The recent outbreak of avian influenza, a highly contagious viral disease that has infected about 48 million birds in the United States, resulted in a significant loss to the poultry industry. The initial response by the poultry industry to prevent widespread avian influenza was to more stringently enforce the USDA biosecurity measures defined by the USDA Animal and Plant Health Inspection Service (APHIS) (http://healthybirds.aphis.usda.gov). However, the continuous spread of the avian influenza made the industry wonder if the disease is airborne and transmitted through ventilation air of poultry facilities. We are looking at major air emissions — ammonia gas and dust particles — from poultry facilities and their potential effects on poultry health to explore the need of additional biosecurity measures to prevent transmission of infectious diseases among poultry in the future.
Ammonia emissions and its health effects
Ammonia is a colorless, irritant gas that is produced from the microbial decomposition of uric acid in poultry manure. NH3 levels can vary from 10 to 80 parts per million (ppm) in poultry houses and are affected by feed protein level, manure management, building facility and ventilation system, bird type and age, and seasonal and diurnal weather conditions. Due to the fact that poultry facilities use ventilation to control indoor air temperature, ammonia concentration in poultry buildings has strong seasonal and diurnal variations and typically is the highest in winter. In addition, ammonia levels in poultry houses are highly dependent on the manure removal and storage system.
High ammonia levels indoors are considered a health hazard. Due to its high chemical reactivity, ammonia is a very strong irritant. Exposures to low levels of ammonia usually cause slight eye, nose, and throat irritation. Exposure to ammonia higher than100 ppm can cause more severe irritation of eyes, nose and throat. Higher levels of ammonia exposure can cause keratoconjuctivitis, impaired mucus flow, and ciliary reaction in the trachea. Moreover, there is an increased susceptibility to respiratory disease and secondary infections with high levels of ammonia exposure. High ammonia levels may also indirectly cause lower body weights, reduced feed efficiency, and a decrease in egg production in laying hens.
Dust in poultry houses
Dust is often called particulate matter (PM) and when it is biologically active, it is also called bioaerosol. PM is categorized into TSP (total suspended particles), PM10, and PM2.5 (dust particle with aerodynamic diameter less than 10 μm and 2.5 μm, respectively). PM10 and PM2.5 are criteria air pollutants regulated by National Ambient Air Quality Standards (NAAQS) defined in the Clean Air Act. From a health point of view, PM is also categorized as inhalable dust (PM with a diameter less than 100 μm), respirable dust levels (PM with a diameter less than 4 μm), and thoracic dust (4 μm less than PM with a diameter less than 100 μm).
PM10 concentrations in poultry houses range from 0 to 4.5 mg/m3 and PM2.5 data is very limited now. Inhalable dust levels in poultry houses range from 4.8 to 20.2 mg/m3 and the respirable dust levels range from 0.19 to 1.8 mg/m3. The OSHA PEL (permissible exposure limit) for TSP is 15 mg/ m3 and for respirable dust is 5 mg/ m3. PM concentrations in some poultry buildings can sometimes exceed the OSHA indoor air quality standard.
Dust particles host bacteria and virus
Dust in poultry houses is classified as organic dust and considered to be biologically active compared to inorganic dust. Poultry dust contains food, fecal material, broken feather barbules, skin debris, fungal fragments and spores, bacteria and bacterial fragments, viruses, and particles of litter, with skin debris and feather barbules being the major constituents in caged layer dust.
Bacteria are generally 1-2 µm (micrometer) in diameter and associated with respirable dust particles. Viruses and bacterial rarely remain viable in an isolated state and in air and are usually attached to inert host particles that are lager than the organisms. Therefore, dust particles play a crucial role in the dispersal, survival and deposition of airborne pathogens in animal buildings. Dust at animal facilities can contain enteric pathogens (e.g. Salmonella, Campylobacter, pathogenic E. coli) and virus (such as avian influenza).
Dust affects health
The microbial fraction of dust is of fundamental importance to health as it can be a causative agent of disease. After reviewing the composition and high level of dust concentrations in poultry facilities, it is not surprising to see that dust emissions from poultry facilities could act as biohazard carriers and have been primarily associated with respiratory illnesses such as bronchitis, organic dust toxicity syndrome (ODTS), hyper-reactivity airway disease, chronic asthma, and membrane irritation. Animal health and productivity can also be reduced by excessive dust exposure. Researchers have linked increased bird mortality to high dust concentrations in an enclosed laying house.
Furthermore, dust (when combined with other air contaminants such as ammonia) has been documented to enhance respiratory diseases in poultry, increase mortality rates, and reduce bird growth. Dust irritates the respiratory tracts of birds and ammonia gas acts as a chemical irritant. The mechanical irritation of dust to the respiratory epithelium, its interference with mucous production and its damage to the cilia lead to an increased susceptibility to infection by aerosolized microbes, such as E. coli, which might not otherwise have an impact on the bird’s health.
In summary, dust and ammonia emissions in poultry buildings affect health. Control of ammonia and dust levels in poultry houses may become very necessary for reduced transmission of infectious disease, such as avian influenza, and improved health. A group of researchers at Department of Food, Agricultural and Biological Engineering of The Oho State University is actively developing and field-testing effective engineering technologies to control ammonia and dust emission at poultry facilities, such as ammonia wet scrubber and electrostatic precipitation based dust control devices. See airquality.osu.edu for more detailed information.