offers a list of peer-reviewed research studies, literature reviews, and additional resources.
Breast Cancer Awareness Month is every October, and Beyond Pesticides has a dedicated section on its website that provides resources and opportunities to engage in the scientific literature highlighting the chemicals implicated with breast cancer-inducing characteristics, disproportionate risks, sex-specific risks, generational impacts, and implications along race and socioeconomic status. Advocates continue to urge a wholesale transformation of land management and agricultural practices away from the reliance on endocrine-disrupting chemicals that heighten the risk of breast cancer. They see investing in organic, be it as a consumer, gardener, or farmer, as a critical solution. See Eating With a Conscience to learn about what chemicals are being sprayed on commonly purchased products and produce to better inform your next grocery trip. And, see Keeping Organic Strong to learn about National Organic Program and opportunities to engage with the public review comment periods with the aim of strengthening federal organic standards.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Science of The Total Environment
