Quantitative Microbial Risk Assessment for Spray Irrigation of Dairy Manure Based on an Empirical Fate and Transport Model

• Published in: Environmental health perspectives 2017-08, Vol.125 (8), p.087009-087009
• Main Authors: Burch, Tucker R, Spencer, Susan K, Stokdyk, Joel P, Kieke, Jr, Burney A, Larson, Rebecca A, Firnstahl, Aaron D, Rule, Ana M, Borchardt, Mark A
• Format: Article
• Language: English
• Subjects: Agricultural Irrigation - methods; Agricultural production; Agriculture; Animal manures; Animal wastes; Campylobacter; Cattle; Computer simulation; Dairying; Distribution; E coli; Economies of scale; Environmental protection; Epidemics; Escherichia coli; Estimates; Exposure; Farms; Fecal coliforms; Food; Health aspects; Health risk assessment; Health risks; Irradiation; Irrigation; Livestock; Manure - microbiology; Manures; Medical research; Methods; Microorganisms; Models, Theoretical; Pathogenic microorganisms; Pathogens; R&D; Radiation; Relative humidity; Research & development; Risk Assessment; Risk factors (Health); Risk reduction; Salmonella; Spray irrigation; Sprinkler irrigation; Water quality; Weather; Wind speed; Zoonoses
• ISSN: 0091-6765; 1552-9924
• DOI: 10.1289/EHP283

Spray irrigation for land-applying livestock manure is increasing in the United States as farms become larger and economies of scale make manure irrigation affordable. Human health risks from exposure to zoonotic pathogens aerosolized during manure irrigation are not well understood. We aimed to ) estimate human health risks due to aerosolized zoonotic pathogens downwind of spray-irrigated dairy manure; and ) determine which factors (e.g., distance, weather conditions) have the greatest influence on risk estimates. We sampled downwind air concentrations of manure-borne fecal indicators and zoonotic pathogens during 21 full-scale dairy manure irrigation events at three farms. We fit these data to hierarchical empirical models and used model outputs in a quantitative microbial risk assessment (QMRA) to estimate risk [probability of acute gastrointestinal illness (AGI)] for individuals exposed to spray-irrigated dairy manure containing , enterohemorrhagic (EHEC), or spp. Median risk estimates from Monte Carlo simulations ranged from 10 to 10 and decreased with distance from the source. Risk estimates for or EHEC-related AGI were most sensitive to the assumed level of pathogen prevalence in dairy manure, while risk estimates for were not sensitive to any single variable. Airborne microbe concentrations were negatively associated with distance and positively associated with wind speed, both of which were retained in models as a significant predictor more often than relative humidity, solar irradiation, or temperature. Our model-based estimates suggest that reducing pathogen prevalence and concentration in source manure would reduce the risk of AGI from exposure to manure irrigation, and that increasing the distance from irrigated manure (i.e., setbacks) and limiting irrigation to times of low wind speed may also reduce risk. https://doi.org/10.1289/EHP283.