Assessment of Bioaerosol Transport at a Large Dairy Operation

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 Laboratory
Kimberly, Idaho 83341
robert.dungan@ars.usda.gov

What are Bioaerosols?

• 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 µm
Bioaerosols

Bioaerosol Health Concerns
• Bioaerosols < 5 µm 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 µm 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 Known to Travel
Great Distances
Foot-and-Mouth disease
(FMD) transmission from
Brittany to Isle of Wight
across the English
Channel (1981)

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

Formation of Bioaerosols
• Animal movement
• Lot harrowing
• Feed preparation
• Land spreading of
manure solids and
wastewater
• Compost turning

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

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 protected
Clumped: 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

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

Wetted-Wall CycloneWetted-Wall CycloneImpingerImpinger
Impact SamplerImpact SamplerFilter SamplerFilter Sampler
Techniques Used to Capture Bioaerosols

Airborne Bacteria
CFUm-3
ofAir
Indicators of fecal
pollution generally
not detected (i.e.
total coliforms, E.
coli, and coliphage)

CFUm-3
ofAir
Diurnal Effects: Airborne Bacteria

Airborne Filamentous Fungi
CFUm-3
ofAir

CFUm-3
ofAir
Diurnal Effects: Airborne Fungi

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

Average Inhalable Endotoxin (< 100 µm)
EUm-3
ofAir

Diurnal Effect: Airborne Endotoxin

Factors Affecting Airborne
Endotoxin Concentrations
Lot
harrowing
event
Wind increased from
1.9 to 4.5 m s-1
Intermittent
cow activity
EUm-3
ofAir
Hour Hour

Predicted Ground-Level
Endotoxin Concentrations
EUm-3
ofAir
Downwind (m)

EUm-3
ofAir
WindN
Downwind (m)
Empirical Endotoxin Data at an
Open-Lot Dairy

Comparison of Endotoxin Levels
EU m-3
of Air

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

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

Acinetobacter Escherichia Planococcus
Arthrobacter Georgenia Pseudomonas
Bacteroides Halomonas Ralstonia
Bradyrhizobium Hymenobacter Rhizobium
Caulobacter Jeotgalicoccus Skermanella
Cellulomonas Marinobacter Sphingomonas
Chryseobacterium Methylobacterium Sphingopyxis
Clostridium Novosphingobium Staphylococcus
Corynebacterium 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

Evaporation/
Aerosolization Dispersion Inhalation
Risk of
infection
Deposition and
biological decay
Produce and fomites
Ingestion
Small droplets
(< 150 µm)
Large droplets (>
150 µm)
Deposition
Conceptual Model of Human Infection
from Land Application of Wastewater

Campylobacter jejuni Clostridium perfringens E. coli (EHEC)
Leptospira spp. Listeria monocytogenes Mycobacterium
avium
Salmonella enterica Yersinia
pseudotuberculosis
Cryptosporidium
/Giardia spp.
Pathogens in Dairy Wastewaters

Effect of Pressure and Spray Plate on
Microorganisms During Sprinkler Irrigation

Evaluation of Center Pivot Wind
Drift and Evaporation Loss

Capturing Aerosols, Drift, and Droplets

Wind Drift and Evaporation Results

Wind speed (m sec
-1
)
0 1 2 3 4 5
Percentappliedwateraerosolized
0.0
0.5
1.0
1.5
2.0
2.5
y = 1.3715x - 3.0323
R
2
= 0.77
Wind speed (m sec-1
)
0 1 2 3 4 5
Percentappliedwaterasdrift
0.1
0.2
0.3
0.4
0.5
0.6
0.7
y = 0.2535x - 0.3052
R
2
= 0.56
Percent of Applied Water Aerosolized or
Measured as Drift as Affected by Wind Speed

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

Thank you

Assessment of Bioaerosol Transport at a Large Dairy Operation

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Assessment of Bioaerosol Transport at a Large Dairy Operation