Environmental impact of common pesticides seriously underestimated

(Press-News.org) The environmental impact of nine pesticides, commonly used in grape cultivation, may have been significantly underestimated, suggesting current pesticide risk assessment criteria need updating.

The research will be presented today [Friday 11 July] at the Goldschmidt Conference in Prague.

In laboratory experiments, the nine pesticides that are used in viticulture and on other crops, far exceeded the two-day threshold set by the Stockholm Convention for the half-life of chemicals in the atmosphere. The researchers also identified several unknown molecules when they looked at how the pesticides break down and degrade in the atmosphere.

Global use of pesticides has doubled since 1990, according to the UN Food and Agriculture Organisation, raising concerns about the potential impact on health and the environment. In light of their new findings, the research team argues that regulatory frameworks governing the human and environmental safety of these pesticides should be urgently updated.  

Pesticides enter the atmosphere in particular when sprayed onto crops, leading to air pollution. As semi-volatile compounds, their molecules can be present in the atmosphere in several forms – either as a gas or vapour (gas phase), or as particles (particulate phase). In the particulate phase, they are adsorbed onto the surface of airborne particles, like dust or organic matter suspended in the air. This adsorption can lead to longer half-lives, meaning they take longer to break down and can travel further.

European regulations currently only consider the atmospheric lifetimes of pesticides based on their gas phase. If a pesticide is shown to have an atmospheric half-life of more than two days, it is considered prone to long-range atmospheric transport, which is a key factor in classifying it as a persistent organic pollutant.

In their study, Boulos Samia and colleagues at Aix-Marseille University and CNRS, France, investigated the atmospheric half-lives of nine pesticides commonly used in viticulture – growing and harvesting of grapes. They adsorbed the pesticides onto atmospheric particles and exposed them to ozone and hydroxyl radicals – to simulate how they would behave in the earth’s lower atmosphere – or troposphere.

They reveal that none of the compounds has a half-life within the two-day limit set by Stockholm convention: instead, they ranged from three days (Cyprodinil) to over a month (Folpet). This suggests all nine compounds could be reclassified as persistent organic pollutants – far more harmful and persistent than previously thought.

Boulos Samia says: “These pesticides are used in huge quantities across Europe and our research shows limited understanding about how they endure in the lower atmosphere. In the past they have been studied in their gas phase, and this is how EU regulations are set. Yet our research shows they are far less reactive in their particulate phase, meaning that they degrade more slowly. Because of this, they should be considered as persistent organic compounds with potential for long-range transport, and that the models used to test their safety do not go far enough”

In a second experiment, the team studied the degradation mechanisms of their pesticides, observing several toxic and non-commercially available molecules. This suggests further study is needed to appropriately assess the toxicity of these pesticides.

Finally, they looked at how temperature and relative humidity affect the partitioning of the pesticide molecules between gas and the particle phase, finding discrepancies compared with current models of their behaviour.

Boulos Samia continues: “Together these experiments suggest that pesticides used in agriculture need updated regulatory frameworks that take into account their particulate phase behaviour in the atmosphere.”

The Goldschmidt Conference is the world’s foremost geochemistry conference. It is a joint congress of the European Association of Geochemistry and the Geochemical Society (US) and over 4000 delegates attend. It takes place in Prague, Czech Republic, from 6-11 July 2025.

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