Reduction of airborne dust, gas and human pathogens in buildings and their environmental dispersion

The objectives of the Animal Housing Environments Projects are to evaluate and decrease levels of incoming and outgoing airborne contamination in swine production (including production facilities and transport of animals) through effective air filtering systems, and positively influence health and economic impacts in the animal production industry by testing means of addressing airborne contaminants including pathogens and bioaerosols.

One of the two projects in this priority area is Air quality in Canadian pig buildings: reduction of airborne dust, gas and human pathogens in buildings and their environmental dispersion. This project aims to characterize, and optimize control or elimination of pathogens and bioaerosols from swine production facilities.

This project involves a national team of researchers, analysts and knowledge translation experts from the Institut de recherche et de développement en agroenvironment (IRDA; Québec, PQ), and Centre de recherche de l’Institut universitaire de cardiologie et de pneumologie de Québec at the Université Laval (CRIUCPQ; Québec, PQ), along with the Canadian Centre for Rural and Agricultural Health, (CCRAH; Saskatoon SK) and the Canadian Agricultural Safety Association (CASA; Winnipeg, MB).

As with the other AgriSafety Program projects, knowledge translation and dissemination of findings will be conducted in conjunction with the Canadian Centre for Rural and Agricultural Health as part of their Knowledge Translation component of the AgriSafety Program. Please visit the "Project Updates" and "Project Output" tabs for information about current activities and Knowledge Translation materials for this project.

Scientific Rationale

The Canadian Pork Council reports the presence of 7,125 pig buildings in Canada, and 1,890 in the province of Quebec (Canadian Pork Council, 2014). There are about 10,000 pig producers in Quebec (MCE conseils, 2014), and consequently thousands of workers are exposed to important concentrations of odorous compounds, gases, and bioaerosols, which are alive or dead bacteria, and microbial fragments for example (Clark et al, 1983; Cormier et al, 1990; Cormier et al, 2000; Donham et al, 1989; Donham et al, 1986; Duchaine et al, 2000; Létourneau et al, 2010a). Odorous compounds, gases, and bioaerosols may be generated from different sources: feed, litter, building materials, animals, and manure. Manure is the main source of bioaerosols as demonstrated by past studies (Nehmé et al, 2008; Pickrell et al, 1993), and may contain human pathogens (D’Allaire et al, 1999). Some of these pathogens are aerosolized and may colonize the nasopharyngeal flora of pig producers (Létourneau et al, 2010b). Furthermore, by ingesting sub-therapeutically doses of metal and antimicrobial agents to encourage their growth, pig are shedding metal and antibiotic resistant bacteria which may also be aerosolized (Masclaux et al, 2013; Létourneau et al, 2010b). From exposure to air of pig buildings, pig producers can develop infectious diseases (Keessen et al, 2013; Poggenborg et al, 2008), and adverse respiratory problems including a decline in lung function, wheezing, chronic bronchitis, and asthma (Cormier et al, 1991; Donham et al, 1984; Iversen et al, 2000). These problems are associated with the number of working hours inside the pig buildings (Radon et al, 2000). Moreover, through the exhaust air, pig buildings emit substantial amounts of airborne contaminants that put farmers and their families at risk, as well as rural communities.

Over the years, different strategies have succeeded in reducing airborne contaminants inside buildings and their environmental emission such as: using feed additives such as soybean oil (Mankell et al, 1995; Welford et al, 1992), cleaning surfaces, spraying oil and soap mixtures into the air (Takai et al, 1993; Zang et al, 1994), employing electrostatic precipitators, separating of liquid and solid phases of manure (Létourneau et al, 2010a), and filtering the exhaust air with chemical scrubbers, bioscrubbers or biofilters (e.g. biotrickling filters).

From our scientific literature review, we found important research gaps that have to be filled: 1) There is a need to complete the characterization of bioaerosols from Canadian pig buildings. For example, there is no data available on the presence of important human pathogens, and metal/antibiotic resistant genes [e.g. Clostridium difficile, Mycobaterium avium, methicillin resistant Staphylococcus aureus, Salmonella spp, Listeria monocytogenes, and zinc and cephalosporin 3rd generation resistance genes]. 2) No study has yet characterized the resulting reduction of bioaerosols (such as bacteria, endotoxins, and human pathogens) of strategies designed to reduce odorous compounds and gases, used individually or in combination.

Aims of Project

  1. Characterize the presence of airborne human pathogens as well as metal and antibiotic resistance genes in buildings and in the nasopharyngeal flora of pig producers.
  2. Correlate the presence of airborne human pathogens and metal and antibiotic resistance genes with usual contaminants found in the air of pig buildings (e.g. total dust, bacteria, endotoxins).
  3. Optimize existing strategies for odorous compound, gas, and bioaerosol reduction (sprinkling oil, separating the liquid and solid phases of manure, and exhaust air treatment with a biotrickling filter).
  4. In a laboratory setup, determine the impacts of optimized strategies on bioaerosols (e.g. total dust, bacteria, endotoxins, human pathogens)
  5. In a laboratory and pre-commercial setup, determine the best combination of strategies and quantify their synergetic effect on odorous compounds, gases and bioaerosols.
  6. In a commercial pig building, validate odorous compound, gas, and bioaerosol reduction strategies.


For further information about this project, please contact Program Manager Nadia Smith at 306-966-1648 or by email at nadia.smith@usask.ca.


References

Canadian Pork Council (2014) http://www.cpc-ccp.com/statistics-farms-e.php site visited on June 1st, 2014

Clark S, Rylander R, and Larsson L. (1983) Airborne bacteria, endotoxin and fungi in dust in poultry and swine confinement buildings. Am Ind Hyg Assoc J 44: 537-541.

Cormier Y, Tremblay G, Meriaux A, Brochu G, and Lavoie J. (1990) Airborne microbial contents in two types of swine confinement buildings in Quebec. Am Ind Hyg Assoc J 51: 304-309. May 2014 Page 3 of 8.

Cormier Y, Boulet LP, Bedard G, and Tremblay G. (1991) Respiratory health of workers exposed to swine confinement buildings only or to both swine confinement buildings and dairy barns. Scand J Work Environ Health 17: 269-275.

Cormier Y, Israel-Assayag E, Racine G, and Duchaine C. (2000) Farming practices and the respiratory health risks of swine confinement buildings. Eur Respir J 15: 560-565.

D'Allaire S, Goulet L, Brodeur J, and Roch G. (1999) Literature review on the impacts of hog production on public health. In Symposium of the Hog Environmental Management Strategy (HEMS). Ottawa, ON: Canadian Pork Council and Agriculture and Agri-Food Canada, pp. 59-62.

Donham KJ, Zavala DC, and Merchant JA. (1984) Respiratory symptoms and lung function among workers in swine confinement buildings: a cross-sectional epidemiological study. Arch Environ Health 39: 96-101.

Donham KJ, Popendorf W, Palmgren U, and Larsson L. (1986) Characterization of dusts collected from swine confinement buildings. Am J Ind Med 10: 294-297.

Donham K, Haglind P, Peterson Y, Rylander R, and Belin L. (1989) Environmental and health studies of farm workers in Swedish swine confinement buildings. Br J Ind Med 46: 31-37.

Duchaine C, Grimard Y, and Cormier Y. (2000) Influence of building maintenance, environmental factors, and seasons on airborne contaminants of swine confinement buildings. Am Ind Hyg Assoc J 61: 56-63.

Iversen M, Kirychuk S, Drost H, and Jacobson L. (2000) Human health effects of dust exposure in animal confinement buildings. J Agric Saf Health 6: 283-288.

MCE conseils (2014) Impact économique de la filière porcine.

Keessen EC, Harmanus C, Dohmen W, Kuijper EJ, and Lipman LJ. (2013) Clostridium difficile infection associated with pig farms. Emerg Infect Dis 19: 1032-1034.

Letourneau V, Nehme B, Meriaux A, Masse D, and Duchaine C. (2010a) Impact of production systems on swine confinement buildings bioaerosols. J Occup Environ Hyg 7: 94-102.

Letourneau V, Nehme B, Meriaux A, Masse D, Cormier Y, and Duchaine C. (2010b) Human pathogens and tetracycline-resistant bacteria in bioaerosols of swine confinement buildings and in nasal flora of hog producers. Int J Hyg Environ Health 213: 444-449.

Mankell KO, Janni KA, Walker RD, Wilson ME, Pettigrew JE, Jacobson LD. and Wilcke WF. (1995) Dust suppression in swine feed using soybean oil. J Anim Sci 73: 981-985.

Masclaux FG, Sakwinska O, Charriere N, Semaani E, and Oppliger A. Concentration of airborne Staphylococcus aureus(MRSA and MSSA), total bacteria, and endotoxins in pig farms. Ann Occup Hyg 57: 550-557.

Nehme B, Letourneau V, Forster RJ, Veillette M, and Duchaine C. (2008) Culture-independent approach of the bacterial bioaerosol diversity in the standard swine confinement buildings, and assessment of the seasonal effect. Environ Microbiol 10: 665-675.

Pickrell JA, Heber AJ, Murphy JP, Henry SC, May MM, Nolan D, et al. (1993) Characterization of particles, ammonia and endotoxin in swine confinement operations. Vet Hum Toxicol 35: 421-428.

Poggenborg R, Gaini S, Kjaeldgaard P, and Christensen JJ. (2008) Streptococcus suis: meningitis, spondylodiscitis and bacteraemia with a serotype 14 strain. Scand J Infect Dis 40: 346-349.

Takai H, Moller F, Iversen M, Jorsal SE, and Billehansen V. (1993) Dust control in swine buildings by spraying of rapeseed oil. Livestock Environ IV. 93: 726-733

Welford RA, Feddes JJR, and Barber EM. (1992) Pig buildings dustiness as affected by canola oil in the feed. Can Agr Eng 34: 365-373.

Zhang Y, Nijssen L, Barber EM, Feddes JJR, and Sheridan M. (1994). Sprinkling mineral oil to reduce dust in pig buildings. Transactions of ASHRAE, 100: 1043-1052.

Year 1 (2014-15) Update

During the first year of the project, the two following activities were scheduled to take place:
1. Recruitment of swine producers as well as pig buildings;
2. Development of PCR protocols to evaluate the presence of some clinically important human pathogens and resistance genes for certain antibiotics and metals.
At the beginning of the project, a monitoring committee was set up to make sure the project objectives and the protocol represent adequately the needs of the swine industry. The committee is composed of pig producers, members of agricultural associations as well as other interest groups. During the first meeting, the monitoring committee was consulted to determine the criteria used for the recruitment of the swine producers and pig buildings. The different criteria were defined as follows:

  • Pig buildings must be representative of the Canadian and Quebecois swine industry;
  • The characteristics of the pig buildings should be as uniform as possible: o Buildings for grower-finisher pigs with fully slatted floors
  • Buildings housing 1 200 to 1 600 pigs with standard mechanical ventilation
  • Selected sites must be free of any sicknesses
  • Pig producers must be non-smokers that work exclusively in grower-finisher buildings o The time selected producers spend inside pig buildings must be well documented
In order to encourage producers to participate in this project, the monitoring committee suggested to provide participants with a small monetary incentive and to have biosecurity precautions and sampling procedures approved by a veterinarian. Also, groups of producers or swine integrators will be used to accelerate the recruitment process.
Regarding the development of Polymerase Chain Reaction (PCR) protocols, a literature review was first performed to confirm our choice of clinically important human pathogens (species to sub-species) and resistance genes for antibiotics and metals. The original list of airborne human pathogens studied in this project was amended to include other relevant microorganisms. From the literature review, specific genes were chosen to evaluate the presence of zinc and third generation cephalosporin resistant microorganisms in the air of Canadian pig buildings. Finally, standard curves are being developed for quantitative PCR protocols (construction of plasmids).

Year 2 (2015-16) Update

During the second year of the project, the research team achieved two significant milestones:

  1. The appropriate microbiological tools were developed in order to characterize the presence of airborne human pathogens and metal and antibiotic resistance genes in both pig buildings and the nasopharyngeal flora of swine producers. These tools will be used by the research team to evaluate the presence of several important pathogens: Clostridiurn difficile, Salmonella spp., Listeria monocytogenes, Mycobaterium avium, Methicillin resistant Staphylococcus aureus and resistance genes for Zinc and 3 generation cephalosporin.
  2. A laboratory-scale system was installed in the BABE Laboratory to test the combination of four technologies to reduce odours, gas, dust and bioaerosol emissions from pig buildings. The different technologies were optimized to overcome certain operational problems and to improve performance. The unique facilities of the BABE Laboratory are currently being used to test all the possible combinations of the technologies in order to determine the optimal configuration to be used in commercial-scale pig buildings.

A new Knowledge Translation bulletin entitled "Techniques to Control Odorous Compounds, Gas and Bioaerosols in Swine Buildings" (16-03-012) has been published regarding this project. It can be viewed under the "Project Output" tab.

Year 3 (2016-17) Update

Preliminary results from the samples collected from the air of the different pig buildings revealed the presence, in one or more of the buildings, of each pathogen and each resistance gene that the research team tested. Regarding the laboratory-scale tests used to evaluate the performance of the contaminant reduction technologies, it was determined that all three technologies must be used together to adequately protect worker health and limit environmental emissions.

With the complete results obtained during this project, it will be possible to evaluate the risk of exposure of swine producers and workers to human pathogens as well as metal and antibiotic resistant microorganisms. It will also be possible to offer an efficient strategy to reduce airborne contaminants within swine buildings and improve both air quality and worker health. 

The main objective that was completed in Year 3 of the project was Objective 3 - The final tests at the BABE Laboratory evaluate the effect of the three contaminant reduction technologies used alone and in combination with one another. A detailed analysis of the results for odour, gas, dust and bioaerosol removal was conducted to determine the best combination of contaminant reduction technologies.

The results from objective 3 were analyzed in order to determine the best combination of airborne contaminant reduction technologies to be used in the commercial-scale tests of objective 4. The three technologies tested were selected to be implemented in objective 4. The air treatment unit and oil sprinkling can easily be added to any existing building, but the v-shaped scraper for manure separation must be installed under the slatted floor and it is not possible to install the required equipment within the scope of this project. Therefore, an existing building must already be equipped with the v-shaped scraper for it to be tested. This technology was selected for manure separation since a few pig buildings in Québec were known to have used the system. However, preliminary enquiries have shown the difficulty of finding a building still equipped with the v-shaped scraper. An alternative solution will be required if it is not possible to find an existing building equipped with the v-shaped scraper. The IRDA farm in Deschambault has two pig rooms that could be adapted for objective 4 of this project. This would change the scope of objective 4 as a commercial barn was intended, but the rooms at IRDA are representative of commercial-scale installations and it would be possible to test manure separation. 

Year 4 (2017-2018) Update

Over the years, different strategies have succeeded in reducing airborne contaminants inside buildings and their environmental emissions, but no study has yet characterized the resulting reduction of bioaerosols, nor if any synergetic effect can be obtained from the combination of these technologies. The main objective of this project is to offer the swine industry an efficient strategy to reduce airborne contaminants and protect the health of workers. The activities for the fourth year of the project are detailed below for each specific objective:

  • Objective 1 = Evaluate the presence of human pathogenic agents and antibiotic and zinc resistance genes in the air of commercial pig buildings and in the nasopharyngeal flora of pig workers.
    • The nasopharyngeal flora of 25 pig workers and of 30 non-exposed subjects were sampled by swabbing and analyzed by PCR targeting human pathogenic agents and resistance genes and by next generation sequencing. The studied human pathogens (Clostridium difficile, Listeria monocytogenes, Staphylococcus aureus, and methicillin-resistant S. aureus) and antibiotic (cephalosporin 3rd generation and colistin) and zinc resistance genes were more frequently detected in the nasopharyngeal flora of pig workers than in non-exposed subjects. Next generation sequencing revealed a bacterial diversity specific to workers. The nasopharyngeal flora of workers may then constitute a marker of exposure to bioaerosols from pig buildings.
  • Objective 2 = Optimize the design of airborne contaminant reduction strategies: oil sprinkling, liquid and solid separation of manure and air treatment with a biotrickling filter.
  • Objective 3 = Using laboratory scale pig buildings, measure the reduction of odorous compounds, gases, dust and bioaerosols from the use of the 3 studied airborne contaminant reduction strategies in order to determine the best combination of strategies.
  • Objective 4 = Evaluate the reduction of airborne contaminants using the best combination of strategies in a commercial-scale building.
    • Two pre-commercial pig finishing rooms were built for this part of the project, each containing 16 pigs from 25 to 90 kg. A standard room was compared to a room equipped with a combination of the 3 airborne contaminant reduction strategies over two, 7-week tests. Odorous compounds, gases as well as total dust, endotoxin and bacteria were sampled.
    • By combining the 3 contaminant reduction technologies (oil sprinkling, manure separation and exhaust air treatment), it was possible to reduce the emissions of odours, gas and dust. However, the v-shaped scraper used for manure separation didn’t provide the expected reduction in ammonia emissions. For bioaerosols, reduction efficiencies were observed in the room with oil sprinkling and manure separation for total dust, culturable bacteria as well as total endotoxin and bacteria (PCR). The biotrickling filter helped reduce total dust but no reduction of culturable bacteria was observed due to the biologically active system.

During the fourth year of the project, the research team achieved two noteworthy results:

  • The results from Objective 1 revealed that distinguishing the nasopharyngeal flora of pig workers from that of non-exposed subjects is possible by targeting specific human pathogenic agents by PCR and by sequencing 16S rRNA genes in samples. The nasopharyngeal flora could therefore be an excellent marker of exposure to bioaerosols, and, consequently, a way to evaluate health risks in a working or residential environment without doing any air sampling. Air sampling implies specialized staff and expensive equipment. These results need to be confirmed by sampling and sequencing 16S rRNA genes of nasopharyngeal flora from workers exposed to bioaerosols of other agricultural, industrial and non-industrial environments.
  • Two pig rooms were custom built to compare the combination of the 3 airborne contaminant reduction technologies to an industry standard room. Each room can contain 16 pigs from 25 to 90 kg and is equipped with commercial ventilation and feeding systems. Two tests were carried out where odorous compounds, gases as well as total dust, endotoxin and bacteria were sampled.

The results obtained in this study provide valuable insight as to the presence of human pathogenic agents and resistance genes in the air of commercial pig buildings as well as to the performance of technical strategies to reduce the health risks.

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