**4. Particulate matter**

In broiler housing, the PM consists of a complex mixture of solid and liquid materials such as litter materials, feathers, feeds, skin, excreta, dander and microorganism, whit about 90% organic content [41]. The classification of PM is based on particle size (aerodynamic diameter), considering PM1.0 (≤1.0 μm), PM2.5 (≤2.5 μm), PM4.0 (≤4.0 μm), PM10.0 (≤10.0 μm) and total suspended particle (TSP) (≤100.0 μm) [42]. The PM emissions from broiler housing are affected by various factors and change according to housing system or types, litter materials, diurnal and seasonal variation, ventilation system and velocity, temperature and relative humidity, birds age and type, activity and stocking density and manure management (**Figure 2**) [41].

The primary air emissions include PM with a high potential risk to air quality, public and bird health, and climate change. Cambra-López et al. [43] reported that the concentrations of TSP (inhalable PM) in broiler houses ranged from 1 to 14 mg m−3 in European countries. The World Health Organisation has recently (in 2021) amended the ambient air quality standards and proposed the maximum of PM10.0 to be 15 μg m−3 for the annual average and 45 μg m−3 for the 24 h mean, while for PM2.5 to be 5 μg m−3 for the annual average and 15 μg m−3 for the 24 h mean [41]. In Portugal, the Directive 2016/2284/EU establishes a 53% reduction of PM2.5 from 2030 compared to 2005 levels. The levels of PM in broiler houses affect birds' health and welfare, including eye irritation, throat irritation, cough, phlegm, chest tightness, sneezing, headache, fever, nasal congestion, and wheezing, especially in cold periods when the house will have limited ventilation. Furthermore, long term exposure to PM in humans increases obstructive pulmonary disorder, chronic bronchitis, chronic obstructive pulmonary disease, pneumonia lesions, cardiovascular disease, asthma like symptoms, lung cancer, or even mortality. Similarly, a higher level of PM with endotoxin in birds causes impaired lung function, chronic bronchitis, pneumonia lesions, cardiovascular illness, and cardiotoxicity in chicken embryos and hatchling chickens and might increase the risk of mortality rates [21, 41, 43].


#### **Table 3.**

*Best available technologies for mitigation of airborne pollutants in broiler houses (from Ni [28]).*

*Review of Measures to Control Airborne Pollutants in Broiler Housing DOI: http://dx.doi.org/10.5772/intechopen.110582*

**Table 3** show effective mitigation strategies to reduce PM in broiler houses using biochemical, chemical, managerial, physical, and physiological practices. The techniques to control PM will also reduce NH3 and odours, which can be managing housing system and cleaning, light intensity, oil and water spraying, litter materials, electrostatic ionisation, filtration and biofiltration, acid scrubber, windbreaks and vegetative shelterbelts [28, 41, 43, 44].
