Protecting farmers’ eyes from pesticides
28 Mar 2024
- Orla Fernie



Researchers from University of Manchester and Syngenta visited our OFFSPEC beamline to investigate the interaction between pesticides and corneal cell membrane which results in irritation of the eye. 




Pesticides are widespread in the agriculture industry to minimise the effects of weeds, pests and diseases on crops. Debates about costs to wildlife and their environmental impact are common, but the health impact on the farmers using the pesticides is rarely considered. This study delved into this issue, observing how surfactants responsible for the irritation interact with the eye.   

Commercial pesticides are often formulated as emulsifiable concentrates with nonionic surfactants. Nonionic surfactants consist of an uncharged hydrophilic head group and hydrophobic tail. In pesticides, they re-disperse the formulation in the spray tank, help reduce bouncing of spray droplets on leaf surfaces and can ​improve pesticide uptake into the desired plant by influencing solubility and mobility. However, when these nonionic surfactants come into contact with users' eyes, it can cause irritation. Thus, there is a need to understand how nonionic surfactants irritate corneal cells to help the agrochemical industry design safer pesticides while maintaining benefits on leaf dispersal.   

The focus of this study was the impact of surfactants on changes in the membrane nanostructure and composition. Both natural and model cell membranes were used in this study, the nanostructures of which were analysed upon exposure to nonionic surfactants. Techniques included insertion of nonionic surfactants into lipid membranes by quartz crystal microbalance with dissipation (QCM-D), dual polarization interferometry (DPI), confocal laser scanning microscopy (CLSM), and neutron reflection (NR) performed on our OFFSPEC beamline.  



The cart​oon schematic shows different surfactant-lipid bilayer interactions observed. Surfactants with well-balanced hydrophobicity accumulate in the lipid bilayer of the cell. Highly hydrophobic surfactants cannot break the lipid hydrophilic head boundary (resulting in weak structural impact) and hydrophilic surfactants are only inserted into the membrane a small amount.  

The surfactants tested varied in hydrophobicity and therefore have differing interactions with the membrane (depicted in the schematic). Hydrophobically balanced surfactants elicit large cytoplasm leakage by damaging the membrane. When increasing or decreasing the hydrophobicity of the surfactants, the researchers observed reduced membrane disruptive ability. Surfactants that are highly hydrophilic or hydrophobic elicit less structural changes and cell death is not immediately caused by cytoplasm leakage, but rather occurs over a longer period due to membrane leakage.   

The researchers hope that these findings, and information on the physiochemical properties such as membrane leakage and permeability will provide a basis for reduction of the eye irritation potential of pesticide industrial formulations.  

Contact: Fernie, Orla (STFC,RAL,ISIS)