15
Jan
Literature Review Shows the Depth of Research Linking Pesticide-Induced Effects on Immune System, Leading to Disease Outcomes
(Beyond Pesticides, January 15, 2025) There is robust scientific literature that unpacks the adverse human health effects of pesticide exposure, however immunological impacts do not receive adequate attention in regulatory review processes, according to an in-depth literature review. In a piece published in Frontiers in Immunology (2024) critiquing recent peer-reviewed scientific studies, as well as unpublished research produced by the Institute of Biology and Experimental Medicine in partnership with the National Scientific and Technical Research Council in Argentina, researchers assess immune system effects of pesticide exposure, which creates the conditions for deadly health conditions including various forms of cancer.
The focus of this study, according to the authors, is “to critically review fundamental aspects of toxicological studies conducted on PPPs [Plant Protection Products] to provide a clearer understanding of the risks associated with exposure to these compounds on human health.†PPPs are pesticide products that contain more than one active ingredient, and can include synergistic ingredients that supercharge them alongside inert ingredients that pesticide companies are not legally required to disclose under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), but are often manipulated biologically and chemically active.
Most studies analyze the toxicological impacts of active ingredients in isolation rather than testing the entire product, including glyphosate-based herbicides. Additionally, authors identify an insufficient body of research measuring cancer biomarkers connected to specific pesticides, even though they “are essential to precisely and timely understand the extent and depth of the problem.†The researchers acknowledge that while more research is also necessary to better understand the impacts of chemical mixtures on agricultural communities and the broader public, further investigations into mechanisms of toxicity for individual pesticides are integral to public health and awareness in regulatory decision-making.
Immune Response and Pesticides
The literature review finds that more studies are needed to determine immunotoxic impacts of pesticides in human subjects, with the researchers pointing to three relevant peer-reviewed studies. These studies are similar in that they assess cytokine levels among farmworker and farmer populations to determine relationships between pesticide exposure and deadly diseases, specifically cancer. The National Cancer Institute defines cytokines as “a type of protein that is made by certain immune and non-immune cells and has an effect on the immune system.†Simply put, cytokines act as signals to the immune system. There is evidence of pro-inflammatory cytokines, including but not limited to Th-2 cytokines, that can create the conditions for various types of cancers, infections, and other severe diseases.
The first study (published in Science of the Total Environment in 2024) assesses pesticide exposure among 280 individuals in southeastern Spain. 189 of the participants made up the exposed group working in an indoor setting (horticultural greenhouse). The control group consisted of nonagricultural workers living near the greenhouses. The majority of participants from both subgroups were tested for 27 immunoregulatory proteins during high and low pesticide exposure periods. Ultimately, the researchers determined asthmatic conditions can be attributed to increased inflammatory cytokine levels among greenhouse workers in this study, among other health issues.
The second study (published in Ecotoxicology and Environmental Safety in 2020) assesses the immune response impacts of multiple pesticide exposure among Brazilian farmers and rural communities near the city of Santo Amaro da Imperatriz. The experimental group consisted of 43 farmers exposed to various pesticide exposures through their work over the course of at least fifteen years. The control group included 30 individuals in the region that did not have occupational exposure to pesticides. “The results of this study show that pro-inflammatory IL-6 [ILs are interleukins, a class of glycoproteins, or cytokine] was significantly elevated in the plasma of farmers compared to that of controls,†say the researchers in this study.
The third study (published in Environmental Toxicology and Pharmacology in 2024) assesses association between organophosphate pesticide exposure and cytokine levels among flower workers in two different Mexican states. There are 143 flower workers who participated in this study. The authors in this study determine that organophosphate exposure decreased pro-inflammatory cytokines and increased one anti-inflammatory cytokines, “suggesting an imbalance of the immune response.†Cytokine imbalance can lead to increased risk of infectious diseases and cancer.
The authors who reviewed these studies also engaged in original research on the impact of chemical mixtures, building on previously published ecotoxicological research. “Unpublished data from our lab indicate that Roundup® (Bayer), a worldwide-used [glyphosate-based herbicide], when combined with Clorpi48 (Huagro) a chlorpyrifos-based insecticide (CbI), adversely impact on human NK [natural killer] cells from healthy donors,†says authors Norberto Walter Zwirner, PhD and Adrián David Friedrich, PhD. “Environmentally relevant exposure doses of these pesticides resulted in a reduced capacity of cytokine-stimulated NK cells [NK cells are a form of lymphocytes that can act as immune system defenders against the spread of microbial infections] to secrete interferon-gamma (IFN-γ). Furthermore, the combination of GbH and CbI impaired the cytotoxic capacity of NK cells against the tumor cell line K562. Regarding the adaptive immune response, our results indicate that the combination of GbH [glyphosate-based herbicides] and CbI [chlorpyrifos-based insecticides] negatively affected T cell proliferation and differentiation in vitro to Th1 cells.â€
The authors conclude, “Altogether, data about the detrimental effects of pesticide mixtures on immune cell functions critical for immunosurveillance are growing and may help explain the increased cancer incidence observed in populations residing in areas exposed to pesticide fumigation.†See yesterday’s Daily News, Pesticides Harming Immune Cell Function Linked to Elevated Breast Cancer Rate in Young Women, for analysis linking immunotoxic impacts of pesticides and heightened risk of breast cancer.
Take Action
For decades, advocates have warned policymakers about the erosion of public trust borne from an inadequate regulatory and sometimes corrupt review process for pesticide products. Look no further than a 2020 press release from CropLife America, the lead U.S. lobbying group representing pesticide manufacturers, in discussing EPA’s “rigorous pesticide Registration Review process†for its proposed interim decision on neonicotinoid insecticides. (See here for public comments by Beyond Pesticides, in collaboration with a coalition of environmental, farmworker, public health, and community groups, on this decision.)
In numerous editions of Pesticides and You—the journal produced by Beyond Pesticides, which provides analyses of breaking public policies, science, and actions relating to pesticide, public health, climate, and biodiversity—there is a clear pattern of failure of federal regulators that permits the poisoning of people, wildlife, and ecosystems.
For easy access to the latest scientific literature dissecting the links between immune system disorders and pesticides, see the Pesticide-Induced Diseases Database.
As the Biden Administration winds to a close, advocates continue to emphasize the importance of local decision making and action in the service of public health, biodiversity, and climate resilience. See the first Action of the Week for 2025 to contact mayors and local elected officials to urge action in transitioning away from toxic petrochemical-based pesticides on public grounds.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources: Frontiers in Immunology
