In Canada, livestock (swine, cattle) and poultry are now more often concentrated and confined in large operations. Millions of tons of waste are produced annually and spreading of manure has never been closer to urban developments. In 2006, the Canadian livestock industry produced about half a million tons of manure daily. Although manure spreading benefits crop production, it can be a source of pollution with impacts on the environment as well as human and animal health. For example, bacteria found in manure have been detected in drinking water supplies. The use of manure as a crop fertilizer has also been associated with odour nuisances and gases as well as the contamination of fruits and vegetables with foodborne pathogens. Public concern has consequently increased regarding the impact of manure spreading on human and animal health. Even if underestimated, there is a significant health risk associated with the fugitive emissions following manure spreading. Human and animal pathogens and antibiotic-resistant bacteria are present in wastes and may potentially be aerosolized in large quantities when spreading on agricultural lands. Once airborne, these contaminants can then affect the health of workers, animals, and surrounding rural communities.
Many regulatory authorities dictate minimal setback distances for manure spreading near houses or other buildings. However, these requirements are generally based on nuisances for the surrounding populations and do not take into account the health risks associated with manure spreading.
A variety of contaminants from animal husbandry have been identified due to their potential to be present at sufficient concentrations to affect human health: ammonia (NH3), hydrogen sulphide (H2S), odours, respirable dust, and bioaerosols. These contaminants are generally associated with animal buildings, but they can also be emitted in large quantities following manure spreading. NH3, H2S, and certain odorous compounds can be irritant or even toxic for humans. NH3 also contributes to the formation of fine particulate matter (PM) that is linked to human respiratory problems. For NH3, H2S, and dust, most governments impose strict limits on workplace exposures. These concentration recommendations are often exceeded in livestock buildings, and they must be measured during manure spreading operations to make sure they don’t exceed the acceptable limits. Furthermore, these limits do not consider the cumulative effect of these contaminants, which can increase the health risks for workers and rural populations.
Odours can also have various psychological effects on rural populations, such as tension, depression, anger, and a decrease in vigour, fatigue and confusion. The cumulative and synergistic effects of contaminants (gases, dust, and microorganisms) and odours can represent increased risks, however still misunderstood, for rural populations. The nuisance and the perceived health risks associated with agricultural odours can seriously undermine the social acceptability of the livestock industry.
Regarding airborne microorganisms, a few zoonotic agents are considered in the literature to be of concern following manure spreading on agricultural lands: Campylobacter sp., Clostridium perfringens, verotoxigenic Escherichia coli, Listeria monocytogenes, Salmonella spp. and Yersinia enterocolitica. Symptoms of nausea, abdominal cramps, vomiting or diarrhea are usually associated with these pathogenic agents, but morbidity and mortality can occur in some infected humans or animals.
The potential risks are greatly increased when the resilience of some of these pathogens is considered. For example, the persistence of Salmonella can be counted in months in slurry and soils and in aquatic environments for the pathogenic agent Campylobacter. As a spore-forming organism, Clostridium perfringens is likely to be a long-time survivor in manure. E. coli O157: H7 may persist up to 2 months in manure. For Listeria monocytogenes, its ability to grow at low temperature (e.g. 4oC) in high (up to 12%) salt concentrations and at a range of pH from 5.5 to 9.0 contributes to its environmental persistence.
Even if understudied, manure is considered as a vehicle to disseminate animal viruses such as the porcine reproductive and respiratory syndrome virus (PRRSV), the foot-and-mouth disease virus, the bovine viral diarrhea virus, the swine influenza virus, and the porcine parvovirus. All these animal viruses represent an economic burden for the Canadian livestock industry.
Inside livestock operations, aerosolization of zoonotic agents, antibiotic-resistant bacteria and viruses from manure are possible and have been demonstrated. However, notwithstanding the risks described here with the contaminants found in manure, there is a lack of knowledge on airborne contaminants associated with manure spreading and the risks are not well understood. Moreover, the few studies that have evaluated the emission of pathogenic agents used culture-dependent approaches or low volume air samplers, not suitable for outdoor sampling, and did not quantify emissions in standardized or environmentally-controlled conditions (e.g. using a portable wind tunnel). Furthermore, the type of manure spreading equipment (solid manure, splash plate or dribble bar for liquid manure) plays an important role in airborne emissions by influencing the exchange rate between manure and air. Once the risks are quantified, solutions limiting emissions from manure spreading can be put in place to protect the health of workers, animals and neighbours.
Aims of Project
The specific aims of this project:
- Quantify emissions of airborne contaminants following manure spreading.
- Evaluate the health risks associated with these fugitive emissions for workers, animals, and rural communities.
- Determine the best strategies to mitigate the risks and test the performance of these strategies in field conditions.
The results from this project will fill the gap in knowledge regarding airborne emissions from manure spreading activities and provide solutions to reduce the risk to human health.
2019 - 2020 Year 1 Update
Manure spreading on agricultural lands is a common practice but carries health risks for workers, livestock and rural communities. Dust, gases, odours and bioaerosols such as human and animal pathogens and antibiotic-resistant bacteria are present in manure and may potentially be emitted in large quantities following manure spreading. Once airborne, these contaminants can then affect the health of workers, animals, and surrounding rural communities. The overall goal of this project is to assess the risks associated with manure spreading and determine the best strategies to mitigate these risks.
In Year 1, the IRDA research team developed passive flux samplers (PFS) to capture nitrous oxide (N2O) and to measure emissions. The PFS is comprised of two tubes with a hole in between to make sure the air velocity inside the sampler matches the outside wind velocity. A sorbent is placed in the tubes to capture all the target gas during the sampling period. Once gases are captured by the PFS, they are desorbed and measured in the laboratory. The research team began work on a PFS design to sample ammonia (NH3), nitrous oxide (N2O), and carbon dioxide (CO2). However, there is still work to do before the samplers are ready to test in the field. The Quebec Heart and Lung Institute (CRIUCPQ) team has extensive expertise in environmental air sampling with high volume samplers combined with molecular biology and high throughput sequencing. Once the bioaerosol samples are collected, a thorough microbiological analysis will be carried out for total bacteria, human pathogens, animal pathogens and antimicrobial resistance genes to help identify the hazards resulting from the aerosolization of manure emissions.
Work was started on the construction of a field-scale wind tunnel to be used for validation of new sampling techniques in comparison to traditional sampling methods. The wind tunnel consists of a plastic tarp fitted over a metal frame and installed securely to the ground to prevent the loss of emissions from the sides. The environmental conditions (wind speed, temperature and humidity) will be closely monitored in the tunnel. Standard equipment for gas sampling and analysis will be installed on the site to analyze the gases (H2S, NH3, N2O and CO2, CH4), particulate and odour concentrations at the inlet and the outlet of the wind tunnel. The airflow rate will be used to calculate emissions.
2020 - 2021 Year 2 Update
In Year 2, the research teams of Research and Development Institute for the Agri-Environment (IRDA) and the Institut universitaire de cardiologie et de pneumologie de Québec – Université Laval (IUCPQ-UL) established a protocol and the experimental setup to best measure the fugitive emissions resulting from manure spreading.
The wind tunnel is a greenhouse with a polycarbonate covering that is being used as a controlled environment for measuring the emissions of contaminants from manure spreading. The greenhouse mimics a wind tunnel, with 10 fans are installed at one end of the tunnel and two openings on the other end. The speed of the fans can be controlled individually to change the air pattern and flow rate in the greenhouse. This variable airflow rate allows for the measurement of large emission ranges of gas, dust, odours and bioaerosols at the outlet of the greenhouse. Environmental conditions, including temperature, humidity and wind speed, are monitored continuously in the greenhouse during the experiments.
Inside the greenhouse, a small-scale soil plot has been built and is filled with soil on which manure will be spread. Two types of manure will be spread: 1) solid cow manure, using a small ground-driven manure spreader with horizontal paddles, and 2) liquid pig slurry, using a 4.5 m low spreading toolbar with deflectors, applying slurry by gravity over the soil. The spreading equipment will be pulled using a winch installed at the extremity of the greenhouse.
The sampling process will be carried out from the onset of manure spreading trial until a few hours following the application, gases will be sampled continuously for analysis of ammonia (NH3), nitrous oxide (N2O), methane (CH4), carbon dioxide (CO2) and hydrogen sulphide (H2S) concentrations. The emissions will be calculated by multiplying the airflow rate in the greenhouse by the gas concentrations, which is a conventional technique to measure emissions from a farm building. In parallel, passive flux samplers (PFS) will be installed in the greenhouse for the measurement of gas emissions. The PFS consists of two tubes with a hole in between so that the air velocity inside the sampler is equal to the outside wind velocity. An absorbing material is placed in the tubes to capture gas molecules. After the sampling period is complete, the captured gases are extracted from the absorbent material and quantified in the laboratory.
Odours will be sampled at the outlet of the wind tunnel using a bag filled with a low flow rate electric pump to collect average samples over time. Smaller bags powered by a battery will be tested for comparison and further use in the field. The odour concentration will then be analyzed by olfactometry using a human panel.
2021 - 2022 Year 3 Update
In Year 3, six spreading repetitions were done with both solid cow manure and liquid pig slurry using the large-scale wind tunnel specially constructed for this project. This unique experimental facility doesn’t exist anywhere else in the world and provides the opportunity to reproduce field-scale activities in a completely controlled environment. For solid manure, a small horizontal beater spreader was used while a custom splash plate aspersion spreader was built to broadcast pig slurry 1 m over the soil. Both spreaders were pulled by a low-power tractor. To avoid interference with air contaminants emitted from manure spreading, the combustion gases were evacuated outside the wind tunnel.
Results from gas analyses following liquid pig slurry spreading showed that carbon dioxide (CO2) and methane (CH4) concentrations increased right after spreading, before decreasing quickly within 5 minutes. Ammonia (NH3) concentrations started to increase progressively a few minutes after the spreading and decreased slowly during the next hour. For solid manure spreading, gas emissions were very low and not detectable for most of the gases.
Bacteria and dust analyses revealed that, with both solid and liquid manure, the concentration of total bacteria as well as the average total dust increased with the start of the spreading, before decreasing rapidly after spreading. A similar trend was observed for odor intensity and concentration. Finally, ratios of antibiotic resistance genes/bacterial loads are under analysis.
Additional tests will be carried out in the controlled environment in year 4 to generate more data with different types of manure and spreaders before moving on to the intensive field sampling campaign.
2023 - 2024 Year 5 Update
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