Atmospheric transport and deposition of particulate matter and particulate-bound agrochemicals from beef cattle feedlots: Implications for human health and ecological risk assessment

Beef cattle feedlot-derived particulate matter (PM) is a major source of chemical and biological contaminants in surrounding air, water, soil, and sediment compartments in the Southern Great Plains (SGP) of North America. However, human and environmental risk assessment of feedlots are hindered due to a lack of air monitoring, and the spatial extent of downwind transport and deposition of PM and PM-bound agrochemicals is unclear. Therefore, to resolve present knowledge gaps, 1) USEPA’s CALPUFF dispersion model was used to validate inhalable PM (PM10 and PM2.5) emissions factors and model atmospheric transport from five feedlots, 2) total suspended particulates (TSP) were collected <1 - >12 km downwind of three feedlots to quantify seasonal agrochemical occurrence and cumulative human health risk, and 3) wet sediment was collected from playa wetlands in varying proximity to feedlots to assess seasonal agrochemical occurrence, source apportionment, and ecological risk to two benthic invertebrates (Hyallela azteca and Chironomus spp). CALPUFF-modeled emissions factors and PM concentrations from feedlots were greater overall in warmer months vs colder months, and peak diurnal emissions were frequently observed in the evening to early morning hours. National Ambient Air Quality Standards (NAAQS) for inhalable PM were exceeded at four of five feedlots over the duration of the modeling period, and modeled atmospheric transport of PM10 and PM2.5 posed a human health risk to surrounding communities within a 5-km discrete receptor extent. Pyrethroids and macrocyclic lactones (MLs) were frequently detected in downwind TSP (pyrethroids = 96.2; MLs = 98.1%) from May-August 2022, and downwind distance-decay of TSP indicated inhalable PM concentrations at levels that would significantly impact residents >12 km downwind during diurnal peak periods. Moreover, screening-level cumulative pyrethroid exposure estimates for agricultural communities in the SGP indicate elevated health risk for children 1-2 years of age. Of 21 agrochemicals analyzed in playa wetland sediment (n = 33), pyrethroid occurrence was considerable (75.8% of basins), and overall pyrethroid concentrations were significantly correlated with feedlot proximity (R2 = 0.178, p = 0.007). Overall organic carbon-normalized pyrethroid concentrations indicated acute high risk to benthic invertebrates in >75% of cases. Research results indicate significant impacts to surrounding human and ecological communities in the SGP, and a present lack of regulatory air monitoring at feedlot facilities places an undue burden on low-income, rural communities to demonstrate impacts to human health and public welfare.

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