Hidden Danger: Widely Used Pesticides Linked to 150% Higher Cancer Risk

Researchers have identified a link between widespread pesticide exposure and cancer risk, driven by subtle biological changes that emerge long before diagnosis.

A sweeping new study in Nature Health is reshaping how scientists think about pesticide exposure, pointing to a strong connection between everyday environmental contact with these chemicals and a higher risk of cancer.

By combining environmental monitoring, national cancer registry data, and biological analyses, 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 certain cancers.

Pesticides are commonly found in food, water, and the broader environment, often as complex mixtures rather than single compounds. This has made their health effects difficult to measure, since most previous research has focused on individual chemicals under controlled conditions that do not reflect everyday exposure. This study takes a more comprehensive approach, capturing the complexity of real-world conditions.

Peru, a Relevant Study Site

Peru offers a unique setting due to its mix of intensive farming regions, diverse ecosystems, and pronounced social and geographic inequalities. Cancer has become a growing public health concern, alongside rising pesticide exposure.

The findings show that certain populations, especially Indigenous and rural communities, face higher exposure levels. On average, these groups encounter 12 different pesticides at elevated concentrations.

An innovative method linking environment, biology, and cancer

Researchers created detailed models to map pesticide pollution across the country. The analysis included 31 agricultural chemicals, none of which are currently classified as known human carcinogens by the World Health Organization (WHO), and tracked how they spread through the environment.

“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 maps with geolocation data from more than 150,000 cancer cases recorded between 2007 and 2020. This revealed regions where both pesticide exposure and cancer rates were higher. In these areas, the likelihood of developing cancer was about 150% greater.

“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 found that some tumors share underlying biological weaknesses tied to their cellular origins, which pesticide exposure may aggravate. The liver plays a central role, as it processes chemicals and often reflects environmental exposure.

Further molecular studies at the Institut Pasteur, led by Pascal Pineau, show that pesticides interfere with systems that maintain normal cell function and identity. These disruptions can occur long before cancer develops, indicating gradual and often unnoticed effects. Over time, such changes may leave tissues more susceptible to additional risks like infection, inflammation, or environmental stress.

Major implications for global health and cancer prevention

The findings challenge traditional toxicology, which typically evaluates single substances and defines safety thresholds based on isolated exposure. Instead, the study emphasizes the need to consider combined chemical exposures and real-life environmental conditions. It also suggests that events such as El Niño may increase exposure by changing how pesticides are used and dispersed. The authors call for updated risk assessment methods and prevention strategies.

Beyond Peru, the study contributes to a broader conversation about global health and environmental limits. It highlights how environmental change, land use practices, extreme weather, and social inequality can interact to shape health outcomes, particularly for vulnerable populations such as Indigenous and rural communities.

The research team plans to continue investigating the biological mechanisms involved and to develop better tools for prevention, with the goal of supporting more effective and equitable public health policies.