Atmospheric transport of particulate matter and particulate-bound agrochemicals from beef cattle feedlots: human health implications for downwind agricultural communities

Abstract

Background Beef cattle feedlot–derived particulate matter (PM) is a complex mixture of dust, animal waste, agrochemicals, and bioaerosols. No empirical data currently exists quantifying human exposure of PM–bound agrochemicals downwind of feedlots. Objectives There were three objectives of the current study: 1) to determine spatial extent and magnitude of PM transport downwind of large beef cattle feedlot facilities, 2) to quantify occurrence of pyrethroid insecticides and anthelmintics in feedlot–derived PM, and 3) to assess cumulative human health risk of agrochemicals in agriculture–adjacent communities downwind of feedlots. Methods Authors investigated downwind transport (<1 to >12 km) of total suspended particulates (TSP) from three feedlots in the Southern Great Plains (SGP) of North America. PM collected on TSP filters was analyzed via UHPLC–MS/MS for six pyrethroids (bifenthrin, λ–cyhalothrin, cypermethrin, esfenvalerate, fenvalerate, and permethrin) and five macrocyclic lactones (MLs; abamectin, doramectin, eprinomectin, ivermectin, and moxidectin). An empirical distance decay model was used to determine probabilistic PM concentrations in downwind ambient air. Results Downwind TSP concentrations exhibited rapid decline from 0.01 – ≤1.6 km (Monte Carlo–simulated mean ± SEM; 5,049 ± 96.1 μg/m3) and subsequent stabilization >1.6 – 12.4 km (1,791 ± 9.9; μg/m3). TSP concentrations did not converge to background levels within the spatial extent of the study (12.4 km). Agrochemicals were detected downwind >LOQ at greater overall frequency (40.6%) than upwind locations (26.8%). Two pyrethroids were detected at the highest overall downwind concentrations (mean ± SEM; fenvalerate = 5.9 ± 0.8, permethrin = 1.1 ± 0.3 ng/m3), and screening–level cumulative exposure estimates indicate elevated pyrethroid risk (LOC = 1; RI = 0.173) in children (1–2 yrs) living near commercial agricultural operations in the SGP. Discussion Results significantly expand the known distribution of feedlot–derived PM and agrochemicals, and consequently highlight exposure pathways unrecognized in residential human health assessments and feedlot risk evaluations.