A major new study published in Nature Health has found a strong connection between environmental exposure to agricultural pesticides and an increased risk of cancer. By combining environmental monitoring, national cancer registry data, and biological research, scientists from the IRD, Institut Pasteur, University of Toulouse, and the National Institute of Neoplastic Diseases (INEN) in Peru provide new insight into how pesticide exposure may contribute to the development of certain cancers.
Pesticides are commonly found in food, water, and the surrounding environment, often as complex mixtures rather than single substances. This has made their health effects difficult to measure. Most previous research has focused on individual chemicals in controlled settings, which does not reflect how people are exposed in real life. This new study takes a broader approach, examining how multiple pesticides interact and affect populations under real-world conditions.
Why Peru Was Chosen for the Study
Peru offers a unique setting for this type of research. The country includes regions with intensive agriculture, diverse climates and ecosystems, and significant social and geographic inequalities. Cancer is an increasing public health concern, and pesticide exposure levels in some communities are particularly high.
The findings show that certain populations, especially Indigenous and rural farming communities, face higher exposure. On average, individuals in these groups are exposed to around 12 different pesticides at elevated concentrations at the same time.
Mapping Pesticide Exposure and Cancer Risk
To better understand the link between pesticides and cancer, researchers created detailed models showing how agricultural chemicals spread across the country. The analysis included 31 widely used pesticides. None of these are classified as known human carcinogens by the World Health Organization (WHO), yet their combined presence in the environment was carefully tracked.
“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 these exposure maps with health data from more than 150,000 cancer patients recorded between 2007 and 2020. This comparison revealed a clear pattern. Regions with higher environmental pesticide exposure also had higher rates of certain cancers. In these areas, the likelihood of developing cancer was about 150% greater on average.
“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).
Early and Silent Biological Effects
The research also highlights how pesticide exposure may affect the body long before cancer is diagnosed. Although tumors can develop in different organs, some share underlying biological weaknesses tied to their cellular origins. These vulnerabilities may be influenced by pesticide exposure.
The liver plays a key role because it processes many chemicals entering the body and acts as a marker for environmental exposure. Molecular studies conducted at the Institut Pasteur, led by Pascal Pineau, show that pesticides can interfere with processes that maintain normal cell function and identity. These disruptions occur early and may accumulate over time without obvious symptoms.
Such changes could make tissues more susceptible to other harmful influences, including infections, inflammation, and environmental stress.
Implications for Health Policy and Risk Assessment
The findings challenge traditional approaches to chemical safety, which typically evaluate one substance at a time and define exposure limits considered safe. This study suggests that these methods may overlook the risks posed by combined exposures and real-life environmental conditions.
It also points to the role of external factors such as climate events. Phenomena like El Niño may increase exposure by affecting how pesticides are used and how they move through the environment. The researchers argue that current risk assessment and prevention strategies need to be updated to reflect these complexities.
A Broader Global Health Concern
While the study focuses on Peru, its implications extend worldwide. It highlights how environmental changes, agricultural practices, extreme weather, and social inequalities can interact to influence health outcomes. Vulnerable populations, including Indigenous and rural communities, may face the greatest risks.
The research team plans to continue investigating the biological mechanisms involved and to develop better tools for prevention. Their goal is to support more effective and equitable public health policies that account for real-world environmental exposures.
