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Bioaerosols : Tiny particles, big effect

Von Marcus Clauß | 01.07.2022

AT Institute of Agricultural Technology

In addition to gaseous emissions livestock also releases airborne microorganisms such as bacteria or molds. These bioaerosols are suspected to affect the health of residents in the immediate vicinity of stables. The evidence is still insufficient, but many questions remain unanswered.


While we only inhale a few bacteria with one breath of fresh air, there may be millions of bacteria in a breath full of air in large livestock barns. Airborne bacteria are only a small part of the so-called bioaerosols. These consist of a complex mixture of various biological components, ranging from simple organic molecules with dimensions in the nanometer range of viruses, bacteria and fungal spores to pollen of 0.1 millimeters in diameter, as well as animal and plant residues of different sizes.

This "biological dust" usually forms larger aggregates, to which also odorants or ammonia can be bound. Therefore, we always look at the emissions of bioaerosols "holistically", along with dust, ammonia and odors.

Bioaerosols are found in the vicinity of the stables and in the surrounding environment  as they exit via the stable exhaust. Especially in systems with tens of thousands of animals, these emissions into the immediate vicinity of the stables could lead to health problems. However, there is currently no sufficient evidence that residents are at risk, but many questions are still open, to which the Institute of Agricultural Technology will dedicate itself in the future.

Post colorized SEM images

With scanning electron microscopy particle surfaces can be shown with high depth of sharpness. The maximum magnification is up to 100,000-fold. The post-colorizing of the grayscale images allows better discrimination of the different particles.


Colour code:
brown = filter material; orange = mold spores; yellow = mold hyphae; green = particle of plant origin; red = particle of animal origin; magenta = bacteria; blue = unidentified particle


Transmitted-light microscopy

In transmitted-light microscopy the light goes directly through the probe. This method is especially suitable for the identification of mold spores and pollen. Bacteria appear nearly transparent so they cannot be viewed very well with this method.


Fluorescence microscopy

In fluorescence microscopy different dyes were selectively bound to microorganisms. When irradiated with uv light they shine very bright and we can discriminate them from the background. With this method we investigate the inner structure of the bioaerosol particles.

For this procedure the particles have to stick at the substrate so that they not be washed away by the dye solution. Therefore we collect the particles by means of an impactor directly from the air onto special adhesive silicone surfaces.

With our fluorescence dyes we stain the DNA of the bacteria which shine green to orange when irradiated with uv light. Not only bacteria shine in this way because other particles also contain DNA, however we can recognize them on their characteristic sphere or rod like shape.



What are the sizes of bio-aerosols?

“What is the size of bio-aerosols?” The answer to this question is not easy to give, because bio-aerosol particles are composed of many different components as viruses, bacteria, moulds, pollen and debris of plants and animals, each with different sizes. It is an important question, too, because the effects of bio-aerosols on human health are depending also on the particle size. For example, large bio-aerosol particles get already stuck in the nose or mouth which may cause a common cold, but small particles can get deep into the lungs and in the worst case may induce pneumonia.

What are the sizes of bio-aerosols?

Tracing the flight of bioaerosols

Planned construction of animal housings lead more and more often to resistance in the local population. The reason: Emission of bioaerosols. We develop measuring systems to collect valid data and provide them for health assessment.

Tracing the flight of bioaerosols

How good is the air quality in animal houses?

Poor air quality in stables can harm the respiratory ducts of farm animals; lung function impairment is also a recognised occupational disease of farmers and veterinarians. We investigate the composition of air in animal houses to improve air quality and prevent diseases.

How good is the air quality in animal houses?

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