Browsing by Author "Reynolds, Stephen J., advisor"
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Item Open Access A comparative analysis between the rFC and LAL endotoxin assays for agricultural air samples(Colorado State University. Libraries, 2016) Krause, Laura Ann, author; Reynolds, Stephen J., advisor; Schaeffer, Joshua W., committee member; Ellis, Robert P., committee memberAgricultural workers experience increased exposure to inhalable dust and endotoxins, which make up the outer membrane of Gram-negative bacteria species. Endotoxin has specifically been linked to an increased degree of pro-inflammatory symptoms from inhaled dust, leading to a variety of lung diseases. Because there is no standardized method of collection or analysis of endotoxin, there are paramount gaps in the knowledge of how best to collect and analyze samples. The aims of this study were to: (1) assess the recovery from PVC filters spiked with known endotoxin concentrations; and (2) compare two different biological endotoxin assay kits: Lonza rFC and Associates of Cape Cod Pyrochrome Chromogenic, in order to detect any significant variation in measured endotoxin concentrations and potentially establish a conversion factor for interstudy comparison purposes. The LAL assay uses a component found in the blood of horseshoe crabs in order to detect and quantify endotoxin concentrations. This process poses some concern with variability, as the reactivity of lysate with endotoxin can vary greatly between individual horseshoe crabs. The newer rFC assay offers an additional option for endotoxin analysis that does not require the use of horseshoe crabs. Because all of the materials are produced in a laboratory, the consistency between kits is much higher. In Aim 1, PVC filters in replicates of five were liquid-spiked with 5 levels of known amounts of endotoxin. To simulate effects of sampling and handling, each filter was then desiccated for 24 hours and loaded into SKC Button Aerosol Samplers where air was pulled through them for 4 hours at a flowrate of 4 L/min to mimic field sampling conditions. Samples were then frozen at -80ºC, thawed, and extracted. Each sample was analyzed for endotoxins using the rFC assay. For Aim 2, a combination of personal, area, and field blanks were collected from two Colorado dairy farms from 2013-2014 in conjunction with a larger study for a total sample size of n=31. Samples were desiccated for 24 hours, frozen at -80ºC, thawed, and extracted. Each sample was then analyzed using the rFC and LAL assay and the results were compared. Using the rFC assay, measurements for endotoxin concentrations were on average several magnitudes lower than the anticipated concentration. Spike recoveries ranged from 1-8%. It is likely that the hydrophobic properties of the PVC filters did not allow complete absorption of the liquid spikes, but rather evaporated into the air. For aim 2, there was no statistical difference found between the rFC and LAL assay for the total sample set (p-value 0.7146) using an alpha=0.10. There was also no statistical difference between assay types for the personal sample subset (p-value 0.3788). However, there was a statistically significant difference for the area sample subset (p-value 0.0698) and the lab and field blank sample subset (p-value 0.06638). Due to the small sample size, the power had to be adjusted to accommodate an alpha value of 0.10. The correlation between observations for all samples was found to be reasonably high with an r value of 0.867. The R2 coefficient value was found to be 0.7524. This indicates that 75.24% of the variability in LAL assay data can be explained by rFC assay data. The rFC assay serial dilution of standards gives a much more broad detection range of 0.005-5.0 EU/ml. The LAL standards only cover a fraction of this range, going from 0.005-0.04 EU/ml, 0.02-0.16 EU/ml, and 0.16-1.28 EU/ml. This dramatically decreases the chances of correctly identifying the dilution factor on the first attempt, and can create additional costs to use extra kits for re-analysis. The rFC assay can also be a considerably more cost effective option when purchasing in bulk of 20-30 kits at a time; however, when purchased individually, the LAL assay is less expensive. Overall, the development of the rFC assay greatly reduces the amount of horseshoe crabs harvested and bled for collection, reduces the costs of formulating the lysate enzyme, and most significantly, reduces the inconsistency in endotoxin measurement results.Item Open Access Air toxic assessment for short-term ambient air pilot study at private house in Battlement Mesa near oil and gas drilling site(Colorado State University. Libraries, 2011) Alhaji, Hussain, author; Reynolds, Stephen J., advisor; Brazile, William Joseph, committee member; Kreidenweis, Sonia M., committee memberThis pilot study evaluated the ambient air concentrations in Battlement Mesa, Colorado at private house near a well pad, for the four-day period of February 7 through February 10 of 2011. The natural gas site was operating in the production phase of oil and gas development process, and there were 12 wells commercial line. The overlying purpose of the study was to provide preliminary evaluation of air quality characteristics within Battlement Mesa with particular attention to Speciated Non-Methane Organic Compounds/Volatile Organic Compounds (SNMOC/VOCs), fine particulate matter (PM2.5) and total volatile organic compounds (TVOC's). SNMOCs including benzene, toluene, ethylbenezene, and xylene (BTEX) compounds were collected and analyzed using a modified EPA Organic Compendium Method TO-12 over a 22-hour period using Summa-polished stainless steel canisters. PM2.5 levels were measured using a directing reading photometer, a Personal Data RAM (pDR-1200) for 24-hour sampling period. Total VOCs, were measured in real-time using a Rae Systems PPB Rae 3000 photo ionization detector (PID). To measure the meteorological data, a portable weather station was deployed at the fire station site (FR) during the sampling period (about half mile from the sampling location). Sampling was performed at two locations around the private house, and background samples were collected at the FR for each parameter. The large percentage of detection (high prevalence i.e. ~95%) in samples from all sites appears to indicate that local VOCs sources do have impacts on air pollution levels. Compounds that were detected in the highest concentrations were light alkanes (i.e. ethane, propane) and the BTEX group (benzene, toluene, ethylbenzene and xylenes). The BTEX group, benzene in particular, recorded a potential health risk compared to the Risk Based Concentration (RBC) developed by the Environmental Protection Agency (EPA). In general, the SNMOCs/VOCs levels detected were low for all samples. TVOCs levels were also low and are consistent with the BTEX group where the background site recoded higher levels than the sampling sites (Upstream "UP" and Downstream "DN" sites). No exceedances of Federal National Ambient Air Quality Standards were recorded for PM2.5. In addition, PM2.5 concentrations were generally highest in the UP site which is close to the well pad. Comparisons of PM2.5 data to data from other studies in Garfield County show that PM2.5 concentrations in Battlement Mesa (oil and gas development area) are similar to or higher than the Rifle area (urban area) Meteorological monitoring was performed on a continuous basis with one-hour averages being generated. Wind speed and precipitation (snow) are the most pronounced meteorological parameters that are correlated with VOCs and PM2.5 levels. Overall for the study, pollutant levels were found to be generally very low as compared to the standards and suggested guidelines. In some locations, it is likely that more elevated pollutant levels are the result of local or individual sources. BTEX emissions sources should be evaluated more thoroughly and benzene in particular since elevated levels were observed. Given that benzene recorded a potential health hazard in the area (exceeded lower level for cancer risk), it is recommended that a comprehensive air study that measures VOCs at different seasons and at other well-development processes be conducted. The background site (FR) is affected by several emission sources. Therefore, it is recommended to relocate the background site to have a better representative background. A direct reading photometer method using the Personal Data RAM (pDR1200) is not the best method to collect the particulates during the winter season due to instrument related temperature bias. Therefore, an alternative method to measure the particulate matter is advised.Item Open Access Analyses and exposure assessment of bacterial endotoxin in agricultural environments(Colorado State University. Libraries, 2008) Saito, Rena, author; Reynolds, Stephen J., advisorEndotoxins, or lipopolysaccharides (LPS), found in organic dust are a component of the cell membrane of Gram-negative bacteria that play an important role in respiratory disease. However, accurate endotoxin measurements are difficult in agricultural environments since agricultural dusts contain a complex mixture of biological and chemical agents. This dissertation research was designed to improve the understanding of the variability in endotoxin measurements in agricultural environments. The first study determined patterns of 3-OHFA distribution in dusts from dairy farms, cattle feedlots, grain elevators, and farms, and evaluated correlations between the GC/EI-MS and the rFC bioassay results. Patterns of 3-OHFA distribution varied by dust type; livestock dusts contained approximately two times higher concentrations of 3-OHFAs than grain dusts. Pearson correlations and multiple regressions showed higher correlations between GC/EI-MS and rFC results for livestock dusts than for grain dusts. Odd-chain length 3-OHFAs were found to correlate with rFC responses, as well as with even-chain length 3-OHFAs. The second study evaluated traditional LAL and novel rFC assay responses to endotoxins in chicken, dairy, horse, swine, and turkey dusts, and investigated potential interference with assays using GC/EI-MS. Strong positive correlations existed between LAL and rFC results, but responses to assays varied by dust type. LAL overestimated/rFC underestimated endotoxin exposures in chicken and horse dusts, and LAL underestimated/rFC overestimated endotoxin concentrations in dairy, swine, and turkey dusts. The variability in assay responses might be explained by differences in bacterial composition and other dust components; the rFC assay may react positively with Actinobacteria. The third study characterized agricultural tasks and evaluated determinants of personal dust and endotoxin exposures in dairy farms, cattle feedlots, grain elevators, and farms. Dust and endotoxin exposures differed by agricultural environment and by task and combinations of tasks varied by environment. Regression analysis indicated that hours at running legs in grain elevators was the major determinant of dust. Hours at running legs in grain elevator and hours at feeding livestock in cattle feedlots were two major determinants in endotoxin measurements. This dissertation addressed the need for understanding differences in agricultural environments for endotoxin exposure assessment.Item Open Access Baseline evaluation of indoor air quality from Nicaraguan households using traditional cook stoves(Colorado State University. Libraries, 2010) Bazemore, Heather, author; Reynolds, Stephen J., advisor; Peel, Jennifer L., advisor; Kreidenweis, Sonia M., committee memberIndoor cook stoves are still used as a primary energy source across the world in many developing countries. Inefficient stoves cause incomplete combustion of biomass fuel, resulting in an unhealthy increase of indoor air pollutants, including carbon monoxide (CO) and particle matter (PM). Use of these stoves is a global problem that must be addressed to help reduce indoor air pollutant exposures and combustion emissions. Most studies assessing traditional cook stoves are limited; the extended length and thorough exposure assessment of this study make it unique, providing better data for evaluation. This part of the study will assess the baseline exposure data from a longitudinal study of 123 Nicaraguan households collected over the summer of 2008. Fine particulate matter (PM2.5) was assessed continuously via 48-hour indoor monitoring using the UCB Particle Monitor. Indoor and personal carbon monoxide levels were assessed continuously via 48-hour indoor and personal monitoring using the lightweight, portable, data-logging Drager Pac 7000. PM2.5 and carbon monoxide indoor sampling devices were collocated inside the kitchen at a height representative of breathing zones. The personal carbon monoxide device was worn by the participant during the day and placed by her bedside overnight. Regression exposure models were developed using variables from the kitchen that can predict ventilation, including amount of eave space, kitchen volume, number of windows, number of doors, number of walls, and primary type of wall material. Cooking practices and activities were also considered in the models including exposure to environmental tobacco smoke, hours spent cooking per day, hours fire burns per day, and hours spent in the room with the fire burning per day. At the end of the summer baseline collection, improved cook stoves were installed in each participating household. High concentrations of indoor air pollution were recorded in households using traditional cook stoves. For indoor carbon monoxide, mean concentrations were 146 ppm (1-hour max), 67 ppm (8-hour max), and 26 ppm (48-hour). For personal CO, mean concentrations were 32 ppm (1-hour max), 8 ppm (8-hour max), and 2 ppm (48-hour). For indoor PM2.5, mean concentrations were 11,272 μg/m3 (1-hour max), 3655 μg/m3 (8-hour max), and 1364 μg/m3 (48-hour). In exposure assessment models, kitchen volume and exposure to environmental tobacco smoke were found to explain the most variation in indoor carbon monoxide levels. For personal carbon monoxide, number of doors and hours spent cooking per day influenced levels most. Amount of eave space and environmental tobacco smoke explained the most variation in indoor PM2.5 levels. Peaks in pollutant exposure were also evaluated in assessment models. However, all model results should be interpreted with caution. R-square values were very low for these models, meaning that the variables we collected data on did not explain much variation in pollutant concentrations. The data collected on exposure parameters did not explain much variation in indoor air quality. Further research is needed as to which housing factors and/or cooking practices affect pollutant levels most.Item Open Access Comparative analysis of bacterial and fungal communities in two dairy parlors through the use of pyrosequencing, riboprinting, culture techniques, and microscopic analysis(Colorado State University. Libraries, 2013) VanDyke-Gonnerman, Amanda L., author; Reynolds, Stephen J., advisor; Volckens, John, committee member; Ellis, Robert, committee memberThe purpose of this study was to compare three different analysis techniques used to characterize and identify bacteria and fungi. Pyrosequencing, culture techniques, and riboprinting were compared for all of the bacterial samples and pyrosequencing; culture techniques; and microscopic analysis was used to compare the fungal samples. SKC BioSamplers were used to take area samples inside two modern dairy parlors from May 2012-January 2013. Four sampling sessions were completed at each dairy parlor. Four biosamplers ran side-by-side (two at a time) for 60 minutes at 12.5 l/min in addition to a lab and a field blank. A novel resuscitation buffer was used to collect and aid recovery of stressed bacteria and fungi. Three types of media were used to select for bacteria and fungi: tryptic soy agar (TSA) with a 5% sodium chloride addition for Gram-positive bacteria; Eosin methylene blue (EMB) for Gram-negative bacteria, and malt extract agar (MEA) with a chloramphenicol addition for fungi. Based on colony morphology, the five most commonly encountered bacteria from both TSA and EMB agar were subcultured and identified through riboprinting. Pyrosequencing was performed directly on the biosampler collection media. The culturable bacterial concentrations and the pyrosequencing bacterial concentrations were within the same order of magnitude, which was unexpected. The culturable bacterial concentrations, with averages of 7500 CFU/m3 and 500 CFU/m3 for TSA and EMB plates respectively, were higher than the concentrations found in previous studies which could be a result of the novel resuscitation buffer that was used as a collection media. Greater microbiome diversity was found through pyrosequencing analysis than the riboprinting analysis. The pyrosequencing data found many genera that include species that are pathogenic, but more work must be done to confirm if pathogenic species were found during sampling at these two dairy parlors. The riboprinting samples were identified on the species and strain level and found Escherichia coli O157:H7 a known pathogen as well as Pseudomonas aeruginosa, an opportunistic pathogen. The culturable fungi concentrations and the pyrosequencing concentrations were within the same order of magnitude, which was also unexpected. The pyrosequencing data had greater diversity than the microscopic analysis for the first two sets of samples that were sent for pyrosequencing. The second set of fungal samples that were sent for pyrosequencing came back as non-detect samples despite the growth of fungi on the agar. From the pyrosequencing data, there were many genera found that have pathogenic species, but more research needs to be conducted to determine the presence of the pathogenic species. There were no pathogenic fungal species found through the microscopic analysis.Item Open Access Comparison of occupational and environmental exposures at Colorado dairies(Colorado State University. Libraries, 2008) Lester, Bradley Raymond, author; Reynolds, Stephen J., advisorOccupational contaminant levels and environmental emissions were compared at two Colorado dairies. Along with meteorological conditions, analytes measured included odor, hydrogen sulfide, ammonia, total and inhalable particulate and endotoxin, and bioaerosols including fungi, mesophilic bacteria, and gram-negative bacteria. Meteorologic conditions varied widely in temperature (range: -12.5 - 4 1.1°C), relative humidity (range: 0.6 - 92.3%) and wind speeds during sampling (range: 0.48 - 8.66 m/s). Geometric mean bioaerosol concentrations for the Anderson sampler and SKC Biosampler include: mesophilic bacteria, 1282 and 383 CFU/m3, gram-negative bacteria, 667 and 265 CFU/m 3, and fungi, 781 and 252 CFU/m3. The Anderson sampler collected significantly (p<0.001) higher bioaerosol concentrations for all three categories. Peak ammonia levels at the study and control dairies ranged from 2.0 - 142 and 2.0 - 23 ppm. Peak ammonia was significantly (p<0.05) higher at the study dairy. Mean hydrogen sulfide levels at the study and control dairies ranged from 4.0 - 394 and 4.0 - 890 ppb. Peak hydrogen sulfide levels at the study and control dairies ranged from 37 - 17,000 and 210 - 5,200 ppb. Mean peak hydrogen sulfide was significantly (p<0.05) higher at the control dairy. Odor measures ranged from 0-15 D/T at both dairies. Inhalable particulate at study and control dairy lagoons ranged from < LOD - 2.3 mg/m3. Inhalable endotoxin at study and control dairy lagoons ranged from 2.1 - 487.2 EU/m3. Total particulate at study and control dairy lagoons ranged from < LOD to 2.4 mg/m3. Total endotoxin at study and control lagoons ranged from 2.5 - 6587 EU/m3. Inhalable particulate for tasks at both dairies ranged from 0.06 - 8.0 mg/m3. Total particulate for tasks at both dairies ranged from 0.03 - 6.9 mg/m 3. Inhalable endotoxin for tasks at both dairies ranged from 2.0 - 11096 EU/m3. Total endotoxin for tasks at both dairies ranged from 5.9 - 6758 EU/m3. Supported by NIOSH Grant 5U500H008085.Item Open Access Comparison of the limulus amebocyte lysate (LAL) and recombinant factor C (rFC) endotoxin bioassays: characterization of aerosols and settled dust on a sheep farm(Colorado State University. Libraries, 2011) Sorrentino, Jennifer Virginia, author; Reynolds, Stephen J., advisor; Keefe, Thomas J., committee member; Goodridge, Lawrence D., committee memberThe goals of this study are: 1) To optimize an extraction protocol for bulk sheep dust analysis by rFC; 2) To compare the traditional chromogenic LAL to the newer fluorometric rFC assay; 3) To compare the effects of the two most widely used extraction media, pyrogen-free water (PFW) and pyrogen-free water with 0.05% Tween 20 (PFW-Tween 20), on the assay outcomes; and 4) To characterize endotoxin exposure in a sheep farm environment. Settled and airborne dust samples were collected from a sheep farm for analysis. Settled dust was analyzed with endpoint fluorogenic rFC and kinetic chromogenic LAL in two different laboratories. A total of 34 stationary airborne dust samples (32 matched) were collected with Institute of Occupational Medicine (IOM) inhalable dust samplers, using polyvinyl chloride (PVC) filters. Airborne samples were analyzed with endpoint fluorogenic rFC and endpoint chromogenic LAL in the same laboratory. The results of the bulk dust analysis showed a significant difference in polystyrene (PS) tubes and polypropylene (PP) tubes used for extraction indicating that PS tubes yielded higher endotoxin levels (t = 3.82, p = 0.000). No difference in endotoxin levels was found for centrifugation and spike recovery was closest to 100% for extraction with PFW. The results of the airborne dust study showed a strong positive correlation between the rFC and LAL assays with PFW-Tween 20 extraction. All samples extracted in PFW-Tween 20 had a higher endotoxin recovery compared with those extracted in PFW for both the rFC and LAL assays.Item Open Access Contribution of exposure and genetics to the development of beryllium sensitization and chronic beryllium disease(Colorado State University. Libraries, 2010) Van Dyke, Michael V., author; Reynolds, Stephen J., advisor; Martyny, John William, committee member; Keefe, Thomas J., committee member; Nelson, Tracy L., committee member; Sandfort, Delvin R., committee memberTo view the abstract, please see the full text of the document.Item Open Access Evaluation of bacterial sampling methods for use with the bacterial tag-encoded flexible (FLX) amplicon pyrosequencing (bTEFAP) technique(Colorado State University. Libraries, 2012) Robinson, Douglas L., author; Reynolds, Stephen J., advisor; Goodridge, Larry, committee member; Brazile, William, committee memberBackground: The need to enumerate airborne microorganisms during infectious disease outbreaks, indoor air quality evaluations, and agricultural health studies has identified limitations in culture-based or viable sampling and characterization of bioaerosols. Pyrosequencing promises to be a novel, molecular-based technology that is exceptionally sensitive, low-cost, and provides a reasonable turnaround in the identification, distribution and concentration of aerosolized microorganisms. However, bioaerosol sampling methods for use with pyrosequencing have not been thoroughly evaluated. The intent of this project was to investigate a standardized sampling protocol for use with bTEFAP that would ultimately provide occupational scientists a novel and effective tool in the quest to characterize bioaerosol exposure and its subsequent relationship to worker health. Methods: Four filter types (Millipore Durapore® Membrane Filter, SKC water-soluble gelatin filter, SKC PTFE, SKC PVC) were prescreened for low-background DNA content using Pyrosequencing. Studies comparing the performance of the SKC Polyvinylchloride (PVC) and SKC gelatin filters in IOM samplers to an impinger - the SKC biosampler - were conducted in a previously characterized bioaerosol chamber using a Collision nebulizer. The challenge organism was a spore former, Bacillus atrophaeus. Tag-encoded FLX amplicon pyrosequencing analyses utilized Roche 454 FLX instrument with DNA extraction, massively parallel bTEFAP and bacterial identification data analysis was performed at the Research and Testing Laboratory (Lubbock, TX). Results: From an initial filter analysis, both the SKC PVC and SKC gelatin filters were selected for use in this project based on low-background DNA content, ease of use and cost. The two filter types and the SKC biosampler were challenged against B. atrophaeus for 30 minute sampling times in a series of six trials. Post pyrosequencing of detectable samples, it was demonstrated that the biosampler performed less effectively when compared to the PVC (p=0.0002) and gelatin filter (p=0.0006) based on an alpha value of 0.05. No significant difference was demonstrated between the two filter types (p=0.8). Of the original n=66 samples analyzed through pyrosequencing, only n=15 were reported to have counts for the challenge organism. In comparison to the pyrosequencing data, the cultured count demonstrated a significant difference when compared to the filters and biosampler media (p=0.003) in countable spores. Conclusions: The results indicate that with the model used in this study, the biosampler performed significantly different when compared to two filter types, the SKC PVC and the SKC gelatin, when challenged with B. atrophaeus. In addition, the microbial results suggest that there is possible significant contamination in the pyrosequencing methods used and or in the handling methods prior to analysis. Method analysis needs to be completed before further studies are completed.Item Open Access Evaluation of Sabine’s Formula on the prediction and control of reverberant noise in a modern LEED Platinum certified research building(Colorado State University. Libraries, 2016) Quinn-Vawter, Christopher, author; Reynolds, Stephen J., advisor; Brazile, William J., committee member; Wilson, Bryan D., committee memberThe Powerhouse Energy Campus is a LEED Platinum certified research building located in Fort Collins, Colorado and is part of Colorado State University. Completed in 2014, the renovated interior of the Powerhouse consists largely of open floor plans with minimal closed rooms to allow the building's heating and cooling system to function. The open floor plan and use of interior building materials with hard surfaces created problematic noise levels for the office occupants as noise from laboratory spaces or offices could be heard throughout the building. This project provided a unique opportunity to evaluate the method available to most industrial hygienists to measure and predict reverberant noise: Sabine's Formula and the impulse noise method of reverberation measurement. Reverberation times (RT60) in five interior spaces ranging from 76 m3 to 5400 m3 were modeled using a Sabine's Formula model. The RT60 predictions were then compared to the reverberation times measured in each location, and reverberant noise treatments were designed for two rooms using the same models. The RT60 times were taken again after the installation of the recommended treatments for two rooms. This allowed for the evaluation of both the modeling capabilities of Sabine's Formula and the practical industrial hygiene application of the equation to select effective acoustic treatments to control reverberant noise. The model performed well in room volumes 620 m3 and below, and would have likely performed better in the large volume rooms if they did not have such complex, open acoustic environments. The model was still slightly underestimating reverberation times at 620 m3 indicating that it would perform well in larger volume spaces, though this study was not able to identify the room volume at which Sabine's Formula begins to overestimate reverberation times. The RT60 time reductions in both the first floor classroom and the second floor conference room indicated that the reverberant noise treatment design was successful in reducing the problem acoustics in those areas. The treatment reduced the RT60 times at the problematic low frequencies in both rooms and brought the times near the goal of 0.5-1 second. The researchers found that the Sabine's Formula model is able to adequately predict the reverberant field behavior when different acoustic treatments are applied to the space. The impulse noise method of reverberation measurement is also sufficient to characterize the acoustics of a room to aid in the design and selection of acoustic treatments.Item Open Access Evaluation of seasonal ventilation changes and their effect on ambient dust, endotoxin and bioaerosol concentrations in a dairy parlor(Colorado State University. Libraries, 2011) Funk, Sara, author; Reynolds, Stephen J., advisor; Roman-Muniz, Noa, committee member; Volckens, John, committee memberThis pilot study measured the impact of seasonal ventilation changes on concentrations of organic dust, endotoxin and bacteria in one modern dairy milking parlor. Pyrosequencing, a new non-target specific molecular methodology was used to characterize airborne bioaerosols. Area samples for inhalable dust, respirable dust, endotoxin, and bacteria were collected in one modern dairy parlor during both summer and winter seasons. Five sampling sessions were performed at approximately weekly intervals during each season. The summer season included an open facility with fresh mechanical air ventilation. The winter season consisted of a closed facility with no fresh air ventilation and forced heat. Aerosol size distributions, air velocity inside the parlor, humidity, temperature, and CO2 were also sampled on each trip. Two-way ANOVA was performed to test statistically significant differences between variables. No significant differences between mean concentrations of inhalable dust, respirable dust, or bacteria were seen by season. Endotoxin showed a near significant difference (p=0.06). CO2 concentration doubled during the winter season as compared to the summer (p<0.001) due to reduced ventilation. The aerosol size distribution did not vary between seasons (MMOD=12µm) indicating that seasonal ventilation changes do not affect the particle size distribution. The most common bacterial genera in both seasons were Clostridium (anaerobic), Oscillibacter and Staphylococcus - all Gram positive bacteria. Gram-positive bacterial genera occurred more frequently during the summer than winter seasons. Gram-negative bacteria cell counts increased in the winter season. Average concentrations of total bacteria in the facility during summer and winter were 2839 and 7008 counts/m3, respectively. This study was the first to apply Pyrosequencing to measure bioaerosols in a dairy environment. The diversity of bacteria and predominance of Gram-positive bacteria is consistent with studies in swine and poultry facilities. Concentrations of dust, endotoxin, and bacteria were low during both seasons in this milking parlor, most likely due to the new construction of the facility. These study results will inform the design of future comprehensive studies of aerosol exposure interventions in dairy operations. Understanding these aerosol exposures and potential interventions is important for reducing respiratory disease among workers in the dairy industry.