Exposure Assessment of Airborne Endotoxin, Glyphosate Residues, and Particles in Farms During Summer Spray Season

Many low–molecular weight chemicals including some pesticides and herbicides are capable of inducing occupational asthma. Glyphosate [(N–phosphonomethyl) glycine] is one of the most commonly used broad spectrum nonselective herbicides in the world. Glyphosate application was associated with asthma and rhinitis in large-scale epidemiological studies of US farmers and a possible role of glyphosate in airway inflammation was previously shown in our laboratory study. Levels of airborne endotoxin and dust particles in farm environments are typically high as well. The cumulative exposures to endotoxin, glyphosate residues, and dust particles in farms could be associated with airway inflammation and asthma among farmers. In this field study, we have examined parallel exposure levels of airborne endotoxin, glyphosate residues, and particles of different sizes in several large corn farms of U.S.A. during summer glyphosate spray seasons. Samples were collected by conventional and non-conventional size-selective aerosol sampling/source testing methods (for aerosolizable contaminants from ground surface) before and during/after spraying. Extracts of aerosol samples were analyzed for endotoxin and glyphosate by Limulas amebocyte lysate assay and glyphosate-specific ELISAs. Higher levels of endotoxin and glyphosate were observed in >1.8 µm particle size fractions and total inhalable aerosols compared to other particle size fractions. Endotoxin levels in air were found to be same during pesticide spray and in control samples. Reaerosolizable glyphosate residues and endotoxin on farm soil surfaces after spray were mostly below the detection limits. Glyphosate spraying in all farms increased particle concentrations for all sizes (0.3 - >20 µm), however, the increasing trends were more prominent for particles of >3 µm sizes.