Emission of bioaerosols from livestock facilities - Methods and results from available bioaerosol investigations in and around agricultural livestock farming
The present report reviews literature from throughout the world on methods and results of bioaerosol investigations in and around agricultural livestock farming and summarises the most important points. The global trend towards intensification and industrialisation of animal production, with regional concentration of livestock facilities and increasing numbers of animals and greater stock densities, has led to an increase in bioaerosol emissions to the environment in certain areas and to increasing concern about health impairment of the population in the vicinity. The main sources of the bioaerosols are the animals and their faeces, the litter and feed. If the particles become airborne, they can be emitted from the stables into the environment. Hundreds of different viruses, bacteria and moulds have been detected in agricultural livestock farming worldwide. The bacterial group of the Staphylococcaceae appears to be most suitable for animal husbandry as a specific indicator or guiding parameter. Bioaerosols can be measured online with particle spectrometers and offline using classical methods, i.e. sampling on site with subsequent evaluation by means of culture-based or molecular biological methods in the laboratory. The classical detection methods are best suited to the complexity of bioaerosols in agricultural livestock farming. The sampling of bioaerosols should be carried out as far as possible using standardised systems that have high physical and biological collection efficiency, in order to ensure comparability of the data. The selection of a suitable collection system should primarily depend on the issue in question. After the bioaerosols have been collected in a sample, evaluation is usually carried out via cultivation and / or various biochemical and molecular biological methods. Especially the latter, in combination with the classical culture-based methods, enable a detailed insight into the composition of bioaerosols. However, further standardisation of the methods for bioaerosols is necessary here. Endotoxins, on the other hand, are predominantly detected using the LAL test, although this test remains relatively susceptible to disturbances. Most data on bioaerosol measurements in agricultural livestock farming available for this review are from the USA and Germany. Here, the concentrations of bacteria, moulds and endotoxins were measured in the stalls of pigs, cattle and chickens. The highest concentrations of airborne bacteria were found in stalls for chickens, followed by turkeys, ducks, sheep, goats, pigs, cattle, horses and rabbits, with the different husbandry and production stages having a significant influence. Emission factors published for airborne microorganisms also differ in part considerably depending on the animal species and the type of keeping, also as a result of different sampling conditions, collection methods and different methods for determination of the concentrations. The concentrations of the airborne bacteria in livestock during the day and night can deviate by a factor of ten. The deviation may further increase by a factor of 1000 if emission factors are calculated on the basis of the specific volumetric flow rates. This must be taken into account in the calculation of annual average values of emission factors. During transportation, i.e. the transport of bioaerosols via the air, the microorganisms are largely exposed to wind and weather...