Michael A. Jahne

Emission and Dispersion of Bioaerosols from Dairy Manure Application Sites: Human Health Risk Assessment

In this study, we report the human health risk of gastrointestinal infection associated with inhalation exposure to airborne zoonotic pathogens emitted following application of dairy cattle manure to land. Inverse dispersion modeling with the USEPAs AERMOD dispersion model was used to determine bioaerosol emission rates based on edge-of-field bioaerosol and source material samples analyzed by real-time quantitative polymerase chain reaction (qPCR). Bioaerosol emissions and transport simulated with AERMOD, previously reported viable manure pathogen contents, relevant exposure pathways, and pathogen-specific dose-response relationships were then used to estimate potential downwind risks with a quantitative microbial risk assessment (QMRA) approach. Median 8-h infection risks decreased exponentially with distance from a median of 1:2700 at edge-of-field to 1:13 000 at 100 m and 1:200 000 at 1000 m; peak risks were considerably greater (1:33, 1:170, and 1:2500, respectively). These results indicate that bioaerosols emitted from manure application sites following manure application may present significant public health risks to downwind receptors. Manure management practices should consider improved controls for bioaerosols in order to reduce the risk of disease transmission.

Real-time investigation of antibiotics-induced oxidative stress and superoxide release in bacteria using an electrochemical biosensor

The involvement of oxidative stress in the mechanism of antibiotics-meditated cell death is unclear and subject to debate. The kinetic profile and a quantitative relationship between the release of reactive oxygen species (ROS), bacteria and antibiotic type remain elusive. Here we report direct measurements and analytical quantification of the release of superoxide radicals (O2(·-)), a major contributor to ROS, in antibiotics-treated bacterial cultures using a cytochrome c electrochemical biosensor. The specificity of electrochemical measurements was established by the addition of superoxide dismutase (SOD) which decreased the O2(·-) signal. Measurements using a general ROS-specific fluorescence dye and colony forming units (CFU) assays were performed side-by-side to determine the total ROS and establish the relationship between ROS and the degree of lethality. Exposure of Escherichia coli and Listeria monocytogenes cultures to antibiotics increased the release of O2(·-) radicals in a dose-dependent manner, suggesting that the transmembrane generation of ROS may occur as part of the antibiotic action. The study provides a quantitative methodology and fundamental knowledge to further explore the role of oxidative stress in antibiotics-meditated bacterial death and to assess physiological changes associated with the complex metabolic events related to oxidative stress and bacterial resistance.

Bioaerosol Deposition to Food Crops near Manure Application: Quantitative Microbial Risk Assessment

Production of both livestock and food crops are central priorities of agriculture; however, food safety concerns arise where these practices intersect. In this study, we investigated the public health risks associated with potential bioaerosol deposition to crops grown in the vicinity of manure application sites. A field sampling campaign at dairy manure application sites supported the emission, transport, and deposition modeling of bioaerosols emitted from these lands following application activities. Results were coupled with a quantitative microbial risk assessment model to estimate the infection risk due to consumption of leafy green vegetable crops grown at various distances downwind from the application area. Inactivation of pathogens ( spp., spp., and O157:H7) on both the manure-amended field and on crops was considered to determine the maximum loading of pathogens to plants with time following application. Overall median one-time infection risks at the time of maximum loading decreased from 1:1300 at 0 m directly downwind from the field to 1:6700 at 100 m and 1:92,000 at 1000 m; peak risks (95th percentiles) were considerably greater (1:18, 1:89, and 1:1200, respectively). Median risk was below 1:10,000 at >160 m downwind. As such, it is recommended that a 160-m setback distance is provided between manure application and nearby leafy green crop production. Additional distance or delay before harvest will provide further protection of public health.

Case Study: Occasional excessive ammonia emissions following dairy manure application to land: causes, impacts, and management recommendations

Abstract. Ammonia is being monitored and modeled following land application of dairy manure to determine the impacts of application method on its emission, transport, and deposition. Ammonia emission flux from manure applied fields and downwind concentrations are measured following conventional splash plate spreading, direct injection, and drag-hose application of liquid dairy manure. Conventional broadcast spreading has produced the greatest nitrogen emissions from both the field and lab soil experiments; exposure concentrations in excess of OSHA’s Permissible Exposure Limit (PEL) of 35 mg/m 3 have been observed. On two instances, ammonia emissions flux exceeded 111 mg/m 2 /hr, the maximum emissions rate that our instrument could monitor. This equated to 3.6 times the average ammonia emissions flux of the remaining sampling events. Atmospheric ammonia concentrations on those dates reached 56 mg/m 3 , far exceeding OSHA’s PEL. Here, we report the causes of these excessive ammonia-N fluxes, potential impacts, and management recommendations to avoid high ammonia emissions events and preserve valuable nitrogen fertilizer.

Impacts of manure spreading on downwind air quality: particles, ammonia, and bioaerosols

Ammonia, particulate matter, and bioaerosols are being monitored at edge-of-field following land application of dairy manure to determine the impacts of application technique and anaerobic digestion on emission, transport, and deposition of these pollutants. Our goal is to produce data and improve models useful for the development of science-based emission reduction targets to improve air quality and protect human and environmental health. Here, we present data from our first sampling season of the three year study. Ammonia emission flux from manure-amended soils and downwind deposition were measured following conventional splash-plate spreading, direct injection, and drag-hose application of manure at a dairy CAFO in northern New York. Ambient particle concentrations were measured in four size bins during each event. Size-segregated samples were collected for both microbial cultivation and molecular analysis using real-time quantitative polymerase chain reaction (qPCR) to measure populations of total bacteria, Enterococcus spp., and fecal Bacteroidales. Results of this work will serve as the basis for future fate and transport modeling, which will lead to an improved understanding of air quality implications of manure application for farm workers, nearby residents, and local environmental systems.

Bacterial Characterization, Deposition, and Emission Factors for Particulate Matter Generated During the Land Application of Dairy Manure in Northern New York

Although land application of livestock manure remains a standard agricultural practice, it poses a risk to both human and environmental health. Among other concerns, manure is host to a number of microbial pathogens that have been shown to persist in soils and runoff to local waterways following field application. A significant body of research exists regarding the risks of particulate matter and bacteria in the air of livestock confinement houses and emitted during land application of treated human waste biosolids. However, little has been done to assess air quality impacts during land application of untreated livestock manures. In this study, we characterize emission and deposition rates of bioaerosols for broadcast (conventional splash-plate) spreading of manure at a dairy CAFO in northern New York. Horizontal and vertical arrays of sampling equipment at edge-of-field were used to collect size-segregated aerosol and deposition samples, which were analyzed using real-time quantitative polymerase chain reaction (qPCR) to measure populations of total bacteria, Enterococcus spp., and fecal Bacteroidales. Emission factors were calculated through correlation with PM10 flux measurements and deposition velocities established by direct flux measurement. These results will serve as the basis for future fate and transport modeling, which will lead to an improved understanding of the air quality implications of manure application for farm workers, nearby residents, and local environmental systems.