Pesticide exposure is associated with increased cancer risk and early cellular disruption, especially in heavily exposed communities, calling for new approaches to health risk evaluation.
A new study published in Nature Health reports a strong association between environmental exposure to agricultural pesticides and an increased risk of cancer. Researchers from the IRD, Institut Pasteur, the University of Toulouse, and the National Institute of Neoplastic Diseases (INEN) in Peru combined environmental data, a nationwide cancer registry, and biological analysis to better understand how pesticide exposure may contribute to certain cancers.
Pesticides are commonly found in food, water, and the environment, often as mixtures of multiple chemicals. Studying their health effects has been challenging because most research focuses on single substances under controlled conditions that do not reflect real-world exposure. This study takes a broader approach by examining how combined exposures affect populations in everyday settings.
In Peru, agricultural intensity varies widely across regions, alongside diverse climates, ecosystems, and significant social inequalities. Cancer is now a major public health concern, and pesticide contamination is widespread. The findings show that some groups, especially Indigenous and rural communities, face higher exposure. On average, these populations are exposed to 12 different pesticides at elevated levels at the same time.
Nationwide Modeling of Pesticide Pollution
The researchers developed a national model to identify areas with the highest levels of pesticide-related environmental contamination. The model included 31 agricultural chemicals, none classified as known human carcinogens by the World Health Organization (WHO), and tracked how they spread across the country.
“We first modeled the dispersion of pesticides in the environment over a six-year period, from 2014 to 2019, which allowed us to create a high-resolution map and identify areas with the highest risk of exposure,” explains Jorge Honles, PhD in epidemiology at the University of Toulouse.
The team then compared this exposure map with geospatial data from more than 150,000 cancer patients diagnosed between 2007 and 2020. This analysis revealed regions where both pesticide exposure and cancer rates were higher. In these areas, the likelihood of developing cancer was about 150% greater on average.
Biological Evidence and Tumor Vulnerability
“This is the first time we have been able to link pesticide exposure, on a national scale, to biological changes suggesting an increased risk of cancer,” explains Stéphane Bertani, a researcher in molecular biology at the French National Research Institute for Sustainable Development (IRD), at the PHARMA-DEV laboratory (IRD/University of Toulouse).
The findings show that different types of tumors may share underlying biological weaknesses tied to their cellular origins, which can be affected by pesticide exposure. The liver plays a key role because it processes chemicals and acts as an early indicator of environmental exposure. Molecular studies at the Institut Pasteur, led by Pascal Pineau, found that pesticides interfere with processes that maintain normal cell function and identity.
These disruptions can occur before cancer develops, indicating early and gradual effects that may go unnoticed. Over time, they could make tissues more susceptible to other risks, including infections, inflammation, and environmental stress.
Rethinking Risk Assessment and Global Implications
The results challenge traditional toxicology, which typically evaluates individual chemicals and sets safety thresholds based on isolated exposure. Instead, the study highlights the need to consider combined exposures, environmental conditions, and real-world social factors. It also suggests that events such as El Niño may increase exposure by changing how pesticides are used and distributed in the environment. The findings support revisiting current risk assessment and prevention strategies.
While focused on Peru, the research contributes to a broader understanding of global health and environmental limits. It shows how environmental change, unsustainable land use, extreme weather, and social inequality can interact to impact human health, especially among vulnerable populations such as Indigenous and rural communities.
The research team plans to continue studying the biological mechanisms involved and to develop better tools for prevention, with the goal of supporting more equitable and effective public health policies.
Reference: “Mapping pesticide mixtures to cancer risk at the country scale with spatial exposomics” by Jorge Honles, Juan Pablo Cerapio, Claudia Monge, Agnès Marchio, Eloy Ruiz, Ramiro Fernández, Sandro Casavilca-Zambrano, Juan Contreras-Mancilla, Tatiana Vidaurre, Thomas Condom, Swann Zerathe, Olivier Dangles, Éric Deharo, Javier Herrera-Zuñiga, Pascal Pineau and Stéphane Bertani, 1 April 2026, Nature Health.
DOI: 10.1038/s44360-026-00087-0
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