PARIS, FRANCE – October 5, 2025 – Pioneering research by a Franco-Italian team has revealed widespread contamination of clouds over France with pesticides including several chemicals banned in Europe for more than a decade. The study, which for the first time estimated the total quantity of pesticides aloft, suggests that between 6 to 139 tonnes of pesticides are present in low and medium clouds over mainland France.
The team led by chemist Angelica Bianco analysed six cloud water samples collected between 2023 and 2024 at the summit of the Puy de Dôme massif in Auvergne. They detected 32 different pesticides, and shockingly, a third of the samples contained a total pesticide concentration above the regulatory limits for drinking water.
Unprecedented Findings in an Unexplored Matrix
Dr. Bianco, the first author of the study, explained the genesis of the research, noting that while pesticides have long been known to be present in rain and waterways, clouds have remained an “unexplored environmental matrix.” The unique conditions of the Puy de Dôme Observatory, which has a high cloud occurrence 40% of the time) made the study possible.
The novelty of the latest research lies in its rigorous methodology: quantifying pesticides across different seasons, air mass origins (including those that traveled over the Atlantic Ocean), and analyzing 446 different pesticides and their degradation products.
The logistical challenge of cloud sampling is significant. Dr. Bianco noted, “Clouds are event-based: they are not always there!” Using a specialized collector called a “boogie,” researchers limit collection time to less than two hours to ensure the sample is representative of a single air mass, resulting in small, difficult-to-analyze sample volumes.
Long-Distance Transport and Collective Awareness
Dr. Bianco expressed her initial surprise at the findings stating that she was “frankly… hoping not to find pesticides in the clouds.” The first shock was the detection of these compounds in all samples even those where the air mass had traveled at high altitude over the Atlantic Ocean, suggesting long-distance transport.
Though the observed concentrations remain low (in the order of nano to micrograms per litre), the calculation of total mass over France an estimate the researchers reviewers deemed plausible .was the most reactive element of the study.
Dr. Bianco emphasized the environmental significance of the discovery: “This article shows that we have come full circle pesticides are found in river water, lakes, groundwater, rain, and now clouds.” She stresses that the atmosphere is an extremely dynamic transport mechanism, exposing even remote, isolated places like the polar regions to pollution.
The atmosphere and clouds also act as a chemical reactor where sun rays can trigger reactions that degrade these compounds, meaning transformation products are often found alongside the original pesticides.
The research team plans to continue their work by extending the study to a larger number of samples and if possible collecting data from multiple sites to better represent environmental variability. Ultimately Dr. Bianco believes the essential outcome is the “collective awareness of the pollution that we bring into the environment.”