How Different Formulas and Additives Affect Pesticide Residue on Plant Leaves

Jenn Hoskins
14th June, 2024

How Different Formulas and Additives Affect Pesticide Residue on Plant Leaves

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at the University of Hertfordshire found that the type of pesticide formulation significantly impacts residue levels on crops
  • Wettable powder formulations retained lower residue levels on tomato plants compared to emulsifiable concentrate formulations
  • Adding adjuvants generally did not affect residue levels, except for a specific reduction in French beans treated with an emulsifiable concentrate and TEHP
Understanding the risks associated with pesticide exposure is critical for both regulatory bodies and public health. Traditionally, risk assessments focus on estimating the residue that can be transferred from plant foliage to skin or clothing, known as dislodgeable foliar residues (DFRs). However, the availability of DFR data is limited due to the high cost and seasonal constraints of these studies. A recent study conducted by researchers at the University of Hertfordshire[1] sheds new light on this issue by examining how pesticide formulations and adjuvants affect DFR on various crops. The study specifically investigated the active substance difenoconazole, applied as an emulsifiable concentrate (EC 10%) and a wettable powder (WP 10%), with and without the addition of adjuvants Tween 20 and organophosphate tris(2-ethylhexyl)phosphate (TEHP). The crops studied included tomato, French bean, and oilseed rape. The results demonstrated that the type of formulation significantly impacts DFR levels. For instance, on tomato plants, the WP formulation retained a lower DFR percentage (39 ± 4.7%) compared to the EC formulation (60 ± 1.2%). Interestingly, the addition of adjuvants generally did not significantly affect DFR levels, except in the case of French beans treated with EC and TEHP, which showed an 8% reduction in DFR compared to the EC formulation alone. These findings align with earlier research highlighting the complexities of pesticide formulations and their potential impacts on toxicity and exposure. For example, a study on glyphosate-based formulations revealed that adjuvants, often considered inert, could significantly increase toxicity[2]. This earlier research demonstrated that formulations containing ethoxylated adjuvants were more toxic to human cells than glyphosate alone, challenging the notion that only the active ingredient determines toxicity. Moreover, the new study's findings are consistent with the broader understanding that pesticide formulations can influence environmental and biological interactions. Previous research has shown that inert ingredients can enhance the environmental mobility and persistence of pesticides, thereby increasing exposure risks[3]. This underscores the importance of assessing full pesticide formulations, rather than just the active ingredients, to obtain a comprehensive understanding of their risks. The University of Hertfordshire study also offers practical implications for regulatory agencies. Given the variability in DFR based on formulation and crop type, regulatory bodies might need to reconsider their reluctance to extrapolate study data across different scenarios. This could lead to more nuanced and accurate risk assessments, ultimately improving public health protections. In conclusion, the new laboratory technique employed in this study provides a valuable tool for investigating the role of pesticide formulations and adjuvants in DFR levels. By demonstrating that these factors can significantly influence residue transfer, the research supports the need for more comprehensive evaluations of pesticide formulations. This study not only builds on existing knowledge but also challenges regulatory practices, advocating for a more holistic approach to pesticide risk assessment.

AgricultureEnvironmentBiochem

References

Main Study

1) The effect of formulation composition and adjuvant type on difenoconazole dislodgeable foliar residue.

Published 13th June, 2024

https://doi.org/10.1080/03601234.2024.2361595

Related Studies

2) Ethoxylated adjuvants of glyphosate-based herbicides are active principles of human cell toxicity.

https://doi.org/10.1016/j.tox.2012.09.006

3) Unidentified inert ingredients in pesticides: implications for human and environmental health.

Journal: Environmental health perspectives, Issue: Vol 114, Issue 12, Dec 2006


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