Background: The US EPA recently withdrew its Interim Registration Review Decision for glyphosate because of its uncertain carcinogenic effects; but the cumulative respiratory health effects of this herbicide along with airborne bacterial endotoxin cannot be ruled out. This study investigated particle size-selective exposure levels of airborne endotoxin and glyphosate in agricultural farms and estimated their deposition levels in different respiratory tract regions.

Methods: Air samples were collected by size-selective aerosol sampling methods before and after or during the pesticides spraying periods. Extracts of aerosol samples were analyzed for endotoxin and glyphosate by Limulas amebocyte lysate assay and specific ELISAs. The multiple-path particle dosimetry model (MPPD-V3.04) was used to calculate the deposited dose at three respiratory tract regions, given the exposure scenario of a standard worker and concentrations of these two contaminants at 1 – 1.8 µm particle fractions. The data were further utilized for the baseline information on the selection of a proper respiratory personal protective equipment (PPE).

Results: Relatively high exposure levels of glyphosate and endotoxin were observed in particulate form (e.g., Button sampler data for glyphosate and endotoxin were 19.08±13.06 ng/m³ and 7.61±5.36 EU/m³ in pesticide treated farms, respectively). Control farms had lower airborne glyphosate levels, mostly below the limits of detections. Levels of glyphosate deposition fractions at head airways, tracheobronchial, and pulmonary regions were 0.127 – 0.22, 0.05 – 0.06, and 0.127 – 0.17, respectively.

Conclusions: Total inhalable exposure levels to airborne endotoxin and glyphosate were relatively low, but, higher levels of pulmonary depositions were observed in size-fractionated samples and chronic exposures to these contaminants at lower respiratory tract could cause adverse health effects to agricultural workers. Our findings provide a reference for industrial hygiene researchers to initiate appropriate control strategies to reduce the exposure levels encountered by workers, such as the use of proper respiratory PPE.