A study presented on Friday, July 11, at the Goldschmidt Conference in Prague reveals that the environmental impact of nine commonly used pesticides in grape cultivation may be severely underestimated, indicating that current pesticide risk assessment standards urgently need updating.
In laboratory experiments, the residues of nine pesticides used in viticulture and other crops far exceeded the two-day atmospheric half-life threshold for chemicals specified in the Stockholm Convention. While observing how these pesticides decompose and degrade in the atmosphere, researchers also discovered several unknown molecules. According to data from the Food and Agriculture Organization of the United Nations, global pesticide use has doubled since 1990, raising concerns about the potential effects of pesticides on health and the environment. Based on these new findings, the research team believes that updating the regulatory framework for managing the safety of pesticides for humans and the environment is now urgent.
After being sprayed on crops, pesticides enter the atmosphere and cause air pollution. As semi-volatile compounds, pesticide molecules can exist in the atmosphere in various forms such as gas or vapor (gas phase) and particles (particle phase). In the particle phase, pesticides are adsorbed onto the surface of airborne particulate matter, such as dust or organic matter, which prolongs their half-life, resulting in longer decomposition times and greater transport distances.
Current European regulations only consider the atmospheric lifetime of pesticides based on their gas phase. If a pesticide's atmospheric half-life exceeds 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 this study, Boulos Samia from Aix-Marseille University and the French National Centre for Scientific Research, along with colleagues, investigated the atmospheric half-lives of nine pesticides commonly used in grape cultivation. They adsorbed the pesticides onto atmospheric particulate matter and exposed them to ozone and hydroxyl radicals to simulate their behavior in the lower atmosphere (troposphere). The results showed that none of the compounds reached the two-day limit set by the Stockholm Convention; instead, their half-lives ranged from three days (for cyprodinil) to more than a month (for captan). This indicates that all nine compounds should be reclassified as persistent organic pollutants, with hazards and persistence far exceeding previous understanding.
Samia stated that these pesticides are widely used in Europe, but there is limited knowledge about their residues in the lower atmosphere. Previous studies have mostly focused on their gas-phase state, and EU regulations are also based on this. However, the research shows that they exhibit low reactivity and slow degradation in the particle phase, and should be regarded as persistent organic compounds with potential for long-range transport. Existing safety testing models are insufficient.
In a second experiment, while studying the degradation mechanisms of pesticides, the research team observed several toxic and non-commercial molecules, indicating that further research is needed to accurately assess the toxicity of these pesticides. In addition, they examined the effects of temperature and relative humidity on the partitioning of pesticide molecules between the gas and particle phases, finding differences from current behavior models.
Samia said that these experiments collectively demonstrate that pesticides used in agriculture require an updated regulatory framework that fully considers their particle-phase behavior in the atmosphere. This study provides a new perspective and basis for pesticide regulation. How to improve the regulatory framework accordingly to ensure agricultural production and environmental safety will become the focus of future attention.
