Long-Term Air Monitoring Shows Pesticides Aren’t Gone—They’re Coming Back

Persistent pesticides continue to pollute our air decades after their ban, a new long-term study at the Czech National Atmospheric Observatory reveals. Researchers found that concentrations of legacy organochlorine pesticides (OCPs) have stopped declining and remain in the environment due to secondary sources like soil, while some current-use pesticides (CUPs) linger in the atmosphere years after prohibition. These findings underscore the urgent need for continuous monitoring and stricter measures to protect human health and ecosystems.  

“We looked into the atmospheric levels of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) over the years, at an agricultural site in the Czech Republic. A few things stood out, for instance, concentrations of some OCPs declines over time, we found that concentrations of key pollutants like β- and γ-HCH, DDT , α-chlordane, and mirex are leveling off, which means that secondary sources, such as soil and bodies, are enhanced and release these pollutant s back to the environment over time, especially in the summer,” says main author of the publication Ludovic Mayer.

The researchers also observed that CUPs atmospheric levels mostly decreased or showed no significant changes over time, but critically, banned substances like chlorpyrifos and fenpropimorph remained detectable in the atmosphere even years after their bans took effect, highlighting their persistence.

“Our research is vital because it challenges the assumption that highly persistent banned substances disappear naturally over time; the leveling off of OCPs  concentrations proves that decades-old pollution sources continue to contaminate our air, posing ongoing risks to human and environmental health. We established that environmental loads of these semivolatilecompounds persist because they degrade much slower in soils and have the capacity to revolatilise over time,” adds Ludovic Mayer.

Moreover, tracking current-use pesticides provides immediate feedback on the effectiveness of recent bans, showing that compounds like chlorpyrifos and fenpropimorph persist in the atmosphere years after they were prohibited, indicating a need for continued vigilance regarding environmental clearance and human exposure to these toxic substances. The study highlights the importance of continued long-term monitoring for CUPs, which is currently lacking, but would provide sufficient insights into their atmospheric fate and to develop accurate models to predict key environmental processes like transport and deposition.

The conclusions were reached by performing continuous biweekly air sampling at the National Atmospheric Observatory Košetice (NAOK), a rural-agricultural site in the Czech Republic, spanning 10 years for OCPs and three years for CUPs.  

“We collected air samples with large air pumps that pull outdoor air through special filters, allowing us to capture both airborne particles and the pesticides that exist as gases. In the lab, we used sensitive instruments to identify and measure these pesticides very precisely. We then applied statistical methods to see how pesticide levels changed over the years and how factors like temperature affected their release back into the air from surfaces such as soil.

These findings help us better understand how pesticides behave in the environment, and they show why long-term monitoring is essential. In the future, we hope to study a wider range of chemicals and also look at the interaction, not just with air, but in soil, water, and rain/snowfall. That way we can get a clearer picture of the cycling of those compounds in the environment,” concludes Ludovic Mayer. 

The original article

Current-use and legacy pesticides' multi-annual trends in air in central Europe: primary and unidentified secondary sources

Ludovic Mayer, Lisa Melymuk, Adela Holubová Šmejkalová, Jiři Kalina, Petr Kukučka, Jakub Martiník, Petra Přibylová, Petr Šenk, Pourya Shahpoury, and Gerhard Lammel

Atmos. Chem. Phys., 25, 12467–12482

 https://doi.org/10.5194/acp-25-12467-2025

licensed under CC-BY 4.0

Abstract

This study investigated 48 current-use pesticides (CUPs) and 30 organochlorine pesticides (OCPs) in ambient air at a rural-agricultural site in the Czech Republic, with biweekly sampling over three and 10 years, respectively. Despite being banned decades ago, OCPs persist in the atmosphere, with revolatilisation from surfaces apparent in summer. Temporal trend analysis revealed decreasing atmospheric concentrations for several OCPs, which indicate long-term diminishing reservoirs in environmental compartments, especially soil. For β- and γ-HCH, - and -DDE, -DDD, - and -DDT, α-chlordane, and mirex, levelling off is observed, which points to recently enhanced secondary sources in the region or beyond, related to reversal of the direction of air-surface exchange in response to historic atmospheric depositions or recent mobilisation from ground compartments, such as water bodies, the cryosphere, or soils heated by wildfires.

CUP concentrations peaked during application seasons, with multi-annual trends either insignificant or declining. For compounds like chlorpyrifos and fenpropimorph, declining trends aligned with regulatory bans, though their presence in the atmosphere was evident one-year after the bans, suggesting persistence.

2 Methodology

2.4 Sample preparation and analysis 

Air samples were first spiked with isotopically-labelled standards (Table S3) and then underwent extraction using an automated extractor (E-800, Büchi Extraction System, Flawil, Switzerland), with 150 mL of methanol and 5 mM of ammonium acetate for CUPs and 150 mL of dichloromethane for OCPs. CUPs extract clean-up was done by filtration through a 0.22 µm pore size cellulose acetate membrane (Corning Costar Spin-X, United States) and concentrated under a gentle stream of nitrogen to a final volume of 500 µL. 100 µL of MilliQ water were then added to a 100 µL aliquot of the extract which was then used for analysis. After extraction, OCPs extracts were transferred to a glass column (30 mm i.d.) filled with 0.5 g of activated silica, 30 g of H2SO4 modified activated silica and 1 g of non-activated silica and were eluted with 40 mL of DCM:hexane (1:1). 50 µL of n-nonane was added as a keeper solvent, and the extract was then concentrated under a gentle stream of nitrogen to a final volume of 100 µL.

CUPs were analysed using a high-performance liquid chromatograph (HPLC, Agilent 1290, Agilent, Santa Clara, USA) coupled to a mass spectrometer (QTRAP 5500, AB Sciex, Framingham, USA) using four different methods previously developed and described (Mayer et al., 2024). The precursor to product ions were monitored in scheduled multiple reaction monitoring mode (MRM) (Table S4). The identification of individual pesticides was based on the comparison of intensity ratios of ions and retention times with standards and quantification was done using internal calibration with isotopically labelled standards (Table S4).

OCPs were analysed by gas chromatography-mass spectrometry (GC-MS/MS). Analysis realised with 7890A GC coupled to a triple quadrupole 7000B MS for 2015-2017 samples then 8890 GC coupled to a triple quadrupole 7000D MS for 2018-2022 samples.