assessment of bioaerosol transport at a large dairy operation
DESCRIPTION
Proceedings available at: http://www.extension.org/67599 In an effort to assess the off-site transport of bioaerosols, airborne bacteria, fungi, and endotoxin were collected at a 10,000 cow dairy operation. Compared to background locations, the general trend was that bioaerosol concentrations were higher immediately downwind, then decreased with distance from the animal housing. While bioaerosol concentrations did not follow a seasonal trend, they did significantly correlate with meteorological factors such as temperature and solar radiation. Bioaerosol concentrations were also found to be greatest at night, which can be attributed to changes in animal activity and wind speed and reduced exposure of the microorganisms to UV radiation. An analysis of clones generated from air samples collected downwind from the animal housing and pivots spraying dairy wastewater revealed that none of sequence matches were affiliated with bacteria known to be pathogenic to otherwise healthy humans. Results from ongoing research to better understand bioaerosol formation and drift losses during spray irrigation events of dairy wastewater will also be discussed.TRANSCRIPT
United States Department of Agriculture
Agricultural Research Service
Assessment of Bioaerosol Transport at Large Dairy Operations
Drs. Robert S. Dungan, April Leytem, and David Bjorneberg
Northwest Irrigation & Soils Research LaboratoryKimberly, Idaho 83341
United States Department of Agriculture
Agricultural Research Service
What are Bioaerosols?
United States Department of Agriculture
Agricultural Research Service
• Viable and nonviable airborne biological particles and their fragments/byproducts
• Bacteria, virus, fungal spores, pollen, mycotoxin, endotoxin
• Mixture of droplets and dry particles
• Aerodynamic diameters ranging from 0.5 to 100 m
Bioaerosols
United States Department of Agriculture
Agricultural Research Service
Bioaerosol Health Concerns
• Bioaerosols < 5 m in dia. present the most concern since they are readily transported into the lungs
• Microbial component of inhaled agricultural dusts contributes significantly to pulmonary diseases
• Allergenic, toxic, and inflammatory responses are caused not only by exposure to viable but also nonviable microorganisms and their fragments (e.g. endotoxin)
• Bioaerosols < 5 m in dia. present the most concern since they are readily transported into the lungs
• Microbial component of inhaled agricultural dusts contributes significantly to pulmonary diseases
• Allergenic, toxic, and inflammatory responses are caused not only by exposure to viable but also nonviable microorganisms and their fragments (e.g. endotoxin)
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Agricultural Research Service
Bioaerosols Known to Travel Great Distances
Foot-and-Mouth disease (FMD) transmission from Brittany to Isle of Wight across the English Channel (1981)
United States Department of Agriculture
Agricultural Research Service
Dairies as a Source of Bioaerosols
• High stocking density and large quantities of manure (55 kg/day)
• Increase in the microbial load within the production environment
• Livestock harbor a variety of zoonotic pathogens, which are excreted with feces
• Bioaerosols a potential health risk to livestock, farm workers, and those offsite
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Agricultural Research Service
Formation of Bioaerosols
• Animal movement• Lot harrowing • Feed preparation• Land spreading of
manure solids and wastewater
• Compost turning
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Agricultural Research Service
Viability of Airborne Microorganisms
• Temperature
• Solar radiation
• Humidity
• Temperature
• Solar radiation
• Humidity
In general, viability decreases with increases in solar radiation and temperature and decreases in relative humidity
In general, viability decreases with increases in solar radiation and temperature and decreases in relative humidity
United States Department of Agriculture
Agricultural Research Service
Role of Solids-Association in Microbial Survival
Sobsey (1984)
Embedded: most protected
Embedded: most protected
Dispersed: least protected
Dispersed: least protected
Adsorbed: partially
protected
Adsorbed: partially
protected
Clumped: interior microbes protectedClumped: interior
microbes protected
• Microbes can be on or in larger particles or they can be aggregated
• Association of microbes with solids or particles and microbial aggregation is generally protective
• Microbes are shielded from environmental agents by association with solids
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Agricultural Research Service
10,000 Cow Open-Freestall Dairy
• Aerosol samples were collected in the morning, afternoon, and night
• Spring, summer, and fall• Quantified heterotrophic
bacteria, total coliforms , E. coli, coliphage, fungi, and endotoxin
• Bacterial DNA was used to create a clone library of 16S rRNA genes
N
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Agricultural Research Service
Wetted-Wall CycloneWetted-Wall CycloneImpingerImpinger
Impact Sampler Impact Sampler Filter SamplerFilter Sampler
Techniques Used to Capture Bioaerosols
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Agricultural Research Service
Airborne BacteriaCF
U m
-3 o
f Air
Indicators of fecal pollution generally not detected (i.e. total coliforms, E. coli, and coliphage)
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Agricultural Research Service
CFU
m-3
of A
ir
Diurnal Effects: Airborne Bacteria
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Agricultural Research Service
Airborne Filamentous Fungi
CFU
m-3
of A
ir
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Agricultural Research Service
CFU
m-3
of A
ir
Diurnal Effects: Airborne Fungi
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Agricultural Research Service
Facts About Airborne Endotoxin
• Ubiquitous in the environment• Inhalation is the main route for
exposure• Cough, airway irritation, and
decreased pulmonary function• At high exposure levels, fever
and influenza-like symptoms may develop
• Some studies suggest a lower risk for asthma and lung cancer
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Agricultural Research Service
Average Inhalable Endotoxin (< 100 m)
EU m
-3 o
f Air
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Agricultural Research Service
Diurnal Effect: Airborne Endotoxin
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Agricultural Research Service
Factors Affecting Airborne Endotoxin Concentrations
Lot harrowing event
Wind increased from 1.9 to 4.5 m s-1
Intermittent cow activityEU
m-3
of A
ir
Hour Hour
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Agricultural Research Service
Predicted Ground-Level Endotoxin Concentrations
EU m
-3 o
f Air
Downwind (m)
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Agricultural Research Service
EU m
-3 o
f Air
WindN
Downwind (m)
Empirical Endotoxin Data at an Open-Lot Dairy
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Agricultural Research Service
Comparison of Endotoxin Levels
EU m-3 of Air
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Agricultural Research Service
Item Air Temp Relative Humidity
Solar Radiation
Wind speed
Endotoxin 0.318*** -0.150 -0.178* 0.074
Bacteria 0.149* -0.166* -0.137* 0.165*
Fungi 0.138* 0.117 -0.117 -0.246***
Pearson Correlation Coefficients (r) Between Bioaerosol and Meteorological Factors
*, **, *** Indicate significant differences at 0.05, 0.01, and 0.001 probability levels, respectively
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Agricultural Research Service
Phylum Background Dairy barns and lots
Pivots spraying dairy wastewater
Actinobacteria 3 (2%) 2 (4%)
Bacteroidetes 2 (7%) 11 (8%) 4 (8%)
Firmicutes 3 (10%) 13 (9%) 5 (10%)
Proteobacteria 24 (83%) 111 (78%) 33 (69%)
Unclassified 5 (3%) 4 (8%)
Number (and Percentage) of Unique Clone Sequences Affiliated With the Bacterial Phyla
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Acinetobacter Escherichia PlanococcusArthrobacter Georgenia Pseudomonas Bacteroides Halomonas RalstoniaBradyrhizobium Hymenobacter Rhizobium Caulobacter Jeotgalicoccus SkermanellaCellulomonas Marinobacter Sphingomonas Chryseobacterium Methylobacterium Sphingopyxis Clostridium Novosphingobium StaphylococcusCorynebacterium Paracoccus Variovorax
Common Bacterial Genera in the Dairy Aerosol Samples
• Only 3% of the sequences were homologous with bacteria from cow milk, rumen, and fecal samples
• No sequences were affiliated with bacteria known to be pathogenic to non-immunocompromised individuals
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Agricultural Research Service
Evaporation/ Aerosolization Dispersion Inhalation
Risk of infection
Deposition and biological decay
Produce and fomites
Ingestion
Small droplets (< 150 m)
Large droplets (> 150 m)
Deposition
Conceptual Model of Human Infection from Land Application of Wastewater
United States Department of Agriculture
Agricultural Research Service
Campylobacter jejuni Clostridium perfringens E. coli (EHEC)
Leptospira spp. Listeria monocytogenes Mycobacterium avium
Salmonella enterica Yersinia pseudotuberculosis
Cryptosporidium/Giardia spp.
Pathogens in Dairy Wastewaters
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Agricultural Research Service
Effect of Pressure and Spray Plate on Microorganisms During Sprinkler Irrigation
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Agricultural Research Service
Evaluation of Center Pivot Wind Drift and Evaporation Loss
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Agricultural Research Service
Capturing Aerosols, Drift, and Droplets
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Agricultural Research Service
Wind Drift and Evaporation Results
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Agricultural Research Service
Wind speed (m sec-1)
0 1 2 3 4 5
Pe
rce
nt a
pp
lied
wa
ter
ae
roso
lize
d
0.0
0.5
1.0
1.5
2.0
2.5
y = 1.3715x - 3.0323R2 = 0.77
Wind speed (m sec-1)
0 1 2 3 4 5
Pe
rcent a
pp
lied w
ater a
s drift
0.1
0.2
0.3
0.4
0.5
0.6
0.7
y = 0.2535x - 0.3052R2 = 0.56
Percent of Applied Water Aerosolized or Measured as Drift as Affected by Wind Speed
United States Department of Agriculture
Agricultural Research Service
Summary and Concluding Remarks
• Dairies are a source of elevated bioaerosol concentrations, which decrease with increasing distance
• The level of bioaerosol did not follow a seasonal trend, but did correlate with some meteorological factors
• Clone sequences were not affiliated with human pathogens
• Risk of bioaerosol exposure should be minimal at extended downwind distances
United States Department of Agriculture
Agricultural Research Service
Thank you