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

Rigorous risk assessments for those exposed to pesticides are carried out to satisfy crop protection regulatory requirements. Non-dietary risk assessments involve estimating the amount of residue which can be transferred from plant foliage to the skin or clothes, known as dislodgeable foliar residues (DFRs). DFR data are less available than crop residue data as studies are costly and limited by seasonality. European regulatory authorities are reticent to allow extrapolation of study data to different scenarios as the contributory factors have hitherto been poorly identified. This study is the first to use a new laboratory DFR method to investigate how one such factor, pesticide formulation, may affect DFR on a variety of crops. The study used the active substance difenoconazole as both an emulsifiable concentrate (EC 10%) and a wettable powder (WP 10%) with and without adjuvants (Tween 20 and organophosphate tris(2-ethylhexyl)phosphate TEHP) on tomato, French bean and oilseed rape. A comparable DFR% was retained from the WP and EC formulation on most crops except for tomato, where lower DFR% was retained in the case of WP (39 ± 4.7%) compared to EC (60 ± 1.2%). No significant effect of adjuvant addition was observed for either formulation except when mixing TEHP (0.1% w/v) to the EC 10% on French bean, resulting in 8% DFR reduction compared to the EC formulation alone. This research demonstrates the value of a unique DFR laboratory technique in investigating the importance of the formulation and in-tank adjuvants as factors that affect DFR.

A new laboratory method to study the impact of leaf texture on pesticide dislodgeable foliar residues (DFR).

Pesticides are vital in meeting the challenge of feeding the rapidly increasing world population. However, it is crucial that they are used in a way that does not compromise the safety of humans or the environment. Non-dietary worker risk assessments consider the amount of residue which can be transferred from plant foliage to the skin or clothes, known as dislodgeable foliar residues (DFRs). DFR data scarcity due to the costly and seasonal characteristics of DFR studies is an obstacle to the extrapolation of DFR data to different crops/leaves. This paper validates a new proof-of-concept technique to investigate factors that may affect DFR (leaf texture) using the fungicide difenoconazole EC 10% as an example on various leaves (i.e., French bean, soybean, tomato, oilseed rape, and wheat). DFR was the lowest in the case of oilseed rape (31.0 ± 3.4%) and the highest in French beans (82.0 ± 2.9%). This significant difference in DFR in the findings of this study sheds light on the importance of the leaf surface as a major factor affecting DFR and supports the application of the laboratory method for more extensive data generation. More data generation would enable the extrapolation saving money and resources.

Correlation between dietary and dislodgeable foliar (DFR) crop residues decline data; A proposed approach to refine non-dietary risk assessment.

Pesticide residues in crop plants are routinely measured in an edible commodity or in feed items to determine safe use. Pesticides present as dislodgeable foliar residues (DFR) are measured for use in non-dietary risk assessments where worker, resident and bystander re-entry may lead to contact with the treated foliage. Possible correlations between dietary and DFR residue decline have been investigated considering data from 177 dietary residue trials along with 56 DFR trials from outdoor studies on the same crops besides residue decline data available in the Plant Properties Database (PPDB).The residue studies proved to follow the non-normal distribution and the comparison between DT50 of both types of residues for all the active substances revealed higher numerical DT50 mean values of the dietary residue compared to the DFRs. The dissipation from dietary residue studies is slower with a higher population mean compared to the mean for DFR studies for most active substances studied. A DT50 value from dietary residue studies could potentially act as a conservative surrogate DT50 for DFR which could be useful in determining the length of DFR studies and benefit both the agrochemical industry and the regulatory bodies in supporting non-dietary pesticide risk assessment.

Development of a New Dislodgeable Foliar Residue Analytical Laboratory Method for Pesticides.

The dislodgeable foliar residue (DFR) is the amount of pesticide that exists on foliage after the pesticide has dried and which could dislodge to the skin or clothes of workers and is a key parameter for non-dietary risk assessments required to demonstrate safe use for pesticide registration. DFR data in the literature are described as insufficiently reliable, limited, and encompasses considerable statistical uncertainties. The purpose of this article is to describe a newly developed laboratory method for the quantification of DFR with an illustrative example. The laboratory method reflected available field DFR methodology but involved controlled application of droplets to leaves and validation of the wash-off process used to remove the residue from the leaf surface before the analytical quantification. A very high level of accuracy (99.7-102.1%) and precision (±1.5%) was achieved. Residue data generated from the illustrated application of the method showed a robust normal distribution, unlike field studies. The method is deemed to be controllable, cost-efficient, and time-saving, taking hours rather than days. This enables the generation of more data to allow extrapolation between the generated data by investigating multiple factors that may influence DFR. An improved understanding of DFR could save time, money, and resources.