# Advanced Strategies for Mitigating Particulate Matter Generations in Poultry Houses
###### Abstract  
Poultry farming plays a key role in agricultural air emissions. Particulate matter (PM) level tends to be high in broiler and cage-free layer houses, that may impair health and welfare of animals and their caretakers. To protect public health and welfare, the occupational exposure limit for PM\({}_{10}\) and PM\({}_{2.5}\) (i.e., PM diameters that are generally \(\leq\)10 and 2.5 \(\upmu\)m, respectively) are suggested not to exceed 150 \(\upmu\)m\({}^{-3}\) and 35 \(\upmu\)m\({}^{-3}\), respectively, based on 24-h concentrations thresholds as suggested by US. EPA. However, the levels of PM\({}_{10}\) and PM\({}_{2.5}\) in poultry houses could be 100 times higher than that limit. For instance, PM\({}_{10}\) and PM\({}_{2.5}\) levels in cage-free henhouses are higher than 15,000 \(\upmu\)m\({}^{3}\) and 3500 \(\upmu\)m\({}^{3}\) in wintertime. Therefore, it is critical to identify the primary factors affecting PM generation in poultry houses and apply corresponding mitigation strategies. This review paper summarizes PM emission factors, mitigating strategies, and impacts on birds' and caretakers' health, and welfare. Generally, PM emissions are affected by various factors, including housing types, seasonal and diurnal variation, manure management, bedding materials, ventilation rates, and birds' activities. High PM concentrations in poultry houses impair birds' and caretakers' liver, kidneys, and respiratory systems. Thus, different mitigating strategies are discussed in this study for addressing those issues. Effective mitigation strategies include frequent house cleaning, optimum light intensity, liquid spraying, bedding management, and air filtration systems. However, mitigation strategies can be cost-prohibitive and have side effects. Therefore, poultry farms should select mitigation strategies based on farm location, climate conditions, environmental policies, and available resources (government assistance programs).  
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Particulate matters in confined animal housing are heterogeneous combinations of biologically generated materials and aerosolized pollutants such as feed additives, broken feather pieces, dried NH\({}_{3}\), viable and nonviable bacteria, endotoxins, glucans, molds, and fungal spores [16; 17; 18]. In poultry houses, the primary sources of PM include feathers, feeds, urine mineral crystals, manure, and bedding materials. The PM generated from these sources shows harmful effects on the health of animals and careakers [19; 20]. For example, in birds, higher PM levels result in an increased risk of chronic bronchitis, cardiovascular illness, pneumonia lesions, asthma-like symptoms, and lung cancer [21; 22], while in caretakers, it causes bronchitis, asthma, and organic dust toxic syndrome [20]. In addition, poultry farm workers are usually at high risk of occupationally being exposed to many respiratory problems leading to higher asthma rates or other respiratory symptoms at work [23].  
This review study aims to discuss various factors that affect PM emissions and potential strategies to reduce its generation from poultry production systems. Therefore, the primary objectives of this study were to (1) summarize factors that affect PM or dust levels in poultry houses, (2) analyze potential strategies for mitigating PM generations, and (3) discuss the pros and cons of different methods and expectations on new strategies to improve air quality and health and welfare of animals and their caretakers.