Indigenous and rural communities are more exposed to harmful pesticides, study finds

A Peruvian study mapping agricultural pesticide mixtures linked to cancer found a strong connection between environmental exposure and increased risk of illness. 

Combining biological research, national cancer registry data, and environmental monitoring, the research team reveals new insights into how pesticide exposure may drive the development of certain cancers.

Pesticides are often found as complex mixtures rather than single substances in food, water, and the environment, therefore making their health impact difficult to measure. In particular, Peru, with its diverse climates and ecosystems, has regions with intensive agriculture and some communities with particularly high levels of pesticides.

The study authors note that prior studies have focused on individual chemicals in controlled settings, which does not reflect how people are exposed in real life. They look closer at the interaction between multiple pesticides and their human impact.

Investigating pesticides

The study, published in Nature Health, found that rural farming communities and Indigenous populations face higher pesticide exposure. Individuals in these groups were, on average, exposed to 12 different pesticides simultaneously.

The research team created a model demonstrating agricultural chemicals spread across the country.The research team created a model demonstrating agricultural chemicals spread across the country. It analyzed 31 commonly used pesticides, none of which were recognized as a known human carcinogen by the WHO.

“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,” details Jorge Honles, Ph.D. in epidemiology at the University of Toulouse, France.

They compared health data from over 150,000 cancer patients between 2007 and 2020 to the exposure maps and found a clear pattern. The regions with higher environmental pesticide exposure had the highest rates of certain cancers, such as gastrointestinal, lung, and skin cancers. In the same areas, the likelihood of developing cancer was on average 150% higher.

“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 at the Pharmacochemistry and Biology for Development laboratory, University of Toulouse.

Global health threats

The authors also stress that pesticide exposure impacts the body before reaching the stage of cancer diagnosis. Tumors can develop in different organs, and some may have biological underlying weaknesses from cellular origins, which may be exacerbated by pesticide exposure.

Climate events such as El Niño may increase the exposure of pesticides and how they travel in the environment.The liver plays a significant role as it processes chemicals entering the body. It also acts as a marker for environmental exposure to pesticides that can interfere with cell function and identity, according to prior Peruvian studies.

These interferences could then accumulate over time and make tissues more vulnerable to other harmful substances.

The authors note that even though the study focuses on Peru, its findings can be applicable on a global scale. Global warming, environmental changes, extreme weather, agricultural practices, and social inequalities all impact health outcomes.

“As global warming advances, these dynamics are likely to intensify, further aggravating the burden of environmentally driven cancers among exposed populations,” stresses the study.

Climate events such as El Niño may increase the exposure of pesticides and how they travel in the environment.

Meanwhile, pesticides commonly used in food crops have been shown to impact beneficial gut bacteria in a prior study. These compounds restrict the bacterial growth studied for their properties in maintaining health. Previously believed to have no effect on bacteria, most of these chemicals are likely to enter the body through food, water, and environmental exposure.

A previous report showed that cereals in Europe contain chemicals at “alarming levels,” as it warned that 81.8% of cereal samples, or 54 out of 66 samples, are contaminated with a trifluoroacetic acid concentration of 78.9 μg/kg on average, which exceeds health safety levels for children and maximum residue limits.